Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Hi all:
Yesterday, Celestron upgraded my old AS CG5 GT Hand Control Device with the newest software, versions 4.15 and 4.16, by replacing the old HC with a brand new HC device which contained the newest software installed in it.
According to the Celestron's literature (and the internet astro discussions); the newest software will create a far better model of the sky which is supposed to result in greater precision for tracking and pointing of the telescope.
Since my SCT is used in the same location in the southern California desert, I would like to use the new software to create the best possible sky model which would result in the most precise pointing for the upcoming Spring and Summer. If I recall properly I believe that Celestron's literature further states that the new software gives the Mount a greater ability to remember the sky model that was created; which information is or may be saved in the Mount's memory; and, can be thereafter improved upon with subsequent calibrations in the course of further modelling of the sky.
I am certain that many of you who have the luxury of a permanent observatory have considered these issues as well. Towards that end, I am wondering which alignment procedure(s) would be most effectively utilized with this new software by incorporating which alignment and which calibration stars to create the best model of the sky for the computerized Goto of the AS CG5 GT Mount.
Any such tips, pointers, suggestions or other such help would be much appreciated.
Currently, I am thinking of the following procedure:
1.) Polar Align it as accurately as possible in the intial set-up with bore sighting Polaris through the Mount's hole; and, use the polar alignment scope to center Polaris and physically align the Mount to the NCP as precisely as possible in the course of the initial set-up.
2.) Auto 2 star align per the directions with a 12.5 mm reticule eyepiece. Use a barlow as well to really hone in on the star to intially align the intial alignment stars. The question is "which" two alignment stars would be best to create the initial sky model? I suspect that these may likely be the two brightest stars picked by the computer; and, I understand that they need to be on one side of the meridian -- the question is how spread out should they be across the the half dome of the sky in order to obtain the best possible mapping?
3.) Thereafter, align with 4 calibration stars. The next obvious question is which 4 calibration stars are next best for the creation of the initial sky model? The further question is since the calibration stars are on the other side of the meridian, which ones and how spread out across that portion of the half dome of the sky should they be?
4.) Use Celestron's Polar Align function to really precisely set the polar alignment. [I note that there is talk on the forums about doing an iterative alignment between Polaris and Dubhne or other stars, but I don't know about that -- others talk about doing an interative alignment between Polaris and another stars that are 90 degrees away on the celestial equator for better polar alignment. I'm interested in this but I have never done it. The question is how to do it and which stars to use for that procedure?]
5.) Perform an Auto 2 star align again for the second time per Celestron's instructions. The question now is since the initial sky mapping has been done with the first 2 star alignment (and the 4 calibration stars); then which 2 stars should be utilized for the second 2 star alignment, i.e. should I use different ones than the original 2 stars plus the 4 calibration stars? I would suspect so, but I don't know. If so, then which subsequent stars which are different from the initial 6 stars are best utilized to create the best sky map? I would think that this issue is likely important since the choice of the second set of stars will likely more precisely model the sky's map that the computer is creating.
The question, of course, is which ones should they be, i.e. should the initial 6 alignment and calibration stars be spread across the entire half dome of the sky; and, the subsequent 6 alignment and calibration stars be chosen in a much smaller area of the sky? Or what? What is the criteria for choosing the second set of alignment stars to achieve the best possible sky mapping profile for the computer?
6.) After the second 2 star alignment, then align with 4 subsequent calibration stars.
7. Use precise GoTo with M57 in Lyra to probably Sulafat (which is what I did with the old auto 3 star alignment procedure on the old software.) If not M57 then which other DSO's or objects would best serve to best fine tune the sky mapping model that the computer is creating?
8.) Thereafter slew to a DSO object from the list in the hand control and see just how close the above alignment puts DSO in the center of the eyepiece.
9.) Figure out how to do it better.
10.) How to use the "Synch" function effectively?
11.) Once an effective and precise sky model is created as referenced above -- how to use the "hibernate" function to store such information; and, thereafter improve on the accuracy of it.
I suspect that someone has already figured this out and that they must have this information available from their personal experience in the observatory or from setting the AS CG5 GT Mount for astrophotography.
This is the type of information I am looking for; and, I suspect that many other novice users of the AS CG5 GT Mount would like to know it as well.
Thank you all in advance for any help. Feel free to PM me with any additional information, PDF files, etc. which may be too large to put into a response. Thanks again.
Best regards,
William
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WadeH237
sage
Reged: 02/24/07
Posts: 499
Loc: Snohomish, WA
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It seems like you're making it more complicated than it needs to be.
Here's what I do.
- Set the mount down roughly pointed north (I just us a compass for this) and with the latitude adjusted for your location.
- Power the mount on and enter the date/time information.
- Do a two star alignment.
- Add 4 calibration stars.
- Use the list of named stars to go to a star near the celestial equator in the south.
- Do the All Star polar alignment, accessed by hitting the <Align> key.
- Enjoy good pointing and tracking.
If you need to power down the mount, you can turn it back on, enter the date/time and do a two star alignment. If you haven't physically moved it or changed the OTA, you can skip the calibration stars and polar alignment.
To ensure accuracy, make sure that you always center the alignment and calibration stars using the up and right keys on the hand controller.
I don't have a polar alignment scope. It's completely unnecessary with this mount. The reason that I use a compass to find north above is that I usually set up before dark. If you wait until after dark, you can just look through the hole where the polar alignment scope would go and sight Polaris. This will get you plenty close for the All Star polar alignment to finish it up. Also, I don't bother with a reticule eyepiece. I just use whatever I'm going to observe with. If it's a wide field eyepiece, you can defocus the star to a doughnut to make it easier to visually center.
I hope this helps,
-Wade
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http://www.faintfuzzy.net
Stuff
Visual Stuff (shared with wife and kids, 10 & 12): Generic 6" F/8 Dob, C8-SGT, CGE-1400, Orion ED80 on a CG5-GT, Coronado PST, 6" Meade Schmidt-Newtonian, Astroscan, 12x70 Binoculars.
Imaging Stuff: Meade 8" LX200ACF with Optec TCF-S focuser on a CGE mount, SBIG ST-10XME with CFW8 and remote guide head, Astro-Tech AT66ED guide scope, Astrodon filters, QHY8PRO, DSI Pro, Canon EOS 20D, Hyperstar 3 for C8.
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Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Wade:
Thanks for the reply. I understand what you are saying.
What I am interested in ascertaining is what others, who have used this new software, have done with respect to creating the type of model of the sky as is suggested in the Celestron's literature by the 2 star alignmnet and 4 calibration stars; and, the subsequent modelling of the sky as occurs in the second alignment sequence (2 stars and 4 calibration stars).
Towards that end, I am interested in knowing which stars are selected for the first model (i.e. 2 alignment stars and 4 calibration stars); and, which stars are selected for the second model (i.e. 2 alignment stars and 4 calibration stars).
I would like to know if someone has information about how the initial alignment star pattern is spread out in the half-dome of the sky; and, I would like to know how the subsequent alignment star pattern is to be spread out in the sky in the second alignmnet pattern after the 1st alignment pattern is completed.
I believe that someone must have considered this issue heretofore; and, has aligned their scope in such a manner to achieve a very high level of accurate pointing with this software.
If anyone has done so or has information about how to do so I would most welcome their input.
William
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waassaabee
Carpal Tunnel
Reged: 11/26/07
Posts: 2702
Loc: Central California Coast
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I setup similar to Wade, though my CG5 has a Polar Scope and I would align close but not too concerned about it being dead on.
I do not use a reticule ep. I sight through my DSLR aligning on the center dot, and as Wade mentions finishing each calibration/alignment star with up and right.
I let the software pick my 2 alignment stars and 4 calibration stars (I figure it knows best).
Slew to a star for the AllStar per Celestron recommendation.
2+4 using the same stars.
Slew to first target and I can image with this alignment. No need to make it more difficult in my book.
If you want to do a drift alignment to fine tune, this is the time.
At the end of the session, slew Home, Hibernate, power down. You have to leave the mount in position for this to be effective, but next night, power on and go.
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Gary
34N 120W
-My kingdom for blue squares!-
WO Megrez 90FD/TV 0.8x FR/FF
AT8RC
mini Borg 50/Q-Guide/PHD
CGEM
Canon 350D Hap Griffin Baader mod - o.o
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WadeH237
sage
Reged: 02/24/07
Posts: 499
Loc: Snohomish, WA
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I use the 4.15 firmware with my CG-5.
The firmware selects alignment and calibration stars based on the time and site information. If you've entered the information accurately, the firmware will select the alignment stars on one side of the meridian and the calibration stars on the other. I just take the stars that the hand controller suggests in the order that it suggests them. If one of the stars happens to be behind an obstruction, I hit undo and use the next one.
I do the same thing on my CGE with 4.15 when I am imaging. The gotos put objects anywhere in the sky near the center of my CCD. In the case of the CGE, I shut down in the morning - I don't bother hibernating. Then for the next night, I just turn it on and pick Last Alignment and get the same results. Since the CGE has a real time clock, I don't even bother with the date and site information.
This works so well that I don't know what practical advantage you'd gain by choosing stars other than what it suggests.
-Wade
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http://www.faintfuzzy.net
Stuff
Visual Stuff (shared with wife and kids, 10 & 12): Generic 6" F/8 Dob, C8-SGT, CGE-1400, Orion ED80 on a CG5-GT, Coronado PST, 6" Meade Schmidt-Newtonian, Astroscan, 12x70 Binoculars.
Imaging Stuff: Meade 8" LX200ACF with Optec TCF-S focuser on a CGE mount, SBIG ST-10XME with CFW8 and remote guide head, Astro-Tech AT66ED guide scope, Astrodon filters, QHY8PRO, DSI Pro, Canon EOS 20D, Hyperstar 3 for C8.
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wsuriano
member
Reged: 11/13/07
Posts: 79
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Do you guys redo the 2-star alignment plus calibration stars after the All Star Polar Alignment following the instructions of "unsyncing" and then realigning the original alignment and calibration stars, or just skip this? Do you do it if the All Star Polar Alignement requires a large adjustment?
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Meade 8" LX90 GPS w/wedge
Meade 5000 80mm APO
Vixen 5" Newtonian
Orion 120mm f/8.3
Orion ST 80mm
Meade ETX90 PE
CGEM
CG-5 ASGT
iOptron MT
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donsinger1
sage
Reged: 10/28/07
Posts: 298
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Quote:
Do you guys redo the 2-star alignment plus calibration stars after the All Star Polar Alignment following the instructions of "unsyncing" and then realigning the original alignment and calibration stars, or just skip this? Do you do it if the All Star Polar Alignement requires a large adjustment?
With my CGEM, I unsync and resync on the original two alignment stars and add several calibration stars...takes just a few minutes and my gotos and tracking are good.
D
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Fun Stuff:)
Portland, OR
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Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Hi Guys:
Thanks for the replies. They are most helpful to me. I have sent Celestron and their technical support an e-mail message making a similar inquiry as was initially stated above. We will see what they have to say.
I am confident that whomsoever actually wrote the 4.15 software program must know which stars; in what sequence; and, in what location of the sky are best, in the course of each of the two separate 2 Star Alignment Procedures, for the purpose of creating the most accurate model of the sky.
I have not yet personally used the software as the equipment is in the southern California desert and I'm in L.A., but I will try to get out there and try it out by the next New Moon. Hopefully, by then I shall know far more about the software and how to use it than I now know.
I'm additionally interested in whether or not anyone has used the "Sync" functions; the "Hibernate" functions; the "Solar Align" functions of this software; and, with what results?
William
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waassaabee
Carpal Tunnel
Reged: 11/26/07
Posts: 2702
Loc: Central California Coast
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+1 Don & Wade!!
LA? Whereabouts? I'm north of Santa Barbara a bit.
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Gary
34N 120W
-My kingdom for blue squares!-
WO Megrez 90FD/TV 0.8x FR/FF
AT8RC
mini Borg 50/Q-Guide/PHD
CGEM
Canon 350D Hap Griffin Baader mod - o.o
My Friend Flickr
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WadeH237
sage
Reged: 02/24/07
Posts: 499
Loc: Snohomish, WA
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Quote:
Do you guys redo the 2-star alignment plus calibration stars after the All Star Polar Alignment following the instructions of "unsyncing" and then realigning the original alignment and calibration stars, or just skip this? Do you do it if the All Star Polar Alignement requires a large adjustment?
I don't.
I've found that as long as I'm careful about centering the star during All Star alignment, I haven't needed to re-align. It's a good idea to un-sync, though.
As my rule of thumb, I do a two star alignment (or just update the two alignment stars while running) if something has happened to change alignment, like the mount powered off or a clutch slipped, etc.
The purpose of the calibration stars is to give the mount a model to correct for orthogonality issues (this is where the mount's RA axis and the OTA may not be in perfect alignment.) The result of this calibration is stored in the hand controller's non-volatile memory. As such, I only do the calibration stars when I've just put on the OTA and this has worked well for me.
-Wade
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http://www.faintfuzzy.net
Stuff
Visual Stuff (shared with wife and kids, 10 & 12): Generic 6" F/8 Dob, C8-SGT, CGE-1400, Orion ED80 on a CG5-GT, Coronado PST, 6" Meade Schmidt-Newtonian, Astroscan, 12x70 Binoculars.
Imaging Stuff: Meade 8" LX200ACF with Optec TCF-S focuser on a CGE mount, SBIG ST-10XME with CFW8 and remote guide head, Astro-Tech AT66ED guide scope, Astrodon filters, QHY8PRO, DSI Pro, Canon EOS 20D, Hyperstar 3 for C8.
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Patrick
Postmaster
Reged: 05/16/03
Posts: 7808
Loc: Franklin, Ohio
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Hi William,
Quote:
1.) Polar Align it as accurately as possible in the intial set-up with bore sighting Polaris through the Mount's hole; and, use the polar alignment scope to center Polaris and physically align the Mount to the NCP as precisely as possible in the course of the initial set-up.
Since you will be doing a precise polar alignment later on in your alignment procedure, doing a precise polar alignment through a polar scope at the beginning of the process may not be necessary. I've found doing a rough polar alignment through the polar axis hole, plus making sure the mount is level to be all that is required. In fact the CGEM manual (I'm referring to the manual for the CGEM since it's up to date with the latest firmware) essentially says the same thing on pages 14 and 15 where it describes the process for 'Adjusting the Mount'. The manual doesn't mention leveling the mount, but I suspect it assumes that it is level.
Quote:
2.) Auto 2 star align per the directions with a 12.5 mm reticule eyepiece. Use a barlow as well to really hone in on the star to intially align the intial alignment stars.
Which magnification you use may be more of a function of the focal length of your telescope. If you have an SCT, a 12.5mm reticle may be just fine. If a shorter f/l scope, then perhaps a 5mm reticle or a barlow would be better. One important thing to do whatever the focal length of your reticle eyepiece is to do the final movements with the right and up arrow keys to always keep the gear backlash out of the equation.
Quote:
2.) The question is "which" two alignment stars would be best to create the initial sky model? I suspect that these may likely be the two brightest stars picked by the computer; and, I understand that they need to be on one side of the meridian -- the question is how spread out should they be across the the half dome of the sky in order to obtain the best possible mapping?
Are you looking for specific names? If so, that totally depends on when you're observing, of course. But, I don't think that's what you mean. I think you mean how does Celestron decide which stars to use for the first and second alignment stars. I don't know except they're in the western hemisphere, and they are usually a star in the southern and then northern sky, or vice-versa. So, I think that means they're spread out as far as possible to get the largest angular dimension that it can...which makes total sense.
At my own observing site, I have a lot of trees and the house blocking a substantial part of the sky, so I have to use the up and down arrow keys to select the stars that I can see. I try to keep them as far a part as possible.
One other thing to consider when picking the alignment stars it to not pick a star too close to the horizon because of atmospheric refraction. The star may not really be exactly where you think it is.
Quote:
3.) Thereafter, align with 4 calibration stars.
The CGEM manual, page 19, says "it
is recommended that you add as many as three calibration stars for optimal
point accuracy". Personally, I've found that adding two calibration stars provides excellent goto accuracy.
Quote:
The next obvious question is which 4 calibration stars are next best for the creation of the initial sky model?
Also from the CGEM manual, page 19: "Calibration stars that are near the equator offer the best results than stars near the poles."
Quote:
4.) Use Celestron's Polar Align function to really precisely set the polar alignment. [I note that there is talk on the forums about doing an iterative alignment between Polaris and Dubhne or other stars, but I don't know about that -- others talk about doing an interative alignment between Polaris and another stars that are 90 degrees away on the celestial equator for better polar alignment. I'm interested in this but I have never done it. The question is how to do it and which stars to use for that procedure?]
This is a technique that has been employed to avoid doing a drift alignment. I think the new Celestron polar alignment routine will relegate the technique to the back burner.
Quote:
5.) Perform an Auto 2 star align again for the second time per Celestron's instructions...should I use different ones than the original 2 stars plus the 4 calibration stars? I would suspect so, but I don't know.
I don't see any reason why you couldn't reuse the original alignment stars. If the alignment was thrown off by the polar alignment routine, then you're just telling the computer where the stars are really located again. By the way, you can sync and un-sync at any time. If a goto is off a little, I will routinely put the object in the center of the fov and sync on it.
Quote:
6.) After the second 2 star alignment, then align with 4 subsequent calibration stars.
I don't think you will need to add the calibration stars. Goto an object you'd like to see, and if it's not centered in the fov (it should be close), then center it and sync on it.
Patrick
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10" f/6 Truss Tube Newtonian
Celestron C6S-GT SCT
AT66ED Refractor
Oberwerk Ultra 15x70 Binocular
475B Geared Tripod & 501HDV Head
Celestron Regal 8x42 Binocular
Canon XSi; Meade DSI;SPC900-NC
Vixen GP2 Photo Guider Mount
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bdjeep
sage
Reged: 01/29/07
Posts: 440
Loc: Bolton, MA
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Have you tried the "Select Alignment Stars" utility at Nexstarsite.com? This should tell you which stars are good choices for your initial alignment given the time & location. However, I've never had a problem with the choices from the hand controller.
Are you a visual observer, or are you going to be imaging? If visual, I think you are making the process entirely too complicated.
Here is my process for visual use:
Just plop the scope down, level the tripod (approximately), align index marks, adjust alt-az until you get Polaris in the finder and then in the main scope. Turn on the mount, enter date/time, etc. Pop in a 25mm eyepiece, align on 2 stars (hand controller choice is usually fine.) Calibrate on 2 more. Observe and enjoy. This is simple, easy, and almost never fails to put objects in the FOV of my 25mm Plossl.
When I'm doing some planetary imaging, I'll be a little more careful with the initial polar align, followed by the new All Star polar alignment. Sometimes I'll add a couple of extra calibration stars if I'm feeling particularly motivated.
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Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Quote:
Have you tried the "Select Alignment Stars" utility at Nexstarsite.com? This should tell you which stars are good choices for your initial alignment given the time & location."
I did previously before I posted the original e-mail message -- but I could not open the program. I'll try it again today.
I would like to create an alignment map to use along the parameters which Celestron has used in their software program. I am very interested in having this type of an "alignment map" for the Spring/Summer stars; and, a second one for the Autumn/Winter stars.
I really want to understand exactly how this new software works and how to effectively use it on the AS CG5 GT mount. I was quite impressed with the precision of the old software with the old auto 3 star align when it was carefully polar aligned; and, thereafter carefully aligned with the 3 object stars under the old software.
After reading the literature on the new 4.15 and 4.16 software I am even more persuaded that the capabilities of the new software far supercede the old software.
I am fully persuaded that once an appropriate mapping of the sky is carefully modeled by the computer (likely along the lines some of you have suggested)with 12 reference stars for the computer to use in the process -- then the pointing is likely to be highly accurate -- which is necessarily important for a novice like me to use in order to locate 13th - 15th magnitude objects, i.e. the Quasar 3C273; and, other such distant, dim Deep Space Objects.
I did send Celestron's tech support a similar e-mail message requesting further details on this same sort of stuff. I'll let you know their response.
William
Edited by Charlie Hein (05/05/09 07:19 AM)
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Patrick
Postmaster
Reged: 05/16/03
Posts: 7808
Loc: Franklin, Ohio
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Quote:
then the pointing is likely to be highly accurate -- which is necessarily important for a novice like me to use in order to locate 13th - 15th magnitude objects, i.e. the Quasar 3C273; and, other such distant, dim Deep Space Objects.
Have you seen the hand controller's "precise goto" feature? It's designed to do exactly what you're describing.
Patrick
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10" f/6 Truss Tube Newtonian
Celestron C6S-GT SCT
AT66ED Refractor
Oberwerk Ultra 15x70 Binocular
475B Geared Tripod & 501HDV Head
Celestron Regal 8x42 Binocular
Canon XSi; Meade DSI;SPC900-NC
Vixen GP2 Photo Guider Mount
My Astronomy Pages
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Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Patrick:
Yes. I've used it with the old software (4.12, I think it was).
Don Pensack sent me an e-mail message in response to my questions. I'll summarize his thoughtful responses and post them soon as I am able to do so as I think that you and others may find those thoughts as useful as I have.
Best regards,
William
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Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Patrick:
Please be advised that I read somewhere in Celestron's literature that Celestron does, in fact, recommend for their 2 Star Alignment Procedure: 2 Alignment Stars and 4 subsequent Calibration Stars. If I remember correctly I think that this procedure was specific to the AS CG5 GT Mount. I will check on that issue and get back with you on it since I know that you use that mount as I do.
Here is a summary of what Don advised me when he responded to my rather poorly phrased questions on this issue which I have put in a Q and A format:
Question: From looking at Celestron's literature, it seems that the intial 2 alignment stars are all on one side of the meridian and that they should be as widely spread apart as possible. The question is which stars should one use on the East and which on the West for the initial 2 star alignment? I would assume that one would select the ones that the computer picks, but that may not be the case; and, it well may depend upon what calibration stars are selected as well as where the initial stars are located in the sky, i.e. lower half of the sky dome or upper half of the sky dome.
Answer: "Accuracy is highest, from what little knowledge of cartography I possess, when one star is south of the equator, one star is north (both east), and one star is near the equator (in the west), though as long as the triangle is large, calculations should pick up cone error. Do not use any star near the pole as smaller and smaller movements of the mount result in larger and larger errors."
Question: As for the 4 subsequent calibration stars, the same question applies --which ones and where should they be located on the opposite side of the meridian for the creation of the sky model for purposes of the best alignment?
Answer: "Using alignment stars near the field of primary target results in the greatest accuracy, which is the raison d'être of Precise GoTo."
Question: "This is relevant because in trying to understand how the computer program algorithms work it may be that the alignment stars and calibration stars selected in the intital 2 star alignment (and subsequent 4 calibration stars) need to be selected in the bottom half of the sky's half dome (i.e. in the area from the horizon to say 45 degrees up from the horizon) or would they need to be selected in the upper half of the sky's half dome (i.e. say 45 degrees up to the zenith).
Answer: "Stars near the horizon suffer from refraction and choosing them will cause errors. Never chhose an alignment star closer to the horizon than 30 degrees."
Question: If the computer is creating a model of the sky I think that this may be important to know because a more accurate model would obviously be created depending upon how the program's algorithms work. This is important because if the next step is to do the computer's polar alignment [which is based upon the initial 2 star alignment (and 4 calibration stars)]; then after the polar alignment, a second 2 star alignment is required (with another 4 calibration stars).
> The issue for purposes of the creation of an extremely accurate sky model in the computer becomes which stars are now to be chosen in the second 2 star alignment (and 4 calibration stars)?
Answer: "They can be the same stars. The accuracy will depend on accurate centering of the stars. You don't need to worry about the speed with which you choose the stars, either, as the clock is running while you select. Your confirmation of the location of the second star confirms the "twist" of the celestial globe relative to the first star."
Question: If, in the initial alignment the stars in the lower half of the sky's half dome are selected (i.e. stars from the horizon level to say 45 degrees up); then in the second 2 star alignment procedure, should stars in the upper half of the sky's half dome be selected (i.e. stars from 45 degrees to the zenith)?
> The central question is which stars of the 12 stars which are used in the alignment process (i.e. the 4 alignment stars and 8 calibration stars utilized in 2 separate alignment procedures) should be used; and, in what sequence should they be chosen, in order to create the best model of the sky for the Celestron 4.15 and 4.16 software program to create the most effective model of the sky.
Answer: "I'm not sure it's real critical because I've used the 3 stars chosen by the mount, I've chosen them myself, I've had them close together, and far apart, and the pointing accuracy has been good in every case."
Question: I am sure that somebody knows the answer to this question, but I don't know who. I checked Mike Swanson's website and could not find the answer there. I googled it without success so far. I've posted the question on CN and the last time I looked I there was no response which answered the question. Celestron's software engineers should know or at least the person who wrote the program should know. If all else fails, I plan on writing to Celestron to try to ascertain this information.
Answer: "The program was written by Synta Corporation, so I hope you speak Chinese."
Question: On Mike Swanson's website there is a computer program called "Best Pairs" which was written for the Meade LX 200 fork mount which selects the best pairing of stars for the Meade autostar program. Something similar must exist for Celestron.
> Moreover, since other computer programs interface with Celestron's 4.15 software [such as Starry Night Pro and The Sky] there must be something out there which identifies which 12 stars and in what sequence best align the telescope's mount.
Answer: "The accuracy should be highest with the greatest separation so long as no star is below 30 degrees (meaning alignment stars could be as much as 120 degrees apart)."
I like Don's reasons as they make sense to me. When I have some time this coming week I would like to create an "alignment map" of the night sky to be used in the early evening (dusk and thereafter) to use to model the sky according to the parameters that Don has set forth plotting out the 4 Alignment Stars and the 8 subsequent calibration stars.
Maybe someone who has more free time available and a similar interest may beat me to the punch on this; and, if so, I would be interested as there is no need to re-invent the wheel. On the other hand, others may well have thought this matter through along a similar path and have some input to offer as well. It certainly would be welcomed.
Finally, as previously stated I am really interested in learning how to fully use this new software, including all of its functions such as "Solar Align;" "Polar Align;" "Precise GoTo;" "Synch Function;" the "Hibernate Function;" and, the other functions.
Best regards,
William
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Patrick
Postmaster
Reged: 05/16/03
Posts: 7808
Loc: Franklin, Ohio
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William,
It's nice that Don is confirming most everything I've said. The one thing I didn't know was that the software was developed in China. Regarding the algorithms, I think you will find that they are highly proprietary, meaning 'trade secrets'. I don't know if you recall the 'goto wars' that Meade and Celestron fought out in court several years ago, but the bottom line was that Celestron had to redesign a number of their products, including their software. Because of that, I'll think it's highly unlikely you'll get the depth of information that I think you're looking for.
Quote:
model the sky according to the parameters that Don has set forth plotting out the 4 Alignment Stars and the 8 subsequent calibration stars.
If I read Don's responsed correctly, he did not advocate using 4 alignment stars and 8 calibration stars, rather you quote him as saying, "I'm not sure it's real critical because I've used the 3 stars chosen by the mount, I've chosen them myself, I've had them close together, and far apart, and the pointing accuracy has been good in every case." I read that to be a total of three stars. That mimics my experience as well, except I generally use a total of 4 stars (2 alignment and 2 calibration stars), as recommended in the CG5-GT manual.
I'm pretty sure Celestron has designed their new firmware upgrade to make it easier to get a good alignment, not harder. I can't find anywhere that Celestron makes the statement to add 4 calibration stars, and in fact, the CG5GT manual recommends only 2 calibration stars be added for 'optimal' accuracy (page 19 in the CG-5GT manual). If you can find the other recommendation, please let me know.
One practical thing you might try is to play around with the mount during the daytime. You could simulate the time, date and location of your planned observing trip and go through the alignment routine to see which stars it picks and in which order. If you have a planetarium program like the Sky 6, you could then plot the stars to identify their location and create the mapping program you're interested in seeing for those times and dates. With the planetarium program you can also see what the star elevations are and if there are any other good choices for alignment stars that the hand controller didn't pick. For reference you can use the Nextstar Resource site to obtain a list of all the named stars that Nexstar uses for it's alignment stars.
Regards,
Patrick
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Chris Rowland
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I don't know where these rumours come from.
The AS-GT software is NOT developed in China. I know the developer and he isn't Chinese.
Synta do separate software for their mounts, I don't know where that's developed.
As for selecting alignment stars, my suggestion is not to get too hung up with selecting precisely the "correct" stars, a pair of stars that are reasonably well separated, by which I mean more than 40 degrees and less than 140 degrees, will do.
More importantly IMO is to do a good job of centring the stars you are using. Use a reticle EP.
Similarly for the calibration stars, choose reasonably well separated stars. If the alignment is going well then by the second or third star the alignment will be good enough that the next star is already almost centred.
There aren't any magic stars, the "secret", if there is one, is to do a good and consistent job of centring the ones you are using.
Chris
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Patrick
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Quote:
The AS-GT software is NOT developed in China. I know the developer and he isn't Chinese.
Chris,
That's good to know. Thanks for clarifying who developed the software. I also agree with you that by the third or fourth alignment star the goto's are pretty close to being dead on. After that, if more precision is required, then the 'precise goto' feature can be employed, but quite frankly, I've never had to resort to that. I've even imaged faint objects without being able to see them in the eyepiece and only knew they were there after taking a photo.
Patrick
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Tarzanrock
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Reged: 12/07/08
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Hi Patrick:
It seems that it is my mistake about the four (4) calibration stars. I must have gotten that wrong from all that I've been reading trying to figure this out.
I again checked the Celestron website as well as Swanson's and the Celestron Manuals -- they appear to recommend 3 calibration stars. I believe that they do recommend a first 2 star alignment with 3 calibration stars; then their polar alignment process; and, then a subsequent 2 star alignment process with 2 alignment stars and at least 3 calibration stars.
I have some planetarium software (The Sky version 6.2 or something like that and Starry Night Pro); and, I fooled around with it this afternoon using the parameters that Don recommended.
I'm interested in figuring out the alignment mapping for the New Moon in May around May 20th or so because that is likely the next time in which I may be able to get out to the desert to play with the telescope.
Given the 30 degree upwards parameter that Don advocates -- it looks as though the easiest and brightest stars on the East are: Arcturus; Spica; Vindemiatrix; Alakid; Mizar/Alcor; Izar; and, Murphid.
On the West it appears that the easiest and brightest stars are: Pollux; Castor; Procyon; [Capella (a little below the 30 degree line)]; Alphad; Regulus; Algieba; and, Denebola.
When I have some more time, I will set down with a more detailed map and try to figure out which alignment and which calibration stars have the greatest distance in terms of what you and Don have been discussing with me.
Once I determine which 2 intial alignment stars and which calibration stars within those parameters; I will then consider a second set. I am most interested to know how well the mount will perform once this stuff is figured out.
I have downloaded the CGEM Manual that you have discussed and am in the process of studying it.
At page 19 it states in italics: "Calibration stars that are near the equator offer the best results than the stars near the poles." Aside from the grammatical error in the sentence structure, I am curious what Celestron actually means by the use of the term "equator" because it is vague and ambiguous as it is used in this sentence in their manual. In figure 3-3 on page 20 Celestron defines what they mean by "The Meridian" but they do not define what they mean by their use of the word "equator." Moreover, Celestron's "May - June Sky" Map at about p. 66 has the "ECLIPTIC" drawn onto it.
There are two circles drawn near the edge of that map. I understand the the exterior circle is the map's boundary, but I do not know the significance of the interior circle next to the boundary demarcation. The question is whether the inside circle is supposed to represent the "equator" or is it merely the horizon line? It's pretty vague. On that map Celestron's alignment stars of Capella, Castor, Pollux, Regulus are clearly drawn near that line.
By the way, Celestron still has not responded to the e-mail message that I sent to them. I think that they are giving it due consideration and I anticipate a positive response.
Lastly, have you calibrated your Mount using the Calibrate Mount feature under the utility features as set forth on pages 28 and 29 of the CGEM manual? I am interested in the R.A. Switch Feature (p. 29) and I would assume that you would be interested in the Goto Calibration feature at page 29 since you do astrophotography.
William
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Tarzanrock
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Reged: 12/07/08
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Hi Chris:
I appreciate your comments very much. It is irrelevant to me who developed the software. I'm actually very pleased that it was developed here.
What I am interested in understanding is which stars (2 alignment stars) and which calibration stars work well for obtaining a very precise alignment.
Last year, I used the old software (version 3 something) with my mount; and, it was quite precise in its pointing using the old auto 3 star align system.
From the literature, I am convinced that the new software is a huge advance; and, I further realize that if I am to effectively use the mount to its capabilities, I need to learn how to use this software as effectively as possible.
Thanks for the information about the 40 degree and 140 degree separation in choosing the alignment stars. It is most useful.
For me, the obvious follow-up question concerns the calibration stars -- i.e. once the intial 2 alignment stars are selected on the East; where approximately should the first calibration star be selected on the opposite side of the meridian from the two intital alignment stars?
The next question is where should the second calibration star be selected? Should it be on the same side of the meridian as the 1st calibration star (i.e. on the West [the opposite side of the initial 2 alignment stars]) or is it permissible to choose one on the East?
Where should the third calibration star be selected after the second calibration star is entered into the computer's memory?
[I realize that Don thinks that the calibration stars should be in the immediate area of the sky that you want to target, but what if you plan on viewing the whole sky that night?]
Moreover, after the polar alignment routine is completed; and, the second 2 star alignment process is begun -- where should these alignment stars be selected?
[I know that Don advises that the same ones can be used but I wonder whether or not a better alignment could be achieved by using different stars to refine the model of the sky that is being created in the computer?]
If so, (and I suspect so) I would like to know generally the location and sequence of these alignment and calibration stars.
Perhaps your friend who developed the software could advise me or tell you and you could advise me. I'd like to know the answer to these questions.
I would suspect that there are about 8 to 12 stars out there upwards of and above the 30 degree line; and, that these stars are located broadly across the night sky which if selected in a certain sequence and thereafter properly centered and entered into the computer -- then the Mount would be extremely accurate in precision pointing.
I am certain that the new software, at a minimum, is more than capable of that function.
I would appreciate it if you would kindly pass my request onto your friend, the developer, as I am interested in learning this as well as how to use the other features of the software as well -- such as the precise goto; sync feature; polar align; RA switch; goto calibration; hibernate; and, home position.
It is clear to me that each and all of the above functions are most dependent upon the accuracy of the initial 2 star alignment with the 3 calibration stars.
Chris, thanks for taking the time to consider this. I don't think that I am the only person who has these questions.
William
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Patrick
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Quote:
I am curious what Celestron actually means by the use of the term "equator" because it is vague and ambiguous as it is used in this sentence in their manual.
The term 'equator' used by Celestron refers to the Celestial Equator. Since the RA axis of the mount is pointing towards the pole, pointing the scope towards pole stars results in a very small angular distance for the computer to use to calculate the cone error of the axis.
Using a star at the celestial equator puts the alignment star closer to 90° more or less (depending on your latitude) off of the mount's RA axis and therefore more precision in calculating the axis cone error. Keep in mind that it's the cone error of the mount's RA axis that the software is trying to compensate for.
HERE's a List of constellations that fall on the celestial equator. It also gives a much better explanation of the celestial equator.
Patrick
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Chris Rowland
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Reged: 02/28/05
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My criteria for selecting alignment stars are:
- Visble - I usually observe close to the house so all of the Northern sky and most of the Eastern sky isn't visible.
- Not too high so I don't have to bend too much to see through the finder, I usually go for something in the 25 to 45 degree range.
- Bright - so it's easily visible with a red dot finder.
I do this for the alignment stars and the first calibration star; after that it's likely that the stars will be in the scope field so I'd try one high and one low.
Now, at the end of twilight, I'd probably start with Regulus and probably Castor or Pollux as the second alignment star, then Arcturus for the first calibration star.
Something in Ursa Major will do for a high star and maybe Spica for a low one.
I'm in the UK, if I was further South then they will be different.
I really wouldn't get hung up on selecting the perfect set of stars, just stars that are reasonably well separated and that cover the area in which you plan to observe.
With the new AllStar polar alignment I'd use Arcturus.
There's no need to completely redo the alignemnt after polar aligning but I'd just use the same stars and refresh their positions using the replace alignment stars option.
The mount correction parameters are remembered so if you use the same setup every time you may find that the calibration star setup doesn't always need to be repeated.
Chris
Edited by Chris Rowland (05/05/09 07:16 AM)
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bdjeep
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Reged: 01/29/07
Posts: 440
Loc: Bolton, MA
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Quote:
With the new AllStar polar alignment I'd use Arcturus.
There's no need to completely redo the alignemnt after polar aligning but I'd just use the same stars and refresh their positions using the replace alignment stars option.
This is a good point and a time saver. If you are using the All Star polar alignment (and you really should, it's quite nice), you don't need to bother with another alignment/calibration with different stars.
You really don't need to over analyze which initial alignment stars you choose. I use Chris' "lazy man" criteria as well (visible, bright, comfortable viewing angle). I think you'll find that when you really start using this mount, the pointing accuracy is quite good. Bright objects, faint objects, etc. all land within the FOV of a low power eyepiece. If you are still not sure, use the precise goto feature and it will be spot on every time.
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bebert
sage
Reged: 07/21/08
Posts: 247
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Don't over analyze this. Just use the tips and methods that have been posted here and enjoy your precise gotos. Ever since 'all star' came out my set up time has decreased considerably. No more drift aligning for me.
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Celestron C8
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Tarzanrock
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Reged: 12/07/08
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Quote:
Using a star at the celestial equator puts the alignment star closer to 90° more or less (depending on your latitude) off of the mount's RA axis and therefore more precision in calculating the axis cone error. Keep in mind that it's the cone error of the mount's RA axis that the software is trying to compensate for.
Patrick: I had some time last night so I played with a star atlas. It seems to me that in following the advice of all on this board (as well as that of Don Pensack) that if, for the New Moon weekend of 5/22/09, I align the AS CG5 GT Mount as follows:
1.) Initial 2 star Alignment -- choosing Spica, Arcturus or Vega in the Eastern sky to broadly spread out the triangular alignment pattern out across the sky.
2.) Choosing either Pollux or Castor or Procyon as the first calibration star in the West.
This should give a well spread out triangular pattern across the night sky in accordance with the parameters set forth by yourself; Don; and, Chris Rowland. However, I do think that Vega and Procyon may likely be too far below the 30 degree line that Don has suggested. What are your thoughts on that issue?
3.) The next question becomes what about the 2 subsequent calibration stars which follow in the alignment procedure? Don believes that they should be chosen from the constellation that one is planning on observing so as to achieve greater accuracy. I'm not sure about that, but assuming so; and, if one wanted to observe in Leo or Virgo, my question would be whether anyone has any idea as to approximately how far spread apart these two subsequent calibration stars should be in the subject constellation?
For example, assuming Leo: a.) should the calibration stars be broadly spread apart such as: choosing Denebola and Regulus or Rasalas; or, should they be narrowly spread apart such as choosing: Denebola and Zosma and Chertan (Chort)?
The same questions would follow if Virgo constellation were selected for the 2 additional calibration stars -- should they be broadly selected across the entire breath of the Virgo constellation or should their selection be more narrowly construed?
If Don is correct, it seems to me that it should be narrowly construed, but I do not know the answer to the question. I would like to know the answer.
I think that it is relevant because assuming that you want to observe the Virgo galaxy clusters you may want to try to fine tune the initial alignment with the calibration stars in that specific area as Don has suggested by selecting the calibration stars closest to that area. I suspect that this is the case but, I do not know that it is, in fact, true. I would like to know the answer to this question.
Unfortunately, today Celestron's tech support replied to my question with what is essentially a non-answer as they gave a non-specific, generalized reply that is not helpful.
At the present time I am currently thinking that I will probably align it in this fashion when I next get the chance to do so. On the other hand, I am sure that someone with far more experience than I has far better ideas than I as to how to align this mount with this software; and, I most welcome their input.
4.) The other question is that if the 2 calibration stars are not chosen within a specific constellation (such as Virgo or Leo) -- where would these calibration stars best be chosen from, i.e. which other stars and which other constellations? Looking at a map, in the West, without Virgo or Leo, that leaves pretty much Leo Minor, Ursa Major and Lynx constelaltions. What are your thoughts on that? Should the two calibration stars be broadly picked across the span of several constellations or not? If so, which ones and which stars work best from your experience?
That brings up the next point -- Polar Alignment and the All Star Alignment Process. The CGEM Manual, page 37 states: "For best results choose a polar alignment star that is high in the sky and near the Meridian. Try to avoid stars that are close to the west/east horizon, directly overhead or too near the celestial pole."
In looking at the star atlas the best candidates in terms of proximity to the Meridian appear to be: Mizar and Alioth in Ursa Major; Vindemiatrix and Auva in Virgo. Stars which are more widely spread out from the Meridian appear to be: Thuban and Dubhe in the North; and, Arcturus and Denebola in the South. I would assume that Kochab is likely too close to Polaris to be useful.
A. What have you (and others) done in your choice of the selection of the Polar Alignment Star?
B. After you Polar Align the Mount, how do you perform the second 2 Star Alignment?
Do you use the same stars as were used in the initial 2 star alignment or do you change the stars?
If you do change the stars for the second 2 star alignment, do you change the side of the Meridian to the opposite side in order to select the alignment stars the second 2 alignment stars from? Celestron ducked this question as well. Would you achieve a better sky model for alignment of the whole sky if you did do so?
William
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DaveJ
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Reged: 01/07/05
Posts: 332
Loc: NE Ohio
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William,
You're working far too hard at this. Take the first two alignment stars it suggests and don't fret about it. Chances are excellent that it will pick two stars WEST of your meridian - mine always does. Following that, add three or four calibration stars which it will pick EAST of your meridian. After that, Goto a named star near the intersection of your meridian and the Celestial Equator ("Celestial Equator" means DEC=zero) and then do the AllStar Polar Align routine. This works perfectly EVERY TIME for me and not only centers every object no matter where in the sky it is, but also polar aligns the mount so no drift at all is seen. Celestron is to be congratulated on this software - and I have in a call to them.
You can fret and demand certain alignment and calibration stars, but for what? Take the ones the mount suggests and everything will be as good as it gets.
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Dave Jessie
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waassaabee
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Trust the force William....
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Gary
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Tarzanrock
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Reged: 12/07/08
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Dave:
That is interesting because it was my understanding from the literature that the software would pick the initial two alignment stars from the "East" side of the Meridian, but you say it picks the initial alignment stars on the "West" side.
Other than that I do understand what you are saying; and, notwithstanding that statement, I still do wish to learn how this software works and which star alignment patterns do work best with it for precision alignment.
By the way, which stars do you use when you get the ultra accurate "perfect" alignment that you have described?
William
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Tarzanrock
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Reged: 12/07/08
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Gary:
I'm not sure which "force" it is that I should be trusting (since there are many "forces") nor am I certain that I should trust any of them.
William
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Tarzanrock
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Reged: 12/07/08
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Gary:
It's scepticism and animal faith -- as George Santayana would put it.
William
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CounterWeight
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I had one for about a week and sold it, not because of the software though - really I found it a good value for what it is/does, and the all star I really do like. So I loaded it my CGE. I have to admit that I miss aligning on Polaris but I'll get over it. I think what you are doing makes 'more' sense when you read the old literature about Polaris and celestial pole and etc... what polar align is about and what it's supposed to do for you.
I also applaud Celestron for the new routine, it's only possible due to 'high tech' and etc.
In many ways it is very much the same though?
- make sure mount is reasonably level and poining reasonable north
- center 2 stars on mounts west meridian sky
- use calib stars on mounts east meridian
* align on a star of known location (used to be Polaris, now can be any star you can see in a mount neutral position) 'mechanically'. It's simple and I think elegant solution as the star field essentially is unchanging. I think it makes sense to say now try to find a star at roughly a right angle to Polaris?
-go back and re-calibrate to compensate eletronically for the physical/mechanical adjustment made. Can re-do cone as well.
So to me it seems very much the same in all except the star used to polar align.
Wish it gave a choice between the Polaris and all star routines. Also wish (and this a carry over from previous method) it went (newer - zero out sync and go directly into a new align) (older - go directly to new aligment)
In both cases it's possible to slew to something without new align. Just your object will be off center proportional to the physical adjustment made...
The software seems to pick enough stars that I can get to in my odball of a sky map from my backyard (and can 6 or 9 on pad to change if desired... oops Duhbe is still behind my neighbors house, what's next choice?) the one I think is interesting is it chooses Mizar a lot (bright double) but hey, when i'm done it's really pretty amazing - cant see the Crab(M1) but when I image it is center fov  I find that pretty impressive
I align in a very odd wedge/rectangle shape my house blocks E partially, neighbors house blocks West a lot. So I often cant use the first choice stars, but even using alternatives, it picks the bright ones, and it's easy and it works - in my much less than ideal situation.
I think Meade and Losmandy have additive pointing models that you can really get into if desired, add stars and improve on as you go - but this isn't that.
I think this "all-star" polar align is a pretty reliable 1-2-3- go! setup and using the choices given works pretty well. Add the tool-free polar adjustmant (as touted on the newer CGEM and CGE-pro) and it's even more easy.
You mention optimal. To me optimal means doing what it says in the crazy world we amatures try to make it work in, so it needs to work in a lot of less than ideal alignment situations. The fact that it polar aligns without the pole is pretty optimal if you cant see it
A method of finding the best might be a bit difficut but not impossible. Use different stars each time (each night when starting out) and leave the reticle ep in, slew to different targets and record the error. The more you do it the more noise would be removed from slight differences in align night to night. After a month or two graph the results into a polar plot (color coded or something) and then see if there is a dominant 'minimal' vector in certain choices of align stars?. I think that would give a best align for your mount in your place in your sky with your scope, etc... maybe? If the vector spread is all over the circle radially and about the same magnitude in all directions then you'll know pretty well it doesn't matter.
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waassaabee
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William, You can select East or West your alignment stars. I use West so that my calibration stars will be in the East where I normally image.
I really think if you would go out one night and try to let the mount do it's thing, you'd realize how accurate and simple it really is.
Or you can anguish over it and ruin a perfectly peaceful evening under the stars.
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Gary
34N 120W
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Patrick
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Reged: 05/16/03
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Quote:
1.) Initial 2 star Alignment -- choosing Spica, Arcturus or Vega in the Eastern sky
My mount always goes to the western sky first, then east for the calibration stars.
Quote:
The next question becomes what about the 2 subsequent calibration stars which follow in the alignment procedure? Don believes that they should be chosen from the constellation that one is planning on observing so as to achieve greater accuracy.
I always try to end up with the last star being the one I'll use to do the all-sky polar alignment. Right now, I'm using Denebola. I was using Regulus, but it's moving into the western sky now.
Quote:
Don believes that they should be chosen from the constellation that one is planning on observing so as to achieve greater accuracy.
What I normally do after a goto alignment and polar alignment, is to goto an object I want to view. If it's not dead center in the eyepiece, I place it there and then do a 'sync' on the object. That's somewhat equivalent to realigning. It's giving the computer more data to work with.
Quote:
A. What have you (and others) done in your choice of the selection of the Polar Alignment Star?
Right now, I'm using Denebola. It's in the eastern half of the sky and in the south. I was using Regulus, but not it's too far west and the scope will do a meridian flip to get to it.
Quote:
B. After you Polar Align the Mount, how do you perform the second 2 Star Alignment?
I haven't been. I will slew to an named star near the area I will be imaging, center it in the eyepiece and sync on it. It may be better to do a second star alignment, but I'm not sure. If I would do a second 2 star alignment, I would use the same stars I used for the first one.
Patrick
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10" f/6 Truss Tube Newtonian
Celestron C6S-GT SCT
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freestar8n
sage
Reged: 10/12/07
Posts: 299
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Hi-
This is an interesting thread. I think a lot of the comments about just being cool about things are on target. I'll summarize my own impressions:
1) A 2+3 or 2+4 alignment should be pretty insensitive the the star choices. They must be on opposite sides of the meridian, though.
2) You can use 2 stars in the east or west when you start the alignment. This is one obscure thing about the process: press MENU to toggle between starting in the E or W.
3) If you do a careful alignment with crosshairs on two stars, they could be castor and pollux and it would work fine, as long as you also add calibration stars. The stuff about wide stars, etc., probably doesn't apply here.
4) Goto accuracy should be pretty independent of polar alignment and level. If you are setting up quickly for visual work - you don't even need to polar align. The alignment will only affect how long things stay in the view - but goto accuracy should be very good.
5) If you do want to finesse the accuracy, it will tend to be more accurate around the align/calib stars. So if you are viewing a section of the sky, have some of those stars near it. If you are bouncing all over the sky, use stars all over.
6) When you do a calibration, like 2+3 or 2+4, it does calibrate the mount/ota itself, so the next time you just do a 2-star alignment, the goto accuracy should be better even if you moved the mount. But adding calib stars will help if you want/need to.
7) As always, finish motion with the up/right arrows. Make sure the mount is tight, including the tripod bolts, etc., so nothing flexes.
8) I don't think there is anything special about the stars suggested by the handcontrol. What I do is select stars moving outward from the pole for calibration. That ends up being faster because just after the meridian flip you go to a star on the other side near the pole, and then move down. I stagger things a bit in E/W and N/S. I also like to choose stars near each other alphabetically so I don't have to scroll much - but that is just for lazy amusement.
9) I forget if the cg5 has index switches like my cge. If it doesn't, make sure the indexes are lined up carefully. But I'm not clear about how they work on this mount.
Have fun-
Frank
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rmollise
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Reged: 07/06/07
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Quote:
Hi-
9) I forget if the cg5 has index switches like my cge. If it doesn't, make sure the indexes are lined up carefully. But I'm not clear about how they work on this mount.
Have fun-
Frank
No index switches...instead you line up on two marks that ensure you start from the same RA/Dec positions each time.
As for the original poster? Just accept the stars the HC gives you and move on. The single exception? If the mount offers an alignment star lower than 30 degrees, it's probably a good idea to push "undo" and pick another, higher one.
--------------------
Uncle Rod
Rod's New Book:
Choosing and Using a New CAT
Available now!
Edited by rmollise (05/06/09 09:37 AM)
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freestar8n
sage
Reged: 10/12/07
Posts: 299
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Hi-
Quote:
No index switches...instead you line up on two marks that ensure you start from the same RA/Dec positions each time.
In this case, I would very carefully align the dec. index mark each time. The RA is less critical. If you don't line things up the same as for prior usage, then the calibration you did previously won't be as accurate this time. Once you do a fresh calibration, though, it will happily set things to the current index location.
Quote:
Just accept the stars the HC gives you and move on. The single exception? If the mount offers an alignment star lower than 30 degrees, it's probably a good idea to push "undo" and pick another, higher one.
If you happen to focus on viewing on objects down low, such as finding low planets at sunset, I would in fact use an alignment star near that low area of sky. It depends on what you are doing and where.
Basically doing the simple stuff carefully should work well - but there are ways to finesse and tune the alignment for your specific needs - if that fits your mindset.
Frank
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freestar8n
sage
Reged: 10/12/07
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Quote:
I am interested in learning this as well as how to use the other features of the software as well -- such as the precise goto; sync feature; polar align; RA switch; goto calibration; hibernate; and, home position.
I don't think anyone answered on these features, so I will try on some of the less common ones in your list.
1) Precise goto is like a one-time sync. If you really need tight accuracy for an object, use Precise Goto and center a nearby star. Then it internally syncs on that star and goes to the target object. This is less needed since you can now actually sync permanently on that star.
2) Sync lets you center a star in a region where goto is critical, and you shift the sky model a bit to make goto more accurate on that star. Then, hopefully, other objects in the area will have better accuracy also. If you then move to another part of the sky, you should unsync or sync on a new star in the area.
3) RA switch calibration will improve your initial pointing to alignment stars. You should polar align the mount accurately after aligning well on the mount indexes. Also have the time accurate and the mount level. Then do the RA calibration. It isn't critical, but will help in finding the first stars, especially if it is still daylight.
4) Goto calibration also isn't very critical. It adjusts for the speed of the mount when moving around. It is easy to calibrate and should be done if the weight changes a lot.
5) Home position just sets an arbitrary direction for the mount to move to when you tell it to go 'home.' Normally this only matters in small observatories where the default north pointing direction sticks up too much.
One side point that sort of came up. You can think of your alignment and calibration stars as not moving with the stars over time, but stuck to the sky dome overhead. So if you aligned on regulus early in the night, your accuracy on regulus might reduce over time - but the star that moved into the prior position of regulus will now be accurate.
Again - these are all details, which seems to be what you want - but for the most part everything should just work without much fuss.
Frank
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Tarzanrock
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Reged: 12/07/08
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Loc: Los Angeles
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Quote:
5) If you do want to finesse the accuracy, it will tend to be more accurate around the align/calib stars. So if you are viewing a section of the sky, have some of those stars near it. If you are bouncing all over the sky, use stars all over.
Hi Frank (and everyone else):
First and foremost, let me thank everyone for their helpful comments and interest in these questions. I am sure that anyone who has given these matters any serious thought would like to know how to use this software better than the manner in which it is vaguely described in the literature.
As is stated above, I am interested in finessing the accuracy of the AS CG5 GT Mount with this new software.
I am not interested in using the sofware to locate Messier class objects, I want to use it to locate dim 13th - 15th + magnitude DSO objects under black skies in the California desert this coming Spring; Summer; and, Fall. That being said, I am interested in learning from the experiences of others who have successfully implemented and utilized this software for like purposes. I am particularly interested in knowing the star triangulation patterns they have successfully utilized to obtain pinpoint accuracy -- both for the first initial 2 Star Alignment; and, the second 2 Star Alignment.
I well understand how to set up the Mount and the scope for highly accurate polar alignment via the boresight in the Mount and by visual polar alignment to the NCP with a Polar Scope using Kochab's Clock and other visual alignment methods.
In fact, my Mount and Scope are set up in the same exact location each and every time so the intitial set up is somewhat akin to a pier mount.
I want to learn how to use the new software to perform to its capabilities so that I may have pinpoint accuracy to locate extremely dim objects; so that after the initial accurate alignment process is completed I may observe with the mount and after finishing the observing session, I can hibernate the mount; wake it up the next evening of the following day, etc.
I intend to accurately set the Mount up in the daytime aligning it as accurately as possible to the NCP; and, in that regard, I am interested in learning the solar align function (probably with the Moon and a planet) to begin the alignment process.
Then, at dusk, I will begin the 2 Star Alignment Process.
A. I am interested in learning about highly accurate triangulation star patterns for the initial 2 star alignment with subsequent calibration stars; and, in particular patterns of two alignment stars with 4 calibration stars which others may have successfully employed this time of year, i.e. Mid-May. I am interested in the weekend of the New Moon - May 22nd.
After looking at some star maps, my intial thoughts for the two star alignment are: 1.) Arcturus; Spica; and, Pollux/Castor; or, 2.) Alkaid; Spica; Procyon; or, 3.) Arcturus; Spica; and, Regulus. [I do wonder whether Alkaid is too high in the sky or too close to the NCP for its selecttion for alignment purposes.]
B.) The Polar Alignment Function using Arcturus or Denebola. I would very much like to know others thoughts on this as well as their selection of the polar alignment star.
C.) The Second 2 Star Alignment Process.
This is where the discussion gets the most interesting. Most commentators herein (and elsewhere) think that the 2 star alignment (plus the calibration stars) solves the problem by creating a highly accurate alignment; and, that I shouldn't "fret" over it anymore.
They are probably right -- if one wants to visually look at Messier class objects and the like.
The old Auto 3 Star software was effective for that purpose as well.
However, the fact is, Celestron does recommend a second 2 star alignment with calibration stars.
Further, from my experience with the old Auto 3 Star Alignment process, I believe that the second 2 Star Alignment process (with calibration stars) is a critically essential component for very precise alignment; and, I would like to know how others achieve it and which star triangulation patterns they have successfully used in the course of the second two star alignment procedure for the purpose of achieving the precise alignment we are discussing.
It is the second 2 Star Alignment which presents the interesting quesions.
First, should the second 2 star alignment pattern be selected with the 2 initial alignment stars on the "opposite side" of the celestial meridian from those 2 stars selected the first 2 star alignment?
Second, should the second 2 star alignment stars be selected from a triangulation of stars that are broadly scattered across that half of the sky's meridian? Should the second 2 star alignment be selected from a triangulation of stars that are narrowly scattered across that half of the sky's meridian; and, which calibration stars on the opposite side of the meridian?
Third, should the second 2 star alignment process be in an area of the sky where you are going to visually observe, i.e. such as the southern sky?
Should the second 2 star alignment process be in a certain constellation area of the sky that you are going to be observing?
For a real world example, suppose that you wanted to look at the Virgo that particular evening (like the Virgo Galaxy Cluster) -- should then the second two star alignment process be focused upon the specific area of Virgo by initally aligning, for the second two star alignment, a Smaller Alignment Triangle pattern of stars within the stars of the Virgo constellation itself?
I fully realize that everyone aligns their Mounts differently; and, that there is disagreement upon these questions, but I am interested in learning how others do it because I intend to work this out until I have real pinpoint accuracy.
It seems to me that there must be some general consensus about how, through the use of well thought out, sophisticated and proper star choices, a very effective model of the sky can be created for this new software for:
1.) the initial 2 star alignment procedure;
2.) the polar alignment procedure; and,
3.) the second 2 star alignment procedure for the Spring and Summer skies.
I am interested in doing just this; and, towards that end, your comments and suggestions are greatly appreciated.
William
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waassaabee
Carpal Tunnel
Reged: 11/26/07
Posts: 2702
Loc: Central California Coast
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Are these objects you want to view in the hand controller database?
--------------------
Gary
34N 120W
-My kingdom for blue squares!-
WO Megrez 90FD/TV 0.8x FR/FF
AT8RC
mini Borg 50/Q-Guide/PHD
CGEM
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Tarzanrock
super member
Reged: 12/07/08
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Gary:
I don't know. I'll have to check.
For example, I'm interested in the Quasar in Virgo and the Quasar in Ursa Major, among other distant, dim DSO objects. I don't presently believe that they are listed in the hand control's database, but I will have to check on that.
I am generally aware that Mike Swanson's website has several types of additional data bases which are claimed therein to be applicable for Nexstar software which it is further claimed may be downloaded and integrated into the Nexstar software -- however I am not personally capable of integrating the software. Moreover, I don't know how well these data bases work or even whether or not they may be actually integrated.
Since I'm in Los Angeles, I may ask Celestron's Tech Support to do it for me, when I bring in the Mount itself in to Celestron's Torrance facility to have the Motor Control computer board upgraded.
The Mount is in the desert in Joshua Tree so I can't do it until I next get out there -- which is not likely before the New Moon weekend of 5/22.
I would be particularly interested to know if anyone else has successfully upgraded their software with the databases which may be downloaded from Swanson's website; and, if so, how successfully they integrate and work with the new 4.15 and 4.15 versions of the software.
Where in the Central Coast are you -- near the Santa Ynez River Valley?
William
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waassaabee
Carpal Tunnel
Reged: 11/26/07
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Loc: Central California Coast
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You must have a bodacious scope on that CG5 for quasar hunting!! Why are you upgrading the MC board? You can flash the firmware to upgrade...
I'm in between Buellton and Lompoc.
--------------------
Gary
34N 120W
-My kingdom for blue squares!-
WO Megrez 90FD/TV 0.8x FR/FF
AT8RC
mini Borg 50/Q-Guide/PHD
CGEM
Canon 350D Hap Griffin Baader mod - o.o
My Friend Flickr
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rmollise
Post Laureate
Reged: 07/06/07
Posts: 4575
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Quote:
If you happen to focus on viewing on objects down low, such as finding low planets at sunset, I would in fact use an alignment star near that low area of sky. It depends on what you are doing and where.
Maybe. My experience has been that using alignment stars 30 degrees above the horizon yields better results anywhere in the sky.
--------------------
Uncle Rod
Rod's New Book:
Choosing and Using a New CAT
Available now!
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rmollise
Post Laureate
Reged: 07/06/07
Posts: 4575
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Quote:
You must have a bodacious scope on that CG5 for quasar hunting!! Why are you upgrading the MC board? You can flash the firmware to upgrade...
I'm in between Buellton and Lompoc.
You don't need a big scope for the QUASAR he is talking about. It's (3C273) a starlike object that's at around magnitude 12.8, in range of a 6-inch under good conditions.
--------------------
Uncle Rod
Rod's New Book:
Choosing and Using a New CAT
Available now!
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Patrick
Postmaster
Reged: 05/16/03
Posts: 7808
Loc: Franklin, Ohio
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Quote:
First, should the second 2 star alignment pattern be selected with the 2 initial alignment stars on the "opposite side" of the celestial meridian from those 2 stars selected the first 2 star alignment?
William,
Is there a reason you wouldn't want to select the same alignment and calibration stars that you selected in the first alignment procedure? If the first set of stars were 'ideal' for the initial alignment, do they become less ideal for a second alignment?
Patrick
--------------------
10" f/6 Truss Tube Newtonian
Celestron C6S-GT SCT
AT66ED Refractor
Oberwerk Ultra 15x70 Binocular
475B Geared Tripod & 501HDV Head
Celestron Regal 8x42 Binocular
Canon XSi; Meade DSI;SPC900-NC
Vixen GP2 Photo Guider Mount
My Astronomy Pages
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freestar8n
sage
Reged: 10/12/07
Posts: 299
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Quote:
My experience has been that using alignment stars 30 degrees above the horizon yields better results anywhere in the sky.
The key is that you would be sacrificing accuracy elsewhere for the improvement you find near the alignment stars. So - using a star down low will likely mess up accuracy up high - but if the interest is down low, you should include a star down low. That way the mount gets feedback on flexure, refraction, and more that otherwise it would not include. If you do not intend to look down low, you are better off not going there - as you say.
Frank
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Pedestal
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Reged: 03/11/06
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This is a very interesting discussion. My initial interest in this thread was in how to take advantage of the new firmware features. I have to wonder, however, in all this minutia of alignment analysis, is the mechanics of the mount that good? After all, this is a sub $1k mount here. My ASGT works quite well-but I don't expect Paramount performance. Not trying to start a war, just an observation.
Hubert
--------------------
Hubert
---------------------------------
www.smoggybottom.org
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Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Patrick:
I don't know the answer to the question. That answer and the respective information is what I am trying to ascertain. I do believe that it does matter; and, that a careful second 2 star alignment will improve upon the pointing accuracy.
Celestron claims that because of the software's memory the sky model that is being created will improve with each subsequent alignment adjustment -- so that is why I am interested in using different alignment and calibration stars for the second 2 star alignment process. It seems to me that if the memory improves with each subsequent alignment iteration that such "is" the reason to use a different set of alignment stars and calibration stars for the second 2 star alignment procedure. The question becomes which stars to select to improve upon the first 2 star alignment?
I know that you image so I am wondering whether you have tried doing it this way; and, if so, with what result?
If I could do it tonight I would do so but I simply can't reasonably do it here in Los Angeles.
I intend to do just that the next time I can get out to Joshua Tree to play with the telescope. Unfortunately, it is functionally useless here in downtown Los Angeles due to the massive light dome. For example, last night at 11:00 p.m. the only objects visible to the naked eye were the Moon and Jupiter. See, that nightime photograph in Sky and Telescope a couple of issues back taken from the Mt. Wilson Observatory and you will understand exactly what I am describing about the light dome.
William
Is there a reason you wouldn't want to select the same alignment and calibration stars that you selected in the first alignment procedure? If the first set of stars were 'ideal' for the initial alignment, do they become less ideal for a second alignment?
Patrick
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Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Gary:
Rod is correct. The scope is an 20 cm. Orange Tube Celestron Schmidt Cassegrain. I purchased it from a friend who has sold me some cameras at the Alpine Village Swapmeet in Torrance, CA. It essentially was a gift. He is a retiree from Eastman Kodak. I had previously told him that I was interested in getting a telescope. He obtained the OTA from a close personal friend of his who likewise was himself a retiree from Eastman Kodak.
I am told that the optical tube was specially built by Celestron at his request for purposes of film astrophotography. It came with the original footlocker box; an old Celestron radial guider; and, a Celestron cross-hair orthoscopic reticule. Daniel Mounsey cleaned and collimated the scope. Don Pensack provided an excellent, top of the line, Lumicon 2 inch diagonal. The scope with the diagonal functions at about F/11.70.
The optics appear to be excellent. I can use a Pentax 5 mm XW in that scope with excellent results. Although I haven't tried it, I am cerain that it will likewise handle a 4 mm orthoscopic eyepiece equally as well.
Last year I spent time learning the sky and how to use the scope and mount. This year I want to look deep; and, to do so, I well know that I have to have "very" precise alignment. This is why I am being so persistent in inquiring about the experiences of others with respect to the new software as I do want to know how to use it properly.
Rod is quite correct about the scope and its ability to go deep. I am convinced that it will go to at least the 15th magnitude under very dark black sky conditions in the desert.
William
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Tarzanrock
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Reged: 12/07/08
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Loc: Los Angeles
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Hi:
Don Pensack would agree with you. He has told me "never" pick a star for alignment below 30 degrees because of "refraction" due to atmospheric conditions.
That being said what would you suggest is the upper limit in degrees for star selection? Perhaps its 70 degrees or 75 degrees?
I don't know, but I would assume (and I may well be wrong) that the alignment stars should be selected in the area between 30 and 75 degrees.
Which stars would you select for the intital 2 star alignment (with calibration stars) for the New Moon of 5/22?
Right now I'm thinking of a triangulation pattern of Capella (I know its a bit below the 30 degree line); Procyon or Alphard in the West; and, Arcturus in the East.
The next question becomes which other 2 or 3 calibration stars in the East? Should they be stars in Bootes and Ursa Major? Should they be selected in a triangular pattern?
Then, of course, you Polar Align with the Polar Alignment feature using likely Denebola or Arcturus or ____?
Then you look at the second 2 Star Alignment. Since you aligned the first 2 Star Alignment with the initial 2 stars from the West, do you this time choose 2 stars in the East for the second 2 star alignment with the subsequent calibration stars in the West? If so, then which stars and in what pattern?
This is what I am trying to learn. I am trying to learn whether or not this type of alignment will improve the alignment and the pointing accuracy. I believe that it will and I am very interested to know whether or not anyone has had any such experience with it.
William
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Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Hi Hubert:
The mechanics and engineering of the AS CG5 GT Mount are excellent -- there is nothing wrong with that Mount. If you doubt it, ask Rod Mollise, he's a respected engineer; and, I would be willing to bet a Mercury dime against a $10 bill that he will confirm the above statement. By the way, I saw a brand spanking new Vixen SDX Mount (or whatever they named it) being demonstrated with a brand new Vixen 200 VCL OTA at the Topanga Star Party in February by the Vixen representative. I watched him polar align it for more than 20 minutes with the Vixen polar alignment scope and he thereafter announced it to be perfectly polar aligned. I watched its goto demonstration with its "Starbook" software to center the Trapezium in Orion with its coordinate at my personal request. That telescope had a brand new Televue 13 Ethos eypiece in it. I looked through the eyepiece at the Trapezium. It was not centered, rather it was at the outer edge of the 100 degree eyepiece. It would have missed it completely with a 13 mm Nagler. My AS CG5 GT will do better than that with the old software.
After I learned through trial and error how to set it up last summer; after I learned how to align it with the old auto 3 star alignment process; and, after I did it the way Celestron instructed - auto 3 star; polar align; auto 3 star; precise goto, etc. -- and when I got it right: that mount would point to and center the object in the middle of a 10 mm Pentax XW eyepiece.
That being said, I know that this new software is capable of a lot more and far more precise pointing than the old software once it is properly utilized.
That type of accurate alignment and pointing is going to be necessary in order to look for the deep space objects the type of which I am interested.
William
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Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Gary:
I'm going to bring in the mount to Celestron because they want to upgrade the motor control board by installing new software. I do find Celestron's Tech Support to be exceptional and I like their help. It's about 2 years old so maybe it needs a "check up" just like a car needs a tune-up. Since I intend to keep the mount for a long time I am considering purchasing another motor control board and an on and off switch as I am sure that sooner or later they will give out.
Are you by Los Olivos? I really like it all around that area. Be careful on Harris Grade Road between Lompoc and Santa Maria -- it's a dangerous road there.
Since you and I have about the same longitude and latitude coordinates, I would be most interested in knowing the triangulation patterns of alignment stars you are using.
William
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waassaabee
Carpal Tunnel
Reged: 11/26/07
Posts: 2702
Loc: Central California Coast
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William,
Would you do me a personal favor and first night out just do what the hand controller tells you to do? After that, do the triangulation trick and let us know the differences. I'm very curious to see if it can get any better.
In response to your above...
I do what the hand controller tells me to do. I'm an amateur photographer taking pictures at night. I don't know that much about the sky as I cheat with software.
--------------------
Gary
34N 120W
-My kingdom for blue squares!-
WO Megrez 90FD/TV 0.8x FR/FF
AT8RC
mini Borg 50/Q-Guide/PHD
CGEM
Canon 350D Hap Griffin Baader mod - o.o
My Friend Flickr
Edited by waassaabee (05/07/09 12:13 AM)
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Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Hi Gary:
I intend to do just that -- the difficulty is that I don't get a lot of free time to observe because of living in Los Angeles (its light dome) and the demands of my profession.
I am hoping that I can do it over the weekend of the New Moon - 5/22.
William
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Patrick
Postmaster
Reged: 05/16/03
Posts: 7808
Loc: Franklin, Ohio
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Quote:
Celestron claims that because of the software's memory the sky model that is being created will improve with each subsequent alignment adjustment
William,
Can you give me a reference for that statement? Also, do you have a reference for a 4 star calibration being optimal rather than what Celestron states in their manuals (specifically, 2 stars in the CG5 manual and 3 stars in the CGEM manual)?
Thanks,
Patrick
--------------------
10" f/6 Truss Tube Newtonian
Celestron C6S-GT SCT
AT66ED Refractor
Oberwerk Ultra 15x70 Binocular
475B Geared Tripod & 501HDV Head
Celestron Regal 8x42 Binocular
Canon XSi; Meade DSI;SPC900-NC
Vixen GP2 Photo Guider Mount
My Astronomy Pages
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rmollise
Post Laureate
Reged: 07/06/07
Posts: 4575
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Quote:
This is a very interesting discussion. My initial interest in this thread was in how to take advantage of the new firmware features. I have to wonder, however, in all this minutia of alignment analysis, is the mechanics of the mount that good? After all, this is a sub $1k mount here. My ASGT works quite well-but I don't expect Paramount performance. Not trying to start a war, just an observation.
Hubert
The mechanics of the mount are more than good enough for imaging with a 20 - 25-pound load. As far as them dadgummed minutiae? Forget 'em. Follow the alignment star choices on HC and you will be fine.
--------------------
Uncle Rod
Rod's New Book:
Choosing and Using a New CAT
Available now!
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freestar8n
sage
Reged: 10/12/07
Posts: 299
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Quote:
Don Pensack would agree with you. He has told me "never" pick a star for alignment below 30 degrees because of "refraction" due to atmospheric conditions.
Well - Frank Freestar8n recommends that you choose an alignment star near the area you intend to observe - especially when it is down low - precisely because of refraction and flexure. This may not be true for other mounts, though. No need to worry about triangles or star choices as long as you do 2 alignment stars and 3 or 4 calibration stars.
Anyway - for the faint stuff you apparently are seeking, I assume you will be higher up and this doesn't apply.
Good luck-
Frank
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rmollise
Post Laureate
Reged: 07/06/07
Posts: 4575
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Quote:
Also, do you have a reference for a 4 star calibration being optimal rather than what Celestron states in their manuals (specifically, 2 stars in the CG5 manual and 3 stars in the CGEM manual)?
Thanks,
Patrick
What Celestron says in the manual is "_At least_ two."
Is it optimal to use four? MAYBE. Sometimes. I've found that if Cal Star 3 appears in the eyepiece (I generally align with a 12-mm at f/6.3), which it most often does, I can probably dispense with "4"...
--------------------
Uncle Rod
Rod's New Book:
Choosing and Using a New CAT
Available now!
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rmollise
Post Laureate
Reged: 07/06/07
Posts: 4575
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Quote:
Well - Frank Freestar8n recommends that you choose an alignment star near the area you intend to observe - especially when it is down low - precisely because of refraction and flexure. This may not be true for other mounts, though. No need to worry about triangles or star choices as long as you do 2 alignment stars and 3 or 4 calibration stars.
Anyway - for the faint stuff you apparently are seeking, I assume you will be higher up and this doesn't apply.
Good luck-
Frank
Depends on scope and field of view and other factors. My experience is that after successfully calibrating on 3 - 4 stars, the mount will put _anything_ from horizon to horizon on the very small chip of my Stellacam 2 at f/4 or so with the C8. Visually? Like shootin' fish in a barrel at 100x (my usual "finding" power)...
--------------------
Uncle Rod
Rod's New Book:
Choosing and Using a New CAT
Available now!
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freestar8n
sage
Reged: 10/12/07
Posts: 299
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Quote:
Depends on scope and field of view and other factors.
Hmm - not sure how 'scope enters into pointing accuracy - except through collimation error and internal flexure. I am specifically talking about Celestron mounts that use the 2+N alignment/calibration method. Field of view won't affect accuracy at all - just the ability to tolerate inaccuracy.
My point is regarding the OP's desire to get maximum accuracy - not just in the field of view. The robustness of the alignment you get is good to hear, but it does allow finesse in certain situations. The very issue that makes low stars seem undesirable for alignment is in fact why they are desirable when viewing down low: their positions are distorted in the sky, so they carry good information on that distortion for finding other objects in their vicinity.
A simple demonstration - for these mounts and probably not others - is to align on a star and then goto it. It should return very accurately, and less so for calibration stars, even if refraction and flexure perturb its true location. For this reason, if you want accuracy near an 'undesirable' star down low, you should in fact use it for alignment - but you will lose accuracy elsewhere to improve accuracy locally. If you move to a different part of the sky, you can always replace an alignment star with one there.
But - once again - I think we all agree the pointing should be good enough for his needs just to follow the basic procedures and do a 2+4. Yes, I agree that if the 3rd star is nicely centered, the fourth won't help much.
Frank
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rmollise
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Quote:
Hmm - not sure how 'scope enters into pointing accuracy - except through collimation error and internal flexure.
How? That's easy: a 66-mm f/7, for example, will give a much larger field of view and be far less demanding alignment-wise than a C8 at f/10. You can be sloppy and still have quite acceptable go-tos with the widefield refractor.
My point is that I've _not_ had to use the technique you mention in order to assure good go-tos to objects near the horizon.
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Patrick
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Quote:
What Celestron says in the manual is "_At least_ two."
I'm not trying to split frog hairs here, but the CG5 manual says 'at at least two calibration stars for optimal point accuracy'. To me that means "optimal accuracy can be achieved with two alignment stars, so don't expect to have the best alignment with only one". I think 'optimal' still means 'the best', doesn't it?
The OP has been saying that 4 calibration stars yield optimal accuracy and I'm trying to ascertain where he got that information. If 2 stars do not yield optimal accuracy, then so be it, (at this point, I don't really care ) go ahead and add more cal stars. I can get the kind of accuracy I need from 2+2, polar align, then 2+1, as per the manual. If I've done everything right, when I hit the last cal star it's dead center in my 12.5mm reticle eyepiece through the C6 SCT.
As it stands now, that process takes about 45 minutes. My clear sky time is precious to me since I don't have a permanent setup, and I don't want to waste it trying to improve the accuracy by a couple of decimal places. If one is hunting for a faint object and can't see it, the limiting factor will more likely be the scopes lack of aperture, not that the object isn't in the fov.
Regards,
Patrick
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10" f/6 Truss Tube Newtonian
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freestar8n
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Reged: 10/12/07
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Quote:
I'm not trying to split frog hairs here, but the CG5 manual says 'at at least two calibration stars for optimal point accuracy'. To me that means "optimal accuracy can be achieved with two alignment stars, so don't expect to have the best alignment with only one". I think 'optimal' still means 'the best', doesn't it?
I'm fairly certain the manual is saying that more cal stars are better, but two might be pretty much optimal. (Four would be just as good). So they aren't really using the word optimal correctly. With my cge, I would say the improvement from 3 to 4 is minimal - but when I do critical polar alignment or something, I use 4 because it doesn't take much longer.
They are definitely not saying 2 is the optimal number of cal stars.
Frank
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Tarzanrock
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Reged: 12/07/08
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Hi Guys:
To first respond to Patrick's inquiry -- I did read somewhere, either in some Celestron manual, in some tech support document, or somewhere else on the internet (perhaps on a CN post on another thread or some other astro forum) about the fact that Celestron recommended 2 initial alignment stars plus 4 calibration stars.
It may be that this recommendation was related to the predecessor software version 4.12 -- I simply do not, at this point in time, remember. However, I'll continue looking for the source.
I realize that some think that I am guilding the lily here, but I agree with Frank on this point; and, I do think that it does matter how the initial alignment process is completed.
I further realize that if you follow the 2 star alignment process according to the direction in the hand control device with the new software you likely will put M13 in the field of view of the 31 mm Nagler. That likely is good enough for most people who casually observe, but it is not the point we are discussing.
I, for one, believe that the Mount with the new software is capable of far more; and, I would like to know what it can optimally do when careful alignment is achieved.
Moreover, I believe that optimal performance in terms of pointing accuracy is achieved by certain star selections.
It is clear from Swanson's website (and from what others have commented) that the Nexstar software performs best when the alignment stars are within certain parameters, i.e. above 30 degrees, for an example.
In fact, one commentator on Swanson's site mentions that the alignment is most optimal when the stars are about 100 degrees, or more apart.
So far the 30 degree line seems to be the consensus here.
I generally agree with that analysis, but my question is: if the 30 degree line is the bottom, how high up to the top should the alignment stars be chosen, i.e. greater than 50 degrees; greater than 70 degrees? What is the answer?
That is why I have requested a listing of both alignment stars and triangular star patterns for which people have used in which they obtained highly accurate alignment.
I do realize that the first star alignment pattern (whether you utilize 2+3 or 2+4 stars) will give an accurate alignment.
The issue which I am interested in is how to improve that alignment with the second 2 star alignment. I further think that the second alignment is dependent upon the star selection of the initial alignment.
If, for the initial alignment process, stars in the Western sky, are selected between 30 degrees and 60 degrees at distances of about 100 degrees across the sky, i.e. such as Capella; Alphard; and, Arcturus -- how would you then select the remaining calibration stars in the East?
Would you broadly select stars for a triangular type pattern across several Eastern constellations? Would you narrowly do the selection in one constellation? How would you do it? Would you select them on a North/South basis with the stars located between the 30 degree line and the 60 degree line?
After the initial 2 Star Alignment, you would then would polar align with the All Star Alignment with likely selection of Denebola or Arcturus.
The question for the second 2 Star Alignment process is how would you do it, which stars should best be selected and where?
Since the initial alignment was in selection of 2 stars in the Western Sky, would it be best to pick 2 stars in the Eastern Sky for the second alignment process?
I don't know the answer to the questions about the second 2 star alignment process. Moreover, Celestron's Tech Support couldn't (or wouldn't) answer the questions either.
I don't believe the issue is the time involved in the alignment process since if this software is as accurate as is claimed from the initial 2+3 alignment, it will not take more than another 10 minutes or so to align a few extra stars -- if you know in advance which ones to select.
I think that the issue is knowing which stars should be selected, where they are located and in what order for the software to function optimally.
Swanson's website's downloads of Nexstar's star listings contain a listing of about 240 stars of which about 1/2 apply to the southern hemisphere -- so out of those 120 stars which are located in the northern hemisphere -- there are probably about only 20 or 30 such stars, if that many, which work best for the the purposes optimal alignment at this time of the year; and, I suspect that they probably lay within the 30 degree to 70 degree line. My perusal of star maps show only about 4, 5 or 6 such bright stars in each of the four directions.
The real issue is which of these stars to select; and, in what order are they to be selected.
Perhaps some of you will think about this the next time you align your scope with the two (2) separate 2 Star Alignment procedures which Celestron recommends. I'd like to know how you did it and what results you achieved.
I intend to do the same as soon as I am able to get out of L.A. -- which hopefully will be the New Moon weekend.
William
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rmollise
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Quote:
I'm not trying to split frog hairs here, but the CG5 manual says 'at at least two calibration stars for optimal point accuracy'.
That's not exactly what my documentation says. What it says is:
"Therefore it is usually a good idea to add at least two additional calibration stars to improve the telescope’s all-sky pointing accuracy."
If you're getting good results with two stars, more power to you. Whatever floats your boat. 
I find results better when I use a third star (and a 4th if needed). It doesn't take long to do one more star.
Certainly if you are happy with what you are doing, that's what you should continue doing.
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CounterWeight
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Reged: 10/05/08
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William,
If I understand the question and possible conjecture - here's another 2 cents?
Mounts setup (level / rel north) gets you to->
Intitial alignment. -> gets you set to Polar Align.
Polar Align -> gets you set to Final Align
Final Align gets you to -> Observing, Imaging, Drift Align, or Iterative Align. (If needed or desired)
Accurate time and location are important in initial setup, and whatever error there is [here i am unsure] should be minimized after the initial alignment.
another thought, and this was mentioned by David P when I bought the CGE mount... after completion of PA and 2*4, try the PA again and make adjustment, and then again if desired
A sort of "Lather, Rinse, Repeat". After getting used to the mount, I found repeating the process didn't 'significantly' add to the pointing accuracy if I was careful the first time around - this on a C11 with the 12.5 illum reticle - final cal stars often quite near(by this I mean several star diameters at most) center cross hairs of reticle.
I did have some dialogue with Celestron about accuracy, PA, and goto - no they didn't have a 'best' or 'better' set of align points. My questions mostly related to true celestial North. The mistakes you will make in tiny little things will possibly contribute more to goto errors than the choice of stars and goto model. Here I might agree, and so my only suggestion is that I went to doing the alignment without a star diagonal in the optic path... the difference was minimal as to be nearly insignificant overall. (I think it pays to have a good planetarium program running or good charts of your choice when unsure/unfamiliar of object)
All in all I think the model needs to allow for some error and there will of course be a resulting error or inaccuracy - the important part is does it make a difference in an 11" SCT at high mag? No. Does it cause problems in terms of goto / object location? No. Does that make for a really good and reliable 'goto' system? Yes.
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waassaabee
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I also do my alignments during twilight so not to get cornfuzed! The H/C selects the brighter stars for you, and they are the first ones visible, so why not...
That way I can be aligned, guide camera cal'd and running, focused and take advantage of all the dark sky I can get.
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Gary
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Patrick
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Quote:
That's not exactly what my documentation says. What it says is:
"Therefore it is usually a good idea to add at least two additional calibration stars to improve the telescope’s all-sky pointing accuracy."
This is a direct copy and paste quote from the CGEM manual page 19 HERE
Quote:
Therefore it is usually a good idea to add at least one additional calibration star to improve the telescope’s all-sky pointing accuracy.
emphasis added.
Further down it mentions adding 3 calibration stars for 'optimal' alignment:
Quote:
Although for casual observing it is not necessary to add calibration stars, it
is recommended that you add as many as three calibration stars for optimal
point accuracy.
Perhaps the confusion is coming from the fact that the CG5 manual says it takes at least two calibration stars for optimal alignment and the CGEM manual says three? Or maybe there are different revisions to the manual? The one I'm referring to is the one Celestron has posted on their website.
I don't know...I give up.  
Patrick
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10" f/6 Truss Tube Newtonian
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Chris Rowland
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Reged: 02/28/05
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One thing:
There is no need to avoid stars near the zenith when you are aligning a polar mounted scope. You should avoid stars near the pole. This is because when you are near the pole (strictly where the polar axis of the scope is pointing) small errors in pointing to the alignment star will make large differences in the hour angle axis position.
There isn't any hard and fast rule but I'd avoid stars with a declination greater than 70 deg or less than -70 deg.
For an Altaz mounted scope the zenith should be avoided for the same reason; small errors in pointing can make large differences in the position of the azimuth axis.
By the way William, if you want to evaluate alignment accuracy there's no need to waste valuable dark skies, you should be able to see enough stars to do alignments even in the middle of LA and you can check how well it's pointing by slewing to other stars.
Chris
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freestar8n
sage
Reged: 10/12/07
Posts: 299
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Quote:
How? That's easy: a 66-mm f/7, for example, will give a much larger field of view and be far less demanding alignment-wise than a C8 at f/10. You can be sloppy and still have quite acceptable go-tos with the widefield refractor.
The OP and I are talking about finessing the pointing accuracy, so I am speaking in terms of arc-minutes of error - not "good enough given the field of view." If you go by field of view, it is like becoming a better archer by buying a much bigger target.
Quote:
My point is that I've _not_ had to use the technique you mention in order to assure good go-tos to objects near the horizon.
Again - the OP and I are talking about ways to improve the pointing - whether or not that is actually needed. You seem to get good results using alignment stars above 30 degrees, but you discourage the use of stars below 30 degrees. The issue here is - does pointing to stars below 30 degrees improve when one of those stars is used for alignment. I would say yes and I have given specific reasons related to how the firmware works.
A separate issue, in fact related to the OTA, is that heavier scopes such as my C11 will be more affected by flexure and have greater need for this finesse. This is even more true when imaging with a lot of weight.
I am talking specifically about the recent handcontroller firmware - which came long after the various star selection methods on the NexStar site, and post-dates a lot of anecdotal advice.
This is academic for people searching for faint fuzzies with a lightweight OTA and aiming up high - but might be of interest to others. One application is aiming a scope at the E horizon to capture a moon or planet rising - which is cool to do for those who haven't done it. If you use an alignment star in the area, your local accuracy will be greater than if you had sync'd on a nearby star.
To summarize - for normal viewing and optimal pointing do 2+3 or 2+4 with a reticle eyepiece and finish alignment with up/right motion. Use 2 stars on one side and 3 or 4 on the other. Use the Menu button to switch E/W for alignment stars. Use stars spread out around the sky and don't worry about patterns. If you have special need for accuracy in a region of the sky - high or low - use an alignment star near that area. If you need to polar align, which itself does not improve pointing accuracy much - do a 2+3/4, then polar align, then either start viewing again or do another 2+3/4 if you want maximum accuracy. There is no connection between the stars used for the first 2+3/4 and the second.
Frank
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rmollise
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Reged: 07/06/07
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Quote:
This is a direct copy and paste quote from the CGEM manual page 19 Perhaps the confusion is coming from the fact that the CG5 manual says it takes at least two calibration stars for optimal alignment and the CGEM manual says three? Or maybe there are different revisions to the manual? The one I'm referring to is the one Celestron has posted on their website.
Mine was a cut and paste job, too (from the HC addendum/update); if'n you ask me, they don't have any beter idea of "how many" than we do. 
That bein' the case, the system that I and others have been usin' (when a calibration star appears in the eyepiece or close depending on your setup, you can stop) seems the best idea.
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rmollise
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Quote:
Accurate time and location are important in initial setup, and whatever error there is [here i am unsure] should be minimized after the initial alignment.
Well, kinda. Being accurate is important for landing on Solar System objects and coming close to the initial alignment stars. It really doesn't have much effect on final alignment accuracy, though. IOW, what's on your watch is good enough and "within 60 miles" is good enough.
What I've decided over four years with the CG5 is that what matters most is:
1. Setting the mount on the alignment marks. It really doesn't seem to matter where these marks are so much as that you line up on 'em every time.
2. Use a medium power reticle eyepiece for centering.
3. "Up and right" only for final alignment star centering. You can, of course, use down and left for intitial alignment star maneuvering.
4. A good, freshly charged DC power source. The CG5 is surprisingly power-hungry--more so that my NS11. A weak battery will most assuredly make it act squirelly.
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Uncle Rod
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rmollise
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Quote:
If you need to polar align, which itself does not improve pointing accuracy much - do a 2+3/4, then polar align, then either start viewing again or do another 2+3/4 if you want maximum accuracy. There is no connection between the stars used for the first 2+3/4 and the second.
Frank
Again, if you like what you are doing, and it works for you, more power to you. However, the point of my post is that _I've_ not found dodges like using low altitude stars when observing near the horizon improves accuracy a bit. IOW _in my opinion_ not a help as well as "not needed."
As for polar alignment? I used to add cal stars again on the second polar alignment, but have been told by those who should know that it is not at all necessary. It's purty much academic with the new software's AllStar, anyway, as it works just ducky if you forget the second alignment and just unsync - replace as instructed in the manual...which saves at least some time.
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Uncle Rod
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freestar8n
sage
Reged: 10/12/07
Posts: 299
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A good polar align is not needed for goto accuracy.
A 2-star align will do well for good goto accuracy.
A 2-star align with a mount that has previously been calibrated will do better.
A fresh calibration will be even better, and 2+3 is probably better than a 2+2.
A 2+4 is probably slightly better than a 2+3 - especially if the added cal star is in a region of interest.
After doing an Allstar align, the pointing should be very good without doing anything. The resulting polar alignment will be more accurate if cal stars had been previously added.
If you want to improve the pointing after Allstar, do a fresh 2-star - i.e. replace the alignment stars.
If you want even more accuracy, replace cal stars - but the improvement may be negligible.
A key point here is that doing more may not help much, but it almost never will hurt. Some people have a mindset to do everything possible to optimize accuracy, so the issue isn't whether something is good enough, but can it be improved - and why. I am addressing ways to finesse an empirical improvement in pointing accuracy - which is separate from the subjective, and mount/ota/user dependent issue, of whether or not it is needed or even noticeable.
Frank
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Patrick
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Reged: 05/16/03
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Quote:
That bein' the case, the system that I and others have been usin' (when a calibration star appears in the eyepiece or close depending on your setup, you can stop) seems the best idea
Agreed!
Patrick
--------------------
10" f/6 Truss Tube Newtonian
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wsuriano
member
Reged: 11/13/07
Posts: 79
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Just to let you guys know, from my perspective as a new owner of a CG-5 ASGT, this discussion has been most helpful. With a new mount, you're always trying to solidify the approach you're going to take once you set up. Thanks for the insights
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Meade 8" LX90 GPS w/wedge
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rmollise
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Quote:
A good polar align is not needed for goto accuracy.
A 2-star align will do well for good goto accuracy.
A 2-star align with a mount that has previously been calibrated will do better.
A fresh calibration will be even better, and 2+3 is probably better than a 2+2.
A 2+4 is probably slightly better than a 2+3 - especially if the added cal star is in a region of interest.
After doing an Allstar align, the pointing should be very good without doing anything. The resulting polar alignment will be more accurate if cal stars had been previously added.
If you want to improve the pointing after Allstar, do a fresh 2-star - i.e. replace the alignment stars.
If you want even more accuracy, replace cal stars - but the improvement may be negligible.
A key point here is that doing more may not help much, but it almost never will hurt. Some people have a mindset to do everything possible to optimize accuracy, so the issue isn't whether something is good enough, but can it be improved - and why. I am addressing ways to finesse an empirical improvement in pointing accuracy - which is separate from the subjective, and mount/ota/user dependent issue, of whether or not it is needed or even noticeable.
Frank
I didn't say and don't think I implied polar alignment affected go-to accuracy. It doesn't.
Two stars without calibration stars gives inconsistent accuracy across the sky in my experience.
Replacing the stars following the AllStar per the Celestron instructions works every bit as well.
I agree. I generally do go on to the 4th star.
Depends on how much you had to move the mount. If you moved it a considerable difference to align, your go-to will suffer.
Again, not necessary. Unsync, and replace the alignment as per Celestron works just as well. I know, because I tested the mount down in Chiefland after loading the new software.
See above.
It may not hurt, but I'm usually more interested in gettin' the run underway than I am messing around with stuff that ain't gonna improve things. I am lazy. 
--------------------
Uncle Rod
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Tarzanrock
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Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Guys:
Here is some additional information which I believe is helpful to our discussion:
There is a technical paper on the internet entitled "Two Star Alignment Of A Telescope Explained." I don't know who is the author of this paper. I would attach it but I don't really know how to attach articles. It is noted in the paper that the article was a revision because it states "Rev. 1.1 03/11/2002. This technical paper attempts to to explain the fundamentals, including the math and theory, for 2 star alignment in the altitude and azimuth alignment mode for what I suspect are fork mounted scopes and not german equatorial mounts. It even sets forth a basic generalized equation to position astronomical objects on various equatorial and horizontal planes for precise positioning.
As best as I understand the paper, the author speaks about the computer using "incremental steps each about a sixth or seventh range of "guesses" ... of fractions of 360 degrees after which they should be reduced by a nominal factor of about four each pass and centered about our best fit of the previous range."
The paper further states: "As we find the position of minimum error for each range of calculations we reduce the step, and so the search range either side of the minimum, or recalculate. Each pass will normally reduce the error till eventually, after about six or seven passes, for all practical purposes it can be regarded as zero."
The paper further stated: "This method is not completely foolproof, as the true minimum may be difficult to find in the first couple of passes leading to a highly erroneous reading. Also it is highly dependant on the precision of the telescope controls and drives to accurately centre the alignment stars and measure the slew distance between them as well as the time difference between the readings. An error on sighting of an arcminute or so can make the equation unsolvable which will give a minimum error much larger than zero."
The author next explains: "However the method is 99% safe particularly if alignment stars are selected at least 45 degrees apart and the stars are higher than 25 degrees above the horizon and lower than 65 degrees above the horizon and this method is usually adopted to solve this type of problem."
The author then describes the 2 star alignment method of selecting 2 stars and centering and aligning them which, if I understand the article correctly, he refers to as the "first pass."
The author next explains: "After the first pass is completed we reduce the increment and go through the process again symmetrically about the lowest error point and further reduce for stored error. The process of reducing the increment and recalculating will normally reduce the error to an insignificant figure after a maximum of about six passes. This will produce a calculated hour angle (local sidereal time) and latitude correct to a few seconds of arc for the current altitude of the telescope mount which, with the addition of lapsed time since the last "fix," will allow us to correctly position any other astronomical target above the horizon."
So, the claim is that the computer can correct to a "few seconds of arc" based upon iterative calculations and re-calculations.
It is noteworth that Celestron's technical literature from their 2009 catalogue claims that this new 4.15 and 4.16 software is 24 bit with "0.08 arc second" calculation.
If I understand those numbers correctly that is 8/100th of an arc second -- which, of course, is far better and a lot more precise than the "few seconds of arc" which are identified in the 2002 technical paper referenced above.
I'm no computer whiz, but to me, those numbers clearly imply that this new 4.15 software can be extremely precise in terms of computerized alignment of the mount if detailed care is taken in the alignment process and care is taken in the selection and placement of the right stars to be selected.
On Mike Swanson's NexStar website there is a paper entitled: "Select Alignment Stars for Nexstar Telescopes" by Jean C. Piquette (apparently the readme file was prepared by Mr. Swanson). The readme file was apparently prepared to explain how to use Piquette's "Select Alignment Stars for NexStar Telescopes" computer program. That paper is principally written as an alignment guide for Celestron's "i" series of telescopes (which I suspect are the one-armed forks)and not necessarily the german equatorial mounts. However, I do suspect that the same general theory is applicable here as well to the german equatorial mounts.
The pertinent points contained in that article are as follows:
"NexStar telescopes require the user to center two "alignment" stars in order to build a model of the sky. The accuracy of that model is dependent upon wise selection of those two alignment stars. ... the separation as well as the placement of alignment stars has a dramatic effect on GoTo accuracy."
The article further discusses the angular separation of the first two inital "alignment stars;" and, it specifially notes: "For best results the separation should be a minimum of 70 degrees, but wider than 100 degrees separation is recommended."
The article further discusses the fact that Piquette's computer program assesses a "horizon penalty" to alignment stars near the horizon. It states: "The greatest horizon penalty is applied to stars at an altitude of 15 degrees, which is the lowest altitude for which the HC will present an alignment star. Although the penalty is calculated for all star altitudes, above about 25 degrees the penalty has little effect, and above about 28.5 degrees the penalty is negligable."
There are a couple of other points that are found in Swanson's literature which are pertinent to our discussion. See, the "NexStar Hand Control Version 4 User's Guide" [updated July 6, 2008, Includes Coverage through Version 4.12].
Pertinent to our discussion here is the following statement in the section on Auto 2 Star Align:
"Auto 2 Star Align is a cross between the original NexStar Auto Align and Two Star Align."
Moreover, under the paragraph entitled "Additional Details" it is noted: "Auto Two Star Align will only list objects that fall within the current Filter Limits and 15 - 70 degrees altitude (whichever is more restrictive) as available for alignment. For example, if your Filter Limits are 20 and 90 degrees, only objects between 20 and 70 degrees will be listed."
On page 7 of the article, at the 7th bullet point, it is stated: "It is still important to select widely placed stars for alignment. When selecting your first star, keep this in mind. Selecting a first star high up in the sky will limit the possible separation of the automatically selected second star."
I suspect that some of this information summarized above may be useful to some of you.
Somewhere, someone must have created a computer program which applies this new 4.15 software to german equatorial mounts similar to that which was created by Jean C. Piquette for the Celestron "i" series telescopes.
Does anyone know if such exists or any other website where additonal information pertinent to our discussion may be obtained?
William
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Patrick
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Quote:
this discussion has been most helpful
I've definitely learned some things too.
Patrick
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Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Patrick:
We all have (myself more than anyone); and, we continue to do so -- which expanded knowledge base accrues to all our benefit. Moreover the colloquy is fun as well as enlightening.
Some people enjoy discussions about whether or not a Televue 31mm Nagler is a better eyepiece than a Penatx 30 mm XW -- but, in reality, those issues are pretty much irrelevant if you can't precisely align the mount to place dim, faint objects in the view of the eyepiece.
Last night I pulled out star charts; copied pages; and, today graphed out an initial alignment plan in order to try to precisely align the AS CG5 GT Mount to look for real faint objects in Leo and Virgo for this Spring. Depending upon how this works I'll likely do the same for Cygnus; Saggitarius; Scorpius and other constellations later this coming summer.
I have tried to do it in accordance with the latitude and longitude parameters specified by Swanson; Piquette; Pensack; and, others who have so thoughtfully responded here on this forum.
This "alignment plan" is a first draft and it is far from being complete, but I'm going to set forth the initial thoughts here in case anyone wants to try it out or experiment with it or similar such alignments this coming weekend. I can't do so because I'm stuck in L.A.
I thought that I would begin the 2 Star Alignment starting with Western Stars as Patrick has suggested. This is because I want to use Capella as soon as I can see Capella before it is too far below the 30 degree line.
First 2 Star Alignment:
1.) Capella (early as possible while it is close to the 30 degree line. If not Capella, then Menkalinan (Bootes) 2.) Alphard (Hydra); 3.) Arcturus as the Eastern star. Eastern Calibration Stars: a.) Spica; b.) Mizar (or Kochab - I can't decide - I don't know if Kochab is too close to the NCP); c.) Denebola.
Polar Alignment Function:
Polar Align with Denebola as Patrick has suggested (if not, then Arcturus).
Second Two Star Alignment:
[I thought to align the second 2 star alignment with the first two stars selected in the Eastern sky (opposite the initial selection of Western stars) to broaden the sky model being created.]
1.) Alphecca (Corona Borealis); 2.) Spica; and, 3.) Pollux in the Western sky.
For the calibration stars for the second two star alignment I thought to go to Leo to pinpoint the alignment towards the Leo Triplet (i.e. to test the precision of the alignment with those galaxies):
Western Calibration stars: 1.) Denebola; 2.) Regulus; 3.) Algieba; 4.) Chertan (Chort).
Then I thought about trying the "synch" function on Theta Leonis to further test the alignment function for precision to the Leo Triplet.
I've additionally considered using the Precise GoTo function for the Leo Triplet.
Here is a pertinent question which relates to the precise goto function, when the precise goto slews to the so-called nearby bright star -- what is the magnitude of "bright stars" is Celestron describing? The software must have a quantative limit; and, if so, what is it?
For me, I still have a great deal of difficulty distinguishing through the eyepiece the various magnitudes of so-called nearby bright stars when all faint stars in the vicinity are dim, faint and look quite similar.
For example if I use precise goto on one of the Leo Triplet galaxies, which star will the precise goto slew towards -- will it be Theta Leonis or will it be some dimmer, fainter star nearest to the object galaxy in the Leo Triplet. That is why it would be important to know the the parameters of the magnitude of the "nearby bright star" that the precise goto function slews towards.
I've also considered the Virgo Galaxy Cluster for later on in the evening; and, in so planning I was thinking about the alignment with Denebola; Porrima; Vindemiatrix; and, Zaniah in an attempt to try to bag the Quasar 3C273.
Towards that end, I thought of "synching" on M61 and possibly the 10th magnitude star near the Quaser perhaps by entering the coordinates of the 10 magnitude star.
The question I have here is which set of coordinates are recognized by the new 4.15 software? It is not clear to me. Moreover all of the computerized star atlases use a variety of different sets of coordinates.
William
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Chris Rowland
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Reged: 02/28/05
Posts: 269
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The URL of the paper that William mentions is http://www.geocities.com/barrykgerdes/ALIGNMNT.DOC
At least that's what a Google search on the title of the article gives.
Toshimi Taki has published several papers that are, I believe, the basis for all modern alignment methods, a useful URL is http://www.asahi-net.or.jp/~zs3t-tk/, look for the astronomical computing articles.
And Patrick Wallace has some interesting information about mount error determination and correction - http://www.tpsoft.demon.co.uk/
Chris
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freestar8n
sage
Reged: 10/12/07
Posts: 299
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Hi-
Well - it sounds like there is enough general interest in this stuff that I will reply - but it is a mixture of minutiae and changing context.
I am specifically dealing with the OP's, and others, interest in quantitative improvements, and what helps and what does not, even if by only a little. You keep providing subjective assessments of what is worth doing or not - but that is your own injection of personal taste in what is fundamentally an engineering discussion where opinions are separate. It is also based on your experience, and may not apply to someone with, for example, a weighed down c14 on a cge.
My note was just meant as a breakdown of the choices facing someone using these 'scopes, with indications of the resulting quantitative improvement. It is meant as a guide for someone who either wants a quick and dirty setup, or has time and interest to do all possible.
A 2 star without calibration stars will be much worse than one with calibration stars - and that is why all this stuff about star selection becomes moot when calibration stars are included. 2 star with a mount never calibrated will be very sensitive to star selection and probably not very good in general - but it will get in the ballpark and perhaps be adequate for low power work - particularly near the alignment stars.
Regardless, the very best accuracy comes from a polar aligned mount that has fresh alignment and calibration. This is particularly true if the index positions ever change - either with a cge or cg5.
As for resources on the web for this stuff - I don't know of any that are specific to the methods used in these mounts. Anything discussing "2 star" alignment isn't relevant since it does not include the calibration stars - and this stuff is very implementation specific anyway.
In my own use, for imaging of one area with a fresh setup, I need an accurate polar alignment so I do a careful 2+3/4 alignment. Then I polar align on a star low and in the south - perhaps 30 degrees up. I will then go ahead and replace the alignment stars so that I can read the polar alignment error - which otherwise shows as 0. If that is in the realm of 5' I will goto a star near the target and focus on it, then sync. If I had to move the mount a lot, I might redo polar alignment. Then I frame the target itself and sync on it. That sync is not meant to capture the target location, but the framing of it so I can recover precisely if I ever move the scope. It also lets me recover the guidestar location, which is important for off-axis guiding.
Frank
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Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Chris:
Thank you very much for the research. I'll download those articles and I'll try to read them later this evening.
William
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Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Chris:
Toshima Taki has a fascinating website. Have you used any of his star maps?
William
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Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Frank:
You stated: "I am specifically dealing with the OP's, and others, interest in quantitative improvements, and what helps and what does not, even if by only a little."
I agree. I am very interested in your opinions in these matters.
You further stated: "I polar align on a star low and in the south - perhaps 30 degrees up." I am curious as to which stars you choose for the polar alignment; and, why it is that you pick them so low. Kindly advise.
You also stated: "all this stuff about star selection becomes moot when calibration stars are included."
I'm afraid that I do not understand this statement about mootness. I don't understand why it is now suddenly "moot?"
It seems to me that, assuming that the AS CG5 GT Mount is properly and carefully "calibrated" (and by your use of that term I assume that you mean the R.A. Index Calibration procedure has been completed successfully) -- if so, I would then ordinarily expect that the Mount would now be even more receptive to the inclusion of additional calibration stars within the aforementioned parameters (e.g. star angular separation of a minimum of 70 degrees and preferably >100 degrees; 28.5 degree to 30 degree floor altitude; 65 degree ceiling altitude, etc.); and, I would expect that after the Mount is carefully aligned in such fashion, that it would achieve greater pointing accuracy consistent with its stated technical capabilities of "0.08 arc second calculation" abilities which are referenced by Celestron as such in their most recent catalogue?
William
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waassaabee
Carpal Tunnel
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Posts: 2702
Loc: Central California Coast
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If I had an AP mount (or the likes), I'd worry about some of this schtuff... 
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Gary
34N 120W
-My kingdom for blue squares!-
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rmollise
Post Laureate
Reged: 07/06/07
Posts: 4575
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Quote:
Hi-
Regardless, the very best accuracy comes from a polar aligned mount that has fresh alignment and calibration. This is particularly true if the index positions ever change - either with a cge or cg5.
There is no doubt about that. However, good polar alignment is much less necessary now than it used to be--with the Celestron software, anyhow. Which brings to mind a story I've told a few times...
Me and my buddies was out at our club dark observing site in the wilds of Tanner-Williams, Alabama one rare clear evenin'. Along was a new member and his just-acquired C8 SGT. With a little coachin' from us, he got the scope setup and aligned, and seemed to be havin' a good time. I glanced at a couple of objects in the new scope, and all seemed well. Till he came walkin' over a little later. "Unk, I think there is something wrong with my new scope. She finds stuff OK, but won't track." I went over to check out the situation, and found that he was correct. His scope was placing objects in the field of the 26-mm Plossl at f/10. Maybe not centered, but in there. But they were drifting to beat the band. Now, what the heck? The motors responded to button pushes at all speeds, so I was left scratchin' my noggin. I was rackin' my brain. I shone a red light on the mount, wantin' to check to see if his power connection was OK. "Wait...the polar axis don't look like it's pointed north. Not at all." Turned out he had aligned on Kocab by mistake.
I didn't criticize...I'd done the same thing a while previously with my Sky Commanders on my Dob...and it took me about half an hour to figger out what was wrong...
--------------------
Uncle Rod
Rod's New Book:
Choosing and Using a New CAT
Available now!
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freestar8n
sage
Reged: 10/12/07
Posts: 299
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Quote:
You further stated: "I polar align on a star low and in the south - perhaps 30 degrees up." I am curious as to which stars you choose for the polar alignment; and, why it is that you pick them so low. Kindly advise.
Hi-
I believe this is described in the manuals - but the reason for the choice is that - when doing the polar alignment - you are making alt-az adjustments on an equatorial mount. The mount moves about the vertical axis, and about a horizontal axis that is approximately e/w. To get the most sensitivity from adjustments in those axes, the star should be low and in the south - but not so low that its position is greatly perturbed by refraction. A star in the E or W would be very bad, as would a star overhead. In fact you can use many stars in the sky - but I am talking about an optimal choice. Note that this is the one time you do want the mount fairly level.
Quote:
You also stated: "all this stuff about star selection becomes moot when calibration stars are included."
I'm afraid that I do not understand this statement about mootness. I don't understand why it is now suddenly "moot?"
Some goto implementations and write ups are very simple and just assume a perfect mount that is misaligned, and you use two stars to point. I have a good handle on how the celestron method works - but it is just one of many ways to do it. I think the celestron approach is extremely robust and efficient - and does remarkably well with just 5 or so total stars. Since it is different from other approaches - any recommendations of star pairs to use doesn't apply.
The thing is - I'm not sure of the methodology behind selecting those star pairs in the first place. Unless it was based on real measurements with real mounts - I would be very skeptical.
So - now I will take off my 'optimal' hat and actually make recommendations based on your questions.
The main thing is - these mounts should take very little effort to get very good results. I am not clear if yours is available to use outside right now - but I would just plop the thing down kinda aiming at polaris and then, with a crosshair eyepiece, just go through the procedures and see what you get. I like a 25mm or so crosshair eyepiece because 9mm is too small a view. Do finish motions up/right.
Don't sweat making it too level. Don't sweat polar aligning. In fact - if you sweat at all, something is probably wrong. Just go through the motions under a bad sky with moon and try pointing at some stars. Then you should have a sense of whether you need to improve things. You can use cal stars and polar align and everything. If you have errors in a section of sky, you can sync or try using an alignment star in the area.
The stuff about 0.08 arc second refers to precision in the encoders and motors - but the actual accuracy of the pointing is much bigger. The mounts do amazingly well as they are - but if you truly want pointing in the arc-second range you would need to spend a lot on a mount, and spend a lot more time calibrating it with tons of stars.
With just 2 alignment stars and 3 or 4 calibration stars, and not much work, I think you will have the accuracy you need. If you need more, you can finesse it a bit.
Frank
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freestar8n
sage
Reged: 10/12/07
Posts: 299
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Quote:
However, good polar alignment is much less necessary now than it used to be--with the Celestron software, anyhow.
Yep - it is in a long list of things that only affect the initial pointing to stars. You may have to do a lot of slewing to find the stars when doing the 2-star alignment, but if you go through the alignment procedure with these mounts - the following don't matter "at all" for the resulting goto accuracy:
Time of day, longitude, latitude, level, polar alignment.
It's not that these things can be a little off - they can be hours and tens of degrees off and still get great results.
I put "at all" in quotes because there may be high order effects that would degrade pointing - and the object will race out of the view as you describe - but for the most part they should GoTo just fine.
Frank
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Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Quote:
Me and my buddies was out at our club dark observing site in the wilds of Tanner-Williams, Alabama one rare clear evenin'.
Hmmm, Tanner-Williams, Alabama -- is that something like "being stuck inside of Mobile with the 'dark sky' blues again?"
Check out Bobby's new record album, it's not too bad.
William
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rmollise
Post Laureate
Reged: 07/06/07
Posts: 4575
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Quote:
Hmmm, Tanner-Williams, Alabama -- is that something like "being stuck inside of Mobile with the 'dark sky' blues again?"
Check out Bobby's new record album, it's not too bad.
William
I've listened to and loved a lot of his music over the years, and I am all in favor of Old Guys, but I must admit that I have a hard time makin' out what he's singin' on the new one.
As for TW...we are very lucky to have reasonably dark (the west, anyway) skies within less than an hour's drive.
Edited by rmollise (05/09/09 04:39 PM)
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Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Quote:
To get the most sensitivity from adjustments in those axes, the star should be low and in the south - but not so low that its position is greatly perturbed by refraction. A star in the E or W would be very bad, as would a star overhead. In fact you can use many stars in the sky - but I am talking about an optimal choice.
Frank: I am most interested in "optimal choices." I do understand how to use the AS CG5 GT Mount; and, I have used it quite successfully with the old software. I am most interested in "optimal choices" for using the new 4.15 and 4.16 software.
That being said, how high up would you recommend picking the polar alignment star in the South?
I understand what Mr. Pensack, yourself and others say about the 30 degree horizon limits due to "refraction" and other issues. Others state that the selection of the polar alignment star needs to be selected close to the celestrial meridian. The question is approximately how close to the celestial meridian and how high up in the sky? The other question is which star would be optimal to select for the polar alignment star?
Initially and based upon the suggestions of others, I thought Denebola would be a good choice -- but looking at the star chart -- Denebola is 70 degrees, would this be too high in the sky under your criteria? Denebola is however quite close to the celestrial meridian.
The other choices appear to be Zaniah and/or Porrima in Virgo at about 52 degrees to 55 degrees, with Zaniah being the closest to the celestial meridian.
Should one go lower to about the 30 degree line for the selection of the polar alignment star?
Which stars are your choices for the optimal polar alignment star wherein you yourself have obtained highly precise alignment?
You further said: "I will take off my 'optimal' hat and actually make recommendations based on your questions."
Actually, I would prefer if you would put you "optimal" hat back on as this is exactly what I am interested in. [Moreover, I'd like Rod Mollise to take off his cowboy hat off and put on his engineering cap as I don't like to see all of that fine engineering talent and training qualitatively expressed with the simplified down home, "ah shucks" good ole boy, point the telescope north at the sky stuff. I'm more than certain that Rod has thought this through rather completely; and, I would like to know which stars and in what order he would select to optimally align the mount as we have be discussing.]
Frank, I can't use the Mount/scope now because it's in the desert at Joshua Tree and I'm in Los Angeles. So, I can't immediately test it. When I do have the opportunity I shall do such.
I do have a 25 mm cross-hair eyepiece and two 12.5 mm reticuled, illuminated eyepieces; and, with the use of a barlow, I believe that I can achieve highly accurate and very precise star alignments which star alignment coordinates will thereafter be entered into the mount's computer.
The question becomes "which stars" to select; in which "location" in the sky; and, in which "order" to achieve the optimal pointing accuracy that we are seeking to obtain.
Towards that end and to summarize, the recommendations have generally been: stars between 30 degrees and 65 degrees with a very wide separation, i.e. a minimum of 70 degrees of separation to a separation of greater than 100 degrees with the largest separation the recommended one to choose.
I undertand how to select the stars for the first 2 star alignment procedure. There are unresolved issues which pertain to the selection of the calibration stars for the first 2 Star Alignment procedure. See, my prior post above.
The remaining issues concern the same questions for the second two star alignment procedure. This is where the difficulty lies.
I wonder how you (and others) do this second alignment procedure. The forum here has been pretty silent on this issue. Perhaps it is because many people simply do the 2+3 alignment and are satisfied with it. It appears that this may the case for many people. While the 2+3 two star alignment may be satisfactory for most people, I am interesed in refining it or, as you say, "finessing it," to try to obtain greater accuracy.
I have a couple of planetarium programs: The Sky, version 6; and, Starry Night Pro. I've printed out sky maps from them and I've plotted triangular alignment patterns on them as expressed in my previous post above.
As soon as I can figure out how to draw those lines on those charts (with Adobe; powerpoint, or some other Microsoft or Corel program) I'll try to attach them here so you and others can visually see precisely what it is that I am talking about.
Lastly, you will note that my ineptitude in being able to effectively use the simple "quote" mechanism here on this forum is likely directly proportional to my inability to figure out how to use computer programs.
William
Edited by Charlie Hein (05/10/09 08:50 AM)
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Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Quote:
I've listened to and loved a lot of his music over the years, and I am all in favor of Old Guys, but I must admit that I have a hard time makin' out what he's singin' on the new one.
Rod:
That much has been pretty much true since his "first" album. I like them all 'cause he pretty much sounds like me when I sing.
Take another look at what I wrote in post number 3093106. I'm interested in your engineering analysis on this issue. Take your time and seriously think about it. There is no rush to this. I'm very interested about learning how to properly use this new software with this Celestron AS CG5 GT Mount; and, I want to use this mount to perform to what I believe its engineering is capable of performing when the new software is intelligently applied.
I don't share the viewpoint of some that it is a "cheap" mount or that it is incapable of performing fine alignment the degree to which we have been discussing.
William
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bdjeep
sage
Reged: 01/29/07
Posts: 440
Loc: Bolton, MA
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I'm not sure I understand the point of all of this. It's fine to want to understand the inner workings of the mount software, and I commend you on your effort. Learning is a great part of this hobby.
However, what are you trying to accomplish? I understand you want to view faint objects visually, but that alone does not set a requirement for sub arc minute pointing accuracy. The CG5 is perfectly capable of putting objects very near the center of a low power eyepiece. A "precise goto" will land them within the FOV of a CCD chip. What more do you need?
What exactly are your pointing accuracy requirements? And why do you think the CG5 is not capable of meeting your needs without an extreme analysis of alignment star choice?
Have you considered the list of other factors such as gear backlash, encoder/gear accuracy, flexure and mirror shift, and atmospheric seeing/refraction effects? Are you able to measure these effects?
If you really want to get better pointing accuracy, then I suggest you look into software such as TPoint. After alignment on several dozen stars you may be able to achieve accuracy in the single arc minute range, but you will hit the limits governed by the factors mentioned above. And by the time you have completed that process, your viewing time will be greatly diminished and the astronomer next to you will have already viewed dozens of faint galaxies, quasars, and other such objects.
I think it's great to want to get the most out of your mount, but to what end?
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rmollise
Post Laureate
Reged: 07/06/07
Posts: 4575
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Quote:
Rod:
That much has been pretty much true since his "first" album. I like them all 'cause he pretty much sounds like me when I sing.
Take another look at what I wrote in post number 3093106. I'm interested in your engineering analysis on this issue. Take your time and seriously think about it. There is no rush to this. I'm very interested about learning how to properly use this new software with this Celestron AS CG5 GT Mount; and, I want to use this mount to perform to what I believe its engineering is capable of performing when the new software is intelligently applied.
I don't share the viewpoint of some that it is a "cheap" mount or that it is incapable of performing fine alignment the degree to which we have been discussing.
William
I will certainly take a look at your post, but my opinion mirrors that of the contributor above. There is only so much you can get out of the CG5 without runnin' into the realm of the impractical for minimal returns. Using the standard methods of alignment and the "precise go-to" function, my CG5, even with the old "three star" software, would reliably place anything I wanted on the (near webcam-sized) chip of my Original Meade DSI. Sure, you can spend a lot of time redoin' alignments, and spendin' more money and time with stuff like t-point, but I don't think your are gonna do appreciably better _enough_ to make a difference with either visual or imaging work. The mount can get an object on the chip, so I'd rather just keep on truckin', maybe spendin' 30-seconds centering my object in the frame than hours of hair pullin' tryin' to fashion silk purses out of sow's ears.
Let me say, HOWSOMEEVER, that I will not naysay your quest. It's folks like you who advance the art and science of amateur astronomy, not lazy ol' houndogs such as myself.
--------------------
Uncle Rod
Rod's New Book:
Choosing and Using a New CAT
Available now!
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bdjeep
sage
Reged: 01/29/07
Posts: 440
Loc: Bolton, MA
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Quote:
Let me say, HOWSOMEEVER, that I will not naysay your quest. It's folks like you who advance the art and science of amateur astronomy, not lazy ol' houndogs such as myself.
Well said, Rod. And to this end, I'd suggest that the original poster purchase or borrow some of the more advanced books on the subject if he wants to learn more. A web forum is not the easiest place to start talking about the complicated mathematics of telescope control. I think the number of people with expert knowledge on these subjects are in the minority here, and I'm not one of them.
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Tarzanrock
super member
Reged: 12/07/08
Posts: 159
Loc: Los Angeles
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Guys:
This is not that difficult and it is not that complicated. It is really quite simple. There are only about 10 or 12 stars which need to be selected within the parameters of 30 degrees and 65 degrees which have a reasonable distant separation.
Attached is a chart of a star alignment plan which
hopefully, will simplify these issues.
First is the 2 Star Alignment beginning
in the West, as suggested by Patrick, and others. The red lines represent the path of the initial star selections: 1.) Capella (or Menakalin); 2.) Alphard; and, 3.) Arcturus.
The Calibration stars are in black: a.) Spica; b.) Mizar (or Kochab - but I don't know whether Kochab is too close to the NCP?); and, Denebola.
Next follows the Polar Alignment function. Patrick likes to use Denebola so I selected it. Others like Arcturus. Frank says to polar align with a star low in the south. The question is how low -- between 30 and 50 degrees? The other questions are which star and how close should it then be to the celestial meridian?
Therefter comes the second Two Star Alignment process as recommended by Celestron. Some assert that it makes no difference which side to do the second alignment on. I suspect that it might make a difference in the creation of the sky model.
Since I intitially aligned beginning in the West, I chose to start alignment in the East with the blue lines representing second alignment path: 1.) Spica; 2.) Alphecca; and, 3.) Pollux in the West.
The issue becomes how to choose the calibration stars. Since I am interested in the Leo Triplet to test the alignment I thought about setting the calibration stars around and near the Leo Triplet and thus chose: a.) Denebola; 2.) Regulus; 3.) Algieba; 4.) Chertan/Chort.
The next idea was to utilize the "Synch" function with likely Theta Leonis to hone in on the galaxies of the Triplet.
The questions in looking at the Star Chart and this alignment are:
A.) What about the northern sky for the sky model? Should stars be chosen in Draco (although they are obviously dim to pick at dusk); and, what about the use of Kochab in Ursa Minor? Is it too close to the NCP to use with the new 4.15 software? What about the use of the stars of the bowl of the Big Dipper -- are they likewise too close to the NCP for use in alignment?
No one needs a computer and no one needs a slide ruler to figure this stuff out -- all that is needed (and all that has been asked since my initial questions) what stars should be selected, where in the sky and in what order to optimally align the AS CG5 GT Mount.
Based upon pragmatic, practical experience some of you out there must have successfully aligned your mounts according to the procedure set forth by Celestron with the two separate 2 Star Alignment processes. To the extent that you have succeeded with highly accurate alignments, I simply would like to know what stars you used and how you did do it.
Further, after looking at the chart, you may have better ideas than I do about this; and, if so, I certainly would like to know about them.
Thanks,
William
Edited by Charlie Hein (05/10/09 09:27 PM)
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WadeH237
sage
Reged: 02/24/07
Posts: 499
Loc: Snohomish, WA
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William,
If you want to talk about the mathematics of the pointing model, that's a perfectly interesting topic.
I replied very early in the thread with my suggestions to easily get accurate pointing with the CG5. At that time, I didn't recognize that this was a discussion about math and not a "how do I get my new mount to work" topic. I do worry a bit that someone new to the hobby might see this thread and come away with the impression that the CG5 is difficult to use - which could not be farther from the truth.
Just last night, I set up my CG5, did two star alignment with 4 calibration stars using the suggested stars. Then I did the polar alignment using Procyon. The whole process took less than 10 minutes. For the rest of the night, the mount put every target near the center of my 12mm eyepiece at 170x. I couldn't have asked for more.
Certainly, the large number of responses on this thread are an indication that it's interesting, but the title might be a bit misleading of its nature. I'm guessing that the "why bother" replies are from people (like me, initially) who are interested in the correct steps to get good pointing in the most practical way.
Just my two cents,
-Wade
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http://www.faintfuzzy.net
Stuff
Visual Stuff (shared with wife and kids, 10 & 12): Generic 6" F/8 Dob, C8-SGT, CGE-1400, Orion ED80 on a CG5-GT, Coronado PST, 6" Meade Schmidt-Newtonian, Astroscan, 12x70 Binoculars.
Imaging Stuff: Meade 8" LX200ACF with Optec TCF-S focuser on a CGE mount, SBIG ST-10XME with CFW8 and remote guide head, Astro-Tech AT66ED guide scope, Astrodon filters, QHY8PRO, DSI Pro, Canon EOS 20D, Hyperstar 3 for C8.
Edited by Charlie Hein (05/10/09 09:28 PM)
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CounterWeight
Pooh-Bah
Reged: 10/05/08
Posts: 1298
Loc: PDX chronoplast
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Wade,
I couldn't agree more - especially when the OP could do this himself and post any relevent results. I think I clearly defined a verifiable method in a previous post (one I used when I got my CGE and my CG5ASGT). I think asking us to do it is a no-go as we get what we need time and again, month after month, different OTA's, different locations, different everything.
I'll just say here again - that I do not think there is the single case optimum (singularity) being asked about as there are way, way too many factors that have nothing to do with the celestial sphere and who lives where on it. Celestron understood this and gave us 'what we need'. I think the mathematical proof that a single optimum would also show that it is a very poor idea That would mean anything else would not be as good.
Tarzana - you say it's simple... We are telling you - yes, absolutely it is simple. It seems you don't want to accept that?
To answer your question about what 2 stars (that some of us must have used)... that has changed month by month as it should (or depending on what time of night we align) - and as everyone here it seems is trying to get through to you - whatever is chosen - the results are quite adequate. All over the place, with all kinds of folks, using all kinds of stuff. Simple - it works.
I think you may agree after some 'quality time' with your mount, but no amount of pencil pushing will make a difference until you do that.
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CGE (Frankenmount mod.)
Onyx 80ED, Tak FS-128 #02058, TEC APO160ED #030
CCD: Orion SSPDSCIv2, SSI3, SSAG
diags, ep's, tubes, filters, Binocs
My CN Image Gallery
Experience is a difficult teacher, it gives the test first, and gives the lesson later
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donsinger1
sage
Reged: 10/28/07
Posts: 298
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You are overanalyzing this...go out and have fun!:)
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Fun Stuff:)
Portland, OR
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