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Problem of star trailing with loaded CGE Pro Mount

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#1 ejjh

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Posted 06 March 2013 - 12:40 PM

I have a problem: I have a telescope setup...see photo...wherein I cannot get it balanced in RA and DEC in order to track. No matter what placement of accessories (I want to do EVERYTHING with one setup.... solar image with a Coronado PST with a IS DMK 41AU02 monochrome camera, lunar and planetary imaging through a 6" Celestron OTA (piggybacked) with a DFK 21AU04.AS USB CCD color camera, and deep sky imaging with a HyperStar lens and Starlight Xpress M25C with a 14" Celestron scope...all of this atop a CEG Pro mount on a permanent pier. However, no matter how well balanced I can get various configurations of accessories place , when I take continuous images in Maxim DL, stars track to the left on my monitor in as little as 2 seconds. I have four 22lb counterweights, with the Hyperstar inside the Astrozap dew shield. I have two view finder scopes...an Antares 7.5 x 50mm illuminated right angle correct image finder scope and the an illuminated one that came with the C1400, and a Telrad finder. I also have two Crayford focusers. The CGE Pro mount has a payload capacity of 90 lbs. Before I added the extra equipment, I was able to take pretty fair images with the HyperStar and was able to track for a minute without any trailing. You can see them at www.hahnenberg.org. It has been suggested that I retry polar alignment or take off the heavier PST or OTA. I have done both of the latter, but have not rechecked polar alignment. I don't think that is the problem since my polar alignment was accurate before I began adding things. It has also been suggested that I've got too heavy a load or that I double mount the PST and OTA. I am looking for some serious help. Ed

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#2 DuncanM

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Posted 06 March 2013 - 02:19 PM

Have you tried mounting the 6" SCT on a rail so that you can slide it forward for balancing. Something like this:
http://www.scopestuff.com/ss_pigy1.htm
http://www.scopestuff.com/ss_mral9.htm

#3 jrcrilly

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Posted 06 March 2013 - 02:42 PM

I have a problem: I have a telescope setup...see photo...wherein I cannot get it balanced in RA and DEC in order to track.


Two things:

You need to get it balanced before trying to use it, How bad is it? I suspect that with all that stuff on top of the OTA you don't have sufficient counterweight for RA balance.

You say it drifts "to the left". That doesn't tell us anything useful. Is the drift in RA, dec, or both? If it is in dec then you aren't polar aligned and need to fix that before trying to use it.

#4 ejjh

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Posted 06 March 2013 - 04:20 PM

Duncan...The OTA is mounted on a Losmandy dovetail plate. The OTA came with a dovetail rail, so I can move it forward or back.

#5 ejjh

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Posted 06 March 2013 - 04:29 PM

John...There is nothing on top of the OTA. The OTA does have a Crayford focuser on its end which does add weight to the 20 lb OTA.

No matter what I do, the drift of stars on the monitor moves from right to left in RA or DEC. I'm beginning to think that I need to polar align again.

I went on your website. Your M31 is great. I took the attached photo with my HyperStar and Starlight Xpress for a combined time of 5 min. I would just like to get back to where I was before I added all the new stuff. What should I keep and what should I get rid of? What would you advise to make my setup an ALL IN ONE setup?

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#6 DuncanM

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Posted 06 March 2013 - 05:52 PM

So if you loosen the clutches, with the counterweight shaft horizontal, the OTA remains in place, and doesn't move in either RA or DEC? In other words the mount is perfectly balanced? If this is the case, then your mount may have slipped and ruined your polar alignment.

#7 ejjh

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Posted 06 March 2013 - 06:07 PM

Duncan ... That just may be the case. Since I won't get out to do polar aligning because in NW lower Michigan we get so many fronts coming off Lake Michigan, I may have to wait a few weeks for a cloudless night.

I'm rather new to how Cloudy Nights has expanded. Can I ask how you came across my post? It seems there're are 1000s of threads these days.

#8 Whichwayisnorth

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Posted 06 March 2013 - 06:36 PM

Well I.. hmmm Ok I have to say this the right way.
First, I would take everything off EXCEPT the main OTA and your imager. Get that all balanced where DEC is in perfect balance and RA is very slightly east heavy. Now try to image and see how it goes. If there is still a problem then you are probably talking about the gear meshing loosening up or something like that. You'll either need to adjust it yourself or send it back to Celestron and have them play with it for a month. If things look good then add one item, re-balance (slightly east heavy each time) and check again. Each time it passes the test add one more thing. Remember to clear and retrain PEC too. If your values are all before you added all that stuff it won't work.

Good luck

Edit: OH and yah, of course check your polar alignment and double check it.

#9 DuncanM

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Posted 06 March 2013 - 07:39 PM

Duncan ... That just may be the case. Since I won't get out to do polar aligning because in NW lower Michigan we get so many fronts coming off Lake Michigan, I may have to wait a few weeks for a cloudless night.

I'm rather new to how Cloudy Nights has expanded. Can I ask how you came across my post? It seems there're are 1000s of threads these days.


Remember, that I'm talking about how mount is balanced with the counterweight shaft "horizontal" not "vertical" as in your picture.

I just decided to take a look, and came across your post quite by accident.

The other thing is, if you leave your mount running at the sidereal rate, while the dec shaft is vertical, as in your picture, does the mount slowly move in RA, as it should?

#10 ejjh

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Posted 06 March 2013 - 08:00 PM

Duncan...I've had one cloudless night since I added everything. I can't answer your question because of the weather. I used Precise Go-To to Capella. Everything I tried, the drift away from it could even be seen in Telrad Finder.

#11 laconicsax

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Posted 06 March 2013 - 08:06 PM

I'm not sure I understand how you got to where you are--at what point in adding things did the balance become impossible?

If the balance and tracking is good with just the C14, start with that and add things one-at-a-time, re-balancing in between each. It'll be tedious, but you'll be able to easily find out where the problem is.

#12 DuncanM

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Posted 06 March 2013 - 08:14 PM

Duncan...I've had one cloudless night since I added everything. I can't answer your question because of the weather. I used Precise Go-To to Capella. Everything I tried, the drift away from it could even be seen in Telrad Finder.


You don't need to open your observatory to test balance or to check if the mount is running at the correct speed. Just start the mount and let it run at sidereal rate - it should rotate in RA at 15 degrees per hour ( or one hour of RA)and it should be easy see the movement after even a few minutes.

#13 ejjh

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Posted 06 March 2013 - 09:25 PM

Laconicsax ... That I will try.

#14 wolfman_4_ever

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Posted 07 March 2013 - 01:07 AM

Hi ejjh.

The side by side bar is from adm accessories. link

To browse the forums, go to the top of this page and click on forums. Then a list of forums shows up, this post is in the mount forum. Your other post where your original question was posted was in the Beginning and Intermediate Imaging forum.

Your image post is not big enough but it looks like field roatation. Its hard to tell but are your top stars trailing like \ and your bottom stars are trailing like / ?? That would indicate polar misalignment. If all the stars are trailing one way, it's usually flex ,poor balance, etc..

You do know how to balance the scope correct? Your picture of your scope really looks like it rear heavy with all the attachments and scopes on the rear...

#15 ejjh

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Posted 07 March 2013 - 03:16 AM

Dave...Thanks for the side by side link. Dean of Starizona spent quite some time on the phone instructing me how to balance in RA and DEC. While my photo appears to show a butt-heavy setup, there is a very heavy Hyperstar and camera combo at the nose end of the 14" OTA under a dew shield. Stars trail in one direction. Will keep at it. Here's another photo...

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#16 EFT

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Posted 07 March 2013 - 10:22 AM

While I don't think that balance is the problem causing star trailing (it is more likely alignment or flexure), you do want the mount to be reasonably well balanced for best performance. In that regard, one thing to keep in mind is that the further the wieght on the mount is from the top of the saddle, the less the capacity of the mount actually is. In other words, a 40 pound scope that is only 6 inches in diameter, is much different than a 40 pound scope that is 14 inches in diameter in regards to the mount's ability to handle the load. With everything you have stacked on there, you would probably be better off using a side-by-side setup that will lower the center of the load closer to the mount head. SBS systems can be tricky to work with themselves, but in this case, you would probably find things to be better overall. In the long run, while it might be nice to have everything mounted together, you may find it to not be very practical due to the potential issues it can add.

#17 ejjh

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Posted 07 March 2013 - 12:04 PM

Ed Thomas...I had contacted Celestron Technical Services and asked to explain my problem to Rick Garrison, a designer of the CGE Pro. Here was Celestron's response:

Thank you for contacting Celestron Technical Services.

We regret to hear you are having tracking problems with your CGE-Pro. Sometimes adding extra equipment can cause flexsure in the system when the scope is pointing at certain angles which is hard to avoid. The mount has a feature called mount calibration under utilities. After the alignment calibrate the mount if weight is added or removed.

I would assume that I should re-polar align the mount (2 + 4) with the equipment I want on it whenever the next cloudless night occurs, then go to Utilities and re-calibrate the mount.

At this point I googled up the question "When should I use the CALIBRATE MOUNT utility? What does it do?"

Celestron's answer online is: There are two functions in the CALIBRATE MOUNT submenu. Depending on exactly what mount you have and the hand control firmware version, the first one is called RA SWITCH or RA INDEX CALIBRATION. The second function is GOTO CALIBRATION.

RA SWITCH corrects for any error in the placement of index marks (Advanced GT or CG-5, CGEM) on the mount housing or the position of the RA index switch inside the mount (CGE or CGE Pro). This will help the mount to more accurately find the two stars it uses for sky alignment when starting up an observing session.

RA SWITCH should be run when you are finished aligning the scope. It just needs to be done once, as the information is remembered by the mount’s hand control. Your next alignment will be easier once you’ve done it.

GOTO CALIBRATION does just what the name says: it changes the final motions of a GOTO to compensate for imbalances cause by any heavy accessories attached to the scope to keep GOTO times short. It should be used whenever you are reconfiguring your scope and cameras, heavy binoviewers, guidescopes, etc. It is also remembered by your mount’s hand control.

Now, I am confused. Should I use GO-TO CALIBRATION? If so, then what do I do? Will that give me the 00-00-00?

#18 EFT

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Posted 07 March 2013 - 12:57 PM

The GOTO calibration is worth a try, but I have never heard of having to do it as often as they are recommending. If that were necessary I'm sure a lot of people would be compaining about it. Realistically, you may never get to 00-00-00, but if it is a flexure, mirror shift, etc., problem I don't see how even a calibration will help since such problems are not inherently consistent, even when not changing your setup.

The best thing to do at this point is to try to star narrowing down what component or setup is causing the problem. If you had no problem with an earier setup, go back to that setup and ensure that you still have no problem with it. You may find that you do now. If not, then start adding things one component at a time until the problem starts to appear. The problem with a setup that is a complex as yours is that it gets to be impossible to pin point a problem area so you need to start eliminating possibilities. You could do that by working backwards (removing items), but since you had a working system before, I would start from there and work forwards instead.

#19 ejjh

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Posted 07 March 2013 - 03:36 PM

Ed Thomas...Thanks. I think your advice is what I will follow. I will close this thread for now until I get this worked out. Everyone has helped give me advice. I thank all who did. I may wind up eliminating some of my add-ons. I don't want to give up imaging with the HyperStar, the Coronado PST, and at least one finder. I did learn how to navigate Cloudy Nights better!

#20 wolfman_4_ever

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Posted 08 March 2013 - 12:16 AM

2+4 star calibration is not polar aligning. Once you finish your 2+4, slew to a stat near the meridian and Dec 0 and then hit the align button, then choose polar align, then follow tge directions. The 2+4 star calibration is a star model for the mount, not polar alignment.

#21 Cliff Hipsher

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Posted 08 March 2013 - 09:52 AM

2+4 star calibration is not polar aligning. Once you finish your 2+4, slew to a stat near the meridian and Dec 0 and then hit the align button, then choose polar align, then follow tge directions. The 2+4 star calibration is a star model for the mount, not polar alignment.


Amen Brother! Preach it! If your hand controller does not prompt you to physically adjust the mount in Alt and AZ (like my LXD75 does for a 1 star alignment), you are not doing a Polar Alignment.

I tripped over this for a long time and could not figure out what was "wrong" with my mount.

What it boils down to is Polar Alignement affects TRACKING which explains why folks serious about AP prefer drift aligning.

All this felgercarb about 2, 3, and 4 star alignments and calibration stars is about generating a pointing model for GoTos.

Basically, your Polar can be off and GoTos can be spot on and vice versa. What matters for long exposure imaging is the accuracy of your Polar alignment, and here is an easy way to prove that.

Fire up your mount, and do a Polar alignment, then do a drift. DO NOT run any of the multi-star "alignments". Use the hand controller and slew to a star, any star. Get the star centered and then walk away. Come back 15 minutes later. Barring any errors in the gear train the star should be right where you left it.

If the star has drifted you can run what ever test motors/calibrate motors/train drive/ PEC train functions your mount has and then run this test again.

#22 ejjh

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Posted 08 March 2013 - 06:13 PM

Dave...I understand all of that and have done the 2 + 4 several times for various reasons. In the sequence of events that follows, one is prompted to polar align with the All-star Polar Alignment. I had tried drift alignment and Kochab method and others, but the Celestron method gave me the best results. What may be a problem on my mount is the knob which points down vertically (see photo) that determines latitude. I had to insert a piece of metal and glue it in order to get latitude correct because the knob and and screw were not long enough and use a pipe wrench to adjust. There is a guide which is not very accurate. Doing polar alignment watching the monitor in Maxim DL with 1 sec or less continuous exposures, I get the crosshairs dead on the alignment star, going back and forth with latitude knob and the horizontal logitude knob which work very easily. I did get 00-00-00 and tracking from then on was quite exceptional. My observatory is at 44 degrees; 81 min North latitude and 85 degrees 42 minutes West longitude.

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#23 WadeH237

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Posted 08 March 2013 - 07:06 PM

Um, did you not realize that the plate for the altitude adjustment can be moved?

Celestron ships the mount with it in the upper position, which works from low latitudes, to about 45 degrees. That silver plate at the top of the circle in your picture can be moved into a lower position for higher latitudes. I believe that there a 4 hex bolts on each side that you need to remove, and then re-add in the lower position.

-Wade

#24 EFT

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Posted 08 March 2013 - 07:08 PM

Dave...I understand all of that and have done the 2 + 4 several times for various reasons. In the sequence of events that follows, one is prompted to polar align with the All-star Polar Alignment. I had tried drift alignment and Kochab method and others, but the Celestron method gave me the best results. What may be a problem on my mount is the knob which points down vertically (see photo) that determines latitude. I had to insert a piece of metal and glue it in order to get latitude correct because the knob and and screw were not long enough and use a pipe wrench to adjust. There is a guide which is not very accurate. Doing polar alignment watching the monitor in Maxim DL with 1 sec or less continuous exposures, I get the crosshairs dead on the alignment star, going back and forth with latitude knob and the horizontal logitude knob which work very easily. I did get 00-00-00 and tracking from then on was quite exceptional. My observatory is at 44 degrees; 81 min North latitude and 85 degrees 42 minutes West longitude.


Looking at your photo I see why you had trouble with the latitude adjustment. The plate that the adjustment knob screws into can be moved further down in order to adjust to higher latitudes. If you look at the side of the base casting there are two holes further down on each side for mounting the plate. Simply remove it from the current location and attach it in the lower location and then the knob will be long enough to reach your latitude and will also push the axis housing at a better angle. With the additional wieght this could actually be a flexure point for you since the angle between the knob and the contact plate gets lower as the latitude gets higher. Adding addition wieght with the knob threaded all the way in could actually cause some flexture.

#25 wolfman_4_ever

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Posted 08 March 2013 - 07:10 PM

You can move that plate, that the latitude bolt goes through, to the bottom of the mounting brackets. Thats listed in the manual for high latitutes. Yes, polar aligning in altitude can be tough when the mount is fully loaded.

You polar align the mount and not the telescopes. Take off all but your little finder, if weight is an issue, and polar align.






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