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Equipment Discussions >> Mounts

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inZet
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Reged: 02/12/09

Loc: Milan, Italy
Pointing accuracy
      #6061364 - 09/03/13 05:26 PM

How do you achieve max pointing precision using a GOTO telescope? Intended as a star in the dead center of the eyepiece, to avoid confusion.
I may be wrong, I'm not so convinced a good polar alignment will suffice.
Having swapped out the old Sphinx StarBook board with a NexSXD my pointing precision has improved a lot, but still within 30 arcsecs or so. If I set the camera to 640x480, I could miss the double. Visually, I can zoom out and in, swap the eyepieces and so on, no problem other than the doubt I observed the right double...


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JAT Observatory
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Re: Pointing accuracy new [Re: inZet]
      #6062306 - 09/04/13 08:50 AM

You need a pointing program like T-Point or Max Point .

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Eddgie
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Re: Pointing accuracy new [Re: inZet]
      #6062483 - 09/04/13 11:17 AM

Spend a lot of money on an AP or a Paramont or other high end mount. That is one way.

Pier mount your existing EQ head. I believe that of the pointing accuracy is related to flexure of the tripods, especially with so many people overloading mounts these days. Sure, you can use calibration stars, but done be surprised if stars that center in a 31mm Nagler are not centered in a 6mm Ortho. Just the weight of the eyepeiece can deflect a mount a few arc minutes. Even my CGE will deflect with an eyepiece change.

Putting the mount on a pier will take a lot of that away.

But these may be impractical. I mention them because if you really want perfect centering, that is the bar you need to get over.

Otherwise, what can you do?

Hypertune your mount. Replace the bearings with higher quality bearings and end-float the shafts properly.

Check the worms to ensure they are not bent, and check the end float here.

Lap the worms and worm wheels with a fine lapping compound. Of course this is painfully tedious, and this is the kind of thing that high end mounts get that you won't get from mass market mounts.

The lapping is necessary to ensure that you can get the most precise worm gear mesh to the worm wheel. The lash between these gears is a crucial issue for real high accuracy pointing and you do get some pointing inaccuracy, especially if you have light and heavy eyepeices.

Pre-load. Do not perfectly balance the mount. You want enough weight on the gear faces so that they always settle with the same faces in firm contact.

Use a stiffer dovetail setup. If you are using a light aluminum dovetail, try going to a heavy or solid one.

I also eliminate cone error. It is not supposed to matter because the calibration routines are supposed to correct for this, but I find it helpful.

Do not use vibration suppression pads. Asymetric loading can cause very slight deflections when the scope is in different orientations.

I mean you requirement is for arc-second accuracy, and to get it will be very painful.

Or very expensive. A paramount on a concrete pier would be easier because you are going to do all of these things above and still not get 5 arc second pointing accuracy.

Sorry Charlie.


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Spacetravelerx
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Reged: 12/23/12

Loc: New Mexico
Re: Pointing accuracy new [Re: inZet]
      #6062505 - 09/04/13 11:37 AM

Quote:

How do you achieve max pointing precision using a GOTO telescope? Intended as a star in the dead center of the eyepiece, to avoid confusion.
I may be wrong, I'm not so convinced a good polar alignment will suffice.
Having swapped out the old Sphinx StarBook board with a NexSXD my pointing precision has improved a lot, but still within 30 arcsecs or so. If I set the camera to 640x480, I could miss the double. Visually, I can zoom out and in, swap the eyepieces and so on, no problem other than the doubt I observed the right double...




inZet,

Basically Eddgie is spot on. However I would like to add the LX850 to the list. My goto's are spot on. Per the spec it is +/- 1 arcminute for gotos, but all of mine have been dead center. When I get back home I will post a video on this (I will use the MallinCam software with the target window to show this).

Of course this is not a cheap option either.


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jrcrillyAdministrator
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Re: Pointing accuracy new [Re: Spacetravelerx]
      #6062511 - 09/04/13 11:41 AM

http://sourceforge.net/p/astrotortilla/home/Home/

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rmollise
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Re: Pointing accuracy new [Re: inZet]
      #6062557 - 09/04/13 12:20 PM

Quote:

How do you achieve max pointing precision using a GOTO telescope? Intended as a star in the dead center of the eyepiece, to avoid confusion.
I may be wrong, I'm not so convinced a good polar alignment will suffice.
Having swapped out the old Sphinx StarBook board with a NexSXD my pointing precision has improved a lot, but still within 30 arcsecs or so. If I set the camera to 640x480, I could miss the double. Visually, I can zoom out and in, swap the eyepieces and so on, no problem other than the doubt I observed the right double...




The long and the short of it is it depends on which scope/mount you are talking about. Some go-to GEMs require a good polar alignment for good go-tos, and some don't, for example.

I would guess you mean 30 arc-minutes. 30 arc seconds would be pretty dadgum good.

The main secret with the Celestron system? Do all four cal stars and always finish centering with the up and right keys only.


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orlyandico
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Re: Pointing accuracy new [Re: rmollise]
      #6062577 - 09/04/13 12:31 PM

well as pointed out by others, backlash in the worm engagement, flexure of the tripod and optical tube, mirror flop if it's an SCT, will all contribute to inaccurate pointing.

the "best" way is to GoTo the desired star, plate-solve, calculate the error, than RCAL the mount. then do another GoTo. even Paramounts are required to do this in my experience (with GRAS/iTelescope) in order to obtain best pointing accuracy. Out of the gate, the Paramount ME "only" gets about 1' to 2' pointing accuracy, and that's with a very, very good polar alignment.


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Phil Sherman
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Re: Pointing accuracy new [Re: orlyandico]
      #6062622 - 09/04/13 12:56 PM

If you need to get absolute pointing accuracy, then you have at least three solutions.

1. Buy an AP or Paramount mount - lots of $$$.
2. Buy an Atlas or EQ6 mount and use EQMOD to point it.
3. Download, install and learn how to use AstroTortilla (a plate solving software suite) to tell you exactly where the scope is pointed. You'll need to take a short test exposure to pass to AT for analysis but it'll tell you exactly where you're pointed. If your scope is being run using the ASCOM platform, AT can move your scope to your intended target.

Phil


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WillCarney
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Re: Pointing accuracy new [Re: Phil Sherman]
      #6062748 - 09/04/13 01:58 PM

I recently found that once I balance the scope I never seem to set the scope in the exact park location. So on my Atlas I will do a one star alignment first then park and turn off. Then do a three star. This is much more accurate since the mount is parking in it's correct position. Of course proper polar alignment is important. Which I have struggled with.

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rmollise
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Re: Pointing accuracy new [Re: orlyandico]
      #6062751 - 09/04/13 02:01 PM

Quote:

well as pointed out by others, backlash in the worm engagement, flexure of the tripod and optical tube, mirror flop if it's an SCT, will all contribute to inaccurate pointing.

the "best" way is to GoTo the desired star, plate-solve, calculate the error, than RCAL the mount. then do another GoTo. even Paramounts are required to do this in my experience (with GRAS/iTelescope) in order to obtain best pointing accuracy. Out of the gate, the Paramount ME "only" gets about 1' to 2' pointing accuracy, and that's with a very, very good polar alignment.




That may help if very tight pointing accuracy is required. A normal a normal 2+4 alignment will put anything from one horizon to the other in the field of a medium power eyepiece or on the chip of my Mallincam Xtreme. "Up and right," BTW, is how Celestron takes backlash into account; fooling with gears is not required.

The ME doesn't have the calibration/cone stars that the Celestron and some other mounts implement. That why the Bisque mounts require a tight polar alignment and other measures if they are to have good go-to performance.


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rmollise
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Re: Pointing accuracy new [Re: WillCarney]
      #6062759 - 09/04/13 02:04 PM

Quote:

I recently found that once I balance the scope I never seem to set the scope in the exact park location. So on my Atlas I will do a one star alignment first then park and turn off. Then do a three star. This is much more accurate since the mount is parking in it's correct position. Of course proper polar alignment is important. Which I have struggled with.




Parking/home position will affect how close the mount comes to its initial alignment stars, but will not affect final go-to accuracy.


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rmollise
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Re: Pointing accuracy new [Re: Phil Sherman]
      #6062765 - 09/04/13 02:06 PM

Quote:

If you need to get absolute pointing accuracy, then you have at least three solutions.

1. Buy an AP or Paramount mount - lots of $$$.
2. Buy an Atlas or EQ6 mount and use EQMOD to point it.
3. Download, install and learn how to use AstroTortilla (a plate solving software suite) to tell you exactly where the scope is pointed. You'll need to take a short test exposure to pass to AT for analysis but it'll tell you exactly where you're pointed. If your scope is being run using the ASCOM platform, AT can move your scope to your intended target.

Phil




1. Those are great mounts mechanically, but Celestron's go-to system is considerably more sophisticated.

2. EQMOD works very well, but so does Celestron's NexStar system.

3. For some applications that is the answer, but for me, the standard Celestron alignment is good enough in that it puts objects on my small chip cameras reliably.



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Moromete
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Reged: 02/15/12

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Re: Pointing accuracy new [Re: rmollise]
      #6062783 - 09/04/13 02:14 PM

Rod is right. Unfortunately Celestron still has no competition when it comes to go-to pointing accuracy. Celestron software is still the most complex when using HC only. Skywatcher/Orion are still lagging behind in software go-to precision.

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Footbag
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Re: Pointing accuracy new [Re: Moromete]
      #6062795 - 09/04/13 02:21 PM

My CPC's pointing was considerably better then my AP Mach 1. The Celestron mounts have pointing models built into the firmware. To get that pointing accuracy out of a AP mount, you will need additional pointing software.

I never had any issue getting perfectly centered targets on my CPC. With my Mach 1, I use additional software to help me point at targets. The targets are close, just not smack in the center.

I do have a non-orthogonal system which impacts pointing with a system without a pointing model.


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Spacetravelerx
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Reged: 12/23/12

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Re: Pointing accuracy new [Re: Moromete]
      #6062802 - 09/04/13 02:25 PM

Quote:

Rod is right. Unfortunately Celestron still has no competition when it comes to go-to pointing accuracy. Celestron software is still the most complex when using HC only. Skywatcher/Orion are still lagging behind in software go-to precision.




Um, I have to dispute this claim "Celestron still has no competition...".

My LX850 provides excellent gotos (i.e. spot on), and I am pretty certain the same is true for the LX600. Like I said, once I am back home in New Mexico I will use my MallinCam to show how good the Meade setup is.

I cannot speak for all the other Meade units, but I simply have wonderful gotos on my LX200 and LXD75, though qualitatively speaking the LX850/LX600 are better. This is also one of many reasons I chose Celestron over Meade.

Anyways, stay tuned for the video later this month or October (the monsoons have been massive) - you will see what I mean.


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Spacetravelerx
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Reged: 12/23/12

Loc: New Mexico
Re: Pointing accuracy new [Re: Spacetravelerx]
      #6062805 - 09/04/13 02:28 PM

Quote:

Quote:

Rod is right. Unfortunately Celestron still has no competition when it comes to go-to pointing accuracy. Celestron software is still the most complex when using HC only. Skywatcher/Orion are still lagging behind in software go-to precision.




Um, I have to dispute this claim "Celestron still has no competition...".

My LX850 provides excellent gotos (i.e. spot on), and I am pretty certain the same is true for the LX600. Like I said, once I am back home in New Mexico I will use my MallinCam to show how good the Meade setup is.

I cannot speak for all the other Meade units, but I simply have wonderful gotos on my LX200 and LXD75, though qualitatively speaking the LX850/LX600 are better. This is also one of many reasons I chose Celestron over Meade.

Anyways, stay tuned for the video later this month or October (the monsoons have been massive) - you will see what I mean.





Oh and I forgot to add - the accurate gotos (spec is +/- 1 arcminute) are with the stock LX850/LX600. No need for a separate computer or software. "It just works"...


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jrcrillyAdministrator
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Re: Pointing accuracy new [Re: Spacetravelerx]
      #6062817 - 09/04/13 02:38 PM

Quote:

Oh and I forgot to add - the accurate gotos (spec is +/- 1 arcminute) are with the stock LX850/LX600. No need for a separate computer or software. "It just works"...




It does work well, and it's so convenient. I'm sure that C will add this capability to their very affordable Starsense system soon - and I've been saying for a while that such capability will become an expected feature in midrange gear in the near future.


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Whichwayisnorth
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Re: Pointing accuracy new [Re: jrcrilly]
      #6062842 - 09/04/13 02:53 PM

I concur that the Starlock system puts objects dead center (or close enough). I think the theme of this thread is how can you take an existing mount that doesn't have Starlock and get accurate pointing. The answer has already been given. Make sure your hardware is tight, eliminate flexure, make sure your Cogswell Cogs and Spacely Space Sprockets are working the best they can and if all else fails get Astro Tortola. One more thing that was already mentioned and is very important. Something center at a short focal length will not necessarily be centered at a long one. For instance, my little 80mm refractor F/4.8 typically has targets in the center(or close enough) but when I use my F/10 SCT they not.

Edited by Whichwayisnorth (09/04/13 02:54 PM)


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rmollise
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Re: Pointing accuracy new [Re: Spacetravelerx]
      #6062885 - 09/04/13 03:22 PM

Quote:



Um, I have to dispute this claim "Celestron still has no competition...".

My LX850 provides excellent gotos




He means "by telescope companies who are still in business."

JUST KIDDING. Maybe.


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Eddgie
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Re: Pointing accuracy new [Re: Spacetravelerx]
      #6062941 - 09/04/13 03:59 PM

The OP said he is getting 30 arc seconds now, but does not satisfy him. I would be thrilled with 30 arc second pointing, but apparently he is not.

I think he is aiming at "dead center" meaning maybe +/- 5 arc seconds or so?

I don't know. 30 arc seconds is pretty good to me though.

I am lucky to get 10 arc minutes out of the CGE.


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jrcrillyAdministrator
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Re: Pointing accuracy new [Re: Eddgie]
      #6062954 - 09/04/13 04:09 PM

Quote:

The OP said he is getting 30 arc seconds now, but does not satisfy him. I would be thrilled with 30 arc second pointing, but apparently he is not.




He's apparently shooting at only 550mm so he'd never notice a 30 arcsecond error; that'd be only 15-20 pixels. I just presumed he got the unit of measure wrong.


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gdd
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Reged: 11/23/05

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Re: Pointing accuracy new [Re: jrcrilly]
      #6063160 - 09/04/13 06:07 PM

Other than using pointing software, how about doing a GOTO an easily identifiable star near the intended target, sync to it, then do one more GOTO - would that get you close enough?

Gale


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inZet
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Reged: 02/12/09

Loc: Milan, Italy
Re: Pointing accuracy new [Re: Eddgie]
      #6063228 - 09/04/13 06:57 PM

Thank you all for the answers! Mods moved my post, I almost missed it... :-)
I mainly observe and measure double stars. To be sure I'm measuring THAT double a good pointing precision is important, otherwise errors can be performed.
My setup is very lightweight. I have a short tube (WO Megrez 90), rings, dovetail, ASI120 webcam, cables. 5 Kilograms payload at most, the Sphinx SXD specs are 15 Kg max.
I observe from my backyard, on grass. Tripod is HAL130, aluminium, it seems sturdy but who knows? I never thought about flextures. It may be a land subsidence, do you believe pieces of wood under the tips may help?
Balancing is a nightmare, axes are frictioned, they come very tight from Vixen. However, if possible I unbalance east to let the gears to always be in traction.
The SXD is not an HEQ5, it is supposed to be well-build (???), in fact I'm not aware of an hypertune: the weak link in the chain is the electronic, but replacing the StarBook with the NexSXD solves all the problems and transforms the mount in a Celestron AdvGT/CGE Pro. I've not bought the HC, I'm using NexRemote software to control the mount.
I don't have too much money to invest, AP is not a solution.
Even with the best mechanic I learned from you it's hard to achieve necessary precision; a plate solve is required. The question is if a solve can be found even if small fields are imaged.
The camera has 3.75 um pixels, imaging scale is 1.3 arcsec/pixels, near the scope's resolution limit.


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inZet
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Reged: 02/12/09

Loc: Milan, Italy
Re: Pointing accuracy new [Re: gdd]
      #6063251 - 09/04/13 07:14 PM

Good idea to sync on a near star. Because I usually observe nearby doubles, I should need to sync only one time per zone.

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jrcrillyAdministrator
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Re: Pointing accuracy new [Re: inZet]
      #6063265 - 09/04/13 07:21 PM

Quote:

Good idea to sync on a near star.




Just turn on the "Precise goto" function in the controller. That won't get you within 30 arcseconds but it will get you closer than you are now if you aren't using it - probably within an arcminute or so.


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inZet
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Reged: 02/12/09

Loc: Milan, Italy
Re: Pointing accuracy new [Re: Eddgie]
      #6063306 - 09/04/13 07:57 PM

I meant arcmin, of course. 30 arcsecs is the separation of Albireo... I only want to get the double in the field, I don't do position measurements. :-)

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WesC
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Re: Pointing accuracy new [Re: jrcrilly]
      #6063308 - 09/04/13 08:00 PM

So far the only thing that affects my CGEMs gotos are how well I align those calibration stars and tripping over the tripod in the dark!

If I get those two things right, my gotos are well within 20% of the center of my 11mm Nagler. And if I need dead-center tracking, I just sync to that object.

Good enough for me.


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jrcrillyAdministrator
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Re: Pointing accuracy new [Re: inZet]
      #6063309 - 09/04/13 08:00 PM

Quote:

I only want to get the double in the field, I don't do position measurements. :-)




Precise goto will get you where you need to be without having to buy anything.

As soon as C integrates the starsense with the precise goto function it will be automatic. Then I'd buy the Starsense.


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rmollise
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Re: Pointing accuracy new [Re: inZet]
      #6063489 - 09/04/13 10:26 PM

Quote:

I meant arcmin, of course. 30 arcsecs is the separation of Albireo... I only want to get the double in the field, I don't do position measurements. :-)




I don't know about this rig you are using, a Vixen with somebody's motor control board that allows you to use the NexStar HC, but Celestron's mounts will EASILY get your target in the field of such a small wide field scope if the alignment is done correctly.


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orlyandico
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Re: Pointing accuracy new [Re: rmollise]
      #6063539 - 09/04/13 11:11 PM

He's using the ASI120 which has a teeny tiny chip (probably equal to or smaller than a Mallincam chip). I think his problem is more of the soft ground (yes, wood under the tripod tips would help) and maybe not using UP and RIGHT for all final alignment corrections.

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rmollise
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Re: Pointing accuracy new [Re: orlyandico]
      #6063955 - 09/05/13 09:00 AM

Quote:

He's using the ASI120 which has a teeny tiny chip (probably equal to or smaller than a Mallincam chip). I think his problem is more of the soft ground (yes, wood under the tripod tips would help) and maybe not using UP and RIGHT for all final alignment corrections.




Good catch...


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Jon_Doh
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Reged: 09/16/11

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Re: Pointing accuracy new [Re: Spacetravelerx]
      #6064032 - 09/05/13 09:43 AM

Quote:

Quote:

Quote:

Rod is right. Unfortunately Celestron still has no competition when it comes to go-to pointing accuracy. Celestron software is still the most complex when using HC only. Skywatcher/Orion are still lagging behind in software go-to precision.




Um, I have to dispute this claim "Celestron still has no competition...".

My LX850 provides excellent gotos (i.e. spot on), and I am pretty certain the same is true for the LX600. Like I said, once I am back home in New Mexico I will use my MallinCam to show how good the Meade setup is.

I cannot speak for all the other Meade units, but I simply have wonderful gotos on my LX200 and LXD75, though qualitatively speaking the LX850/LX600 are better. This is also one of many reasons I chose Celestron over Meade.






I have to agree. I've used both systems and Meade is way ahead of Celestron on ease of alignment and even the fine tuning process. Meade's Easy Align uses two stars that the GPS finds for you and it is as accurate as Celestron's 2+4 system..

Celestron is a popular option for refractors and why they can't simply their alignment process and make it more like Meade's is beyond me.


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rmollise
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Re: Pointing accuracy new [Re: Jon_Doh]
      #6064188 - 09/05/13 10:58 AM

Why? Part of the reason is that Meade sued them over their GPS 2-star alignment process for alt-az GPS scopes.

The other part is that for a _GEM_, a two-star alignment really doesn't work worth a frak.

Edited by rmollise (09/05/13 11:33 AM)


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Stew57
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Re: Pointing accuracy new [Re: rmollise]
      #6064197 - 09/05/13 11:02 AM

And I have found the Celestron alignment easy enough and accurate to better than +-5 acrminutes. Granted the only Meade goto I am familiar with is the ETX80 I have so I won't compare accuracy, but for ease I wouldn't say it is all that much easier.

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inZet
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Reged: 02/12/09

Loc: Milan, Italy
Re: Pointing accuracy new [Re: Stew57]
      #6076588 - 09/12/13 09:17 AM

Wood under the tripod tips helped for sure.
Two days ago one of the rays that sustain the accessory tray broke, so I suspect the crack caused lack of rigidity.
Repaired in time for a quick check, now I can have the pointed object within 10 arcmin from the center of the eyepiece.


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Gil V
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Reged: 09/09/12

Re: Pointing accuracy new [Re: inZet]
      #6076659 - 09/12/13 10:03 AM

What is an acceptable error for visual use, in your opinion? Is 5-10 arcminutes acceptable? I've just installed DSCs and I'm still in the learning curve.

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rmollise
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Re: Pointing accuracy new [Re: Gil V]
      #6076754 - 09/12/13 11:00 AM

Yes, 10 or 15-minutes is pretty good.

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Gil V
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Reged: 09/09/12

Re: Pointing accuracy new [Re: rmollise]
      #6077269 - 09/12/13 03:24 PM

Thanks, Rod. I measured about nine arc minutes of error in my Dynamax mount over 12 hours. Frankly, I'm suprised it wasn't a lot worse.

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Ranger Tim
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Reged: 03/25/08

Loc: SE Idaho, USA
Re: Pointing accuracy new [Re: Gil V]
      #6077989 - 09/12/13 11:25 PM

You are using a reticle eyepiece for your reference stars, correct? I use a 9mm reticle eyepiece and get great go-to's with both my Sphinx and my GM-8. Most are dead center unless I am flopping back and forth over the meridian. Error tends to build if I work both hemispheres alternately. I stay in one then switch.

With a reticle ep for alignments I can get my mount set-up for a visual run easily. When imaging I use a camera and zoom the live view to the maximum to center alignment stars. Hey, it works!


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inZet
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Reged: 02/12/09

Loc: Milan, Italy
Re: Pointing accuracy new [Re: Ranger Tim]
      #6079098 - 09/13/13 05:09 PM

I use a webcam and a software that plots a reticule on the screen. It's far more precise than eyepieces.
Beware to use full CCD resolution; most drivers use the upper-left frame only. For example if your camera has a 1280x1024 pixels and you select 640x480, you bet those pixels aren't in the center of your imaging area.
The result is, if you use a flip mirror, you could see the star not in the center of your eyepiece! Or, if you align based on 640x480 setup, it's like to align with the star not in the dead center of your eyepiece -- you can imagine the effect on pointing precision.

Gianluca


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oo_void
professor emeritus


Reged: 11/13/09

Loc: San Francisco, CA
Re: Pointing accuracy new [Re: jrcrilly]
      #6079421 - 09/13/13 08:59 PM

Quote:

http://sourceforge.net/p/astrotortilla/home/Home/




I agree with this one ... for ultimate pointing accuracy, plate solving is your friend.


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Doug Murphy
member


Reged: 10/07/07

Loc: Leesburg, VA
Re: Pointing accuracy new [Re: oo_void]
      #6134527 - 10/13/13 09:03 AM

Would Celestron's StarSense finder allow me to get 4-5 arcmin accuracy on my CPC 925 Edge HD mount?

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Stew57
Carpal Tunnel
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Reged: 05/03/09

Loc: Silsbee Texas
Re: Pointing accuracy new [Re: Doug Murphy]
      #6134674 - 10/13/13 10:23 AM

Iget better than that with a standard alignment with my CGEM. After adding the SSA it is just a bit better than the standard alignment. I am getting around 3 arcminutes or better.

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Raginar
Post Laureate
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Reged: 10/19/10

Loc: Rapid CIty, SD
Re: Pointing accuracy new [Re: Stew57]
      #6134683 - 10/13/13 10:25 AM

That's a spendy tool for that kind of a change how were your giros with precise goto on?

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Stew57
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Reged: 05/03/09

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Re: Pointing accuracy new [Re: Raginar]
      #6134724 - 10/13/13 10:47 AM

It does not increase the pointing accuracy that much but it will do the alignment for you. It will also allowa high precision mode (adding calibration point) for the desired object, much easier. They do have bigger plans for it. It is missing a working ASPA at the moment. Now as to whether it is worth it at that price point for you, only you can answer that

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Raginar
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Reged: 10/19/10

Loc: Rapid CIty, SD
Re: Pointing accuracy new [Re: Stew57]
      #6134743 - 10/13/13 10:53 AM

Yup.i agree. I guess I'm surprised at the number of people who find alignment troublesome.

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Doug Murphy
member


Reged: 10/07/07

Loc: Leesburg, VA
Re: Pointing accuracy new [Re: Raginar]
      #6134811 - 10/13/13 11:33 AM

My CPC 925 Edge arrives today, so have not used it yet. I do Mallincam imaging and had been using an Obsession truss Dob reflector, and although I could get pointing down to 4 arcsec on favorable nights, the system would settle and then objects were not in the FOV. The field was 17 arcmin with the reflector, so I needed 4 arcmin pointing accuracy to make life tolerable. I am hoping to get that on the CPC mount, so was thinking of the new StarSense.

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frank17601A
member


Reged: 04/16/11

Re: Pointing accuracy new [Re: Doug Murphy]
      #6134942 - 10/13/13 12:45 PM

What is needed is a Celestron Pro Division. They would slightly modify their handcontroller software and maybe motor controllers and sell that to folks like AP, Bisque and Losmandy.... I am sure I am oversimplifying it but why could not the Celestron HC software be modified to input gear and worm parameters etc? They could sell this technology to AP, Bisque. etc....and let these folks do the mechanical heavy lifting that they are so good at! The Celestron software even make the current overseas machining and assembly work reasonably. Imagine Celestron HC linked to the AP/Bisque/Losmandy quality!

Have you tried to buy a new AP handcontroller........1000 bucks! Retail....I can buy a new Celestron handcontroller....100 bucks...

Please don't move to have me executed!!! Imaging how good drivers etc would get when the software guys would only have to bother with ONE set of drivers for everyone..

I have owned AP, Bisque and Celestron, and quite frankly the Celestron HC is the most intuitive and full featured...

Just my opinion, let the arguments begin!

Frank

Edited by frank17601A (10/13/13 12:47 PM)


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Moromete
professor emeritus


Reged: 02/15/12

Loc: Romania
Re: Pointing accuracy new [Re: frank17601A]
      #6135154 - 10/13/13 02:32 PM

Does anyone have experience and knows how good is pointing accuracy with a EQ6 PRO+C11 at ~100x magnification with firmware 3.35 on both sides of the meridian?

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rmollise
Postmaster
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Reged: 07/06/07

Re: Pointing accuracy new [Re: Moromete]
      #6135341 - 10/13/13 04:24 PM

Quote:

Does anyone have experience and knows how good is pointing accuracy with a EQ6 PRO+C11 at ~100x magnification with firmware 3.35 on both sides of the meridian?




I have not had the opportunity to try 3.35, but the previous version would, with a decent (polar scope) polar alignment, put anything I requested in the field at this magnification. IF...

The secret is giving the SynScan the alignment stars it needs. The suggestions in the manual are more than that:

Stars 1 and 2 should be separated by at least 3-hours of right ascension. Also, try to pick two that are at least 20-degrees apart in declination, but separation in RA is more important.

Star 3 needs to be within a declination range of 30 and 70 degrees north and south.

More recent SynScan firmware is better at offering choices of alignment stars that fulfill the above, but still don't just blindly accept the first stars offered unless they do.


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Moromete
professor emeritus


Reged: 02/15/12

Loc: Romania
Re: Pointing accuracy new [Re: rmollise]
      #6135378 - 10/13/13 04:46 PM

Thanks Rod.

You give me more confidence in Synscan GOTO accuracy but I'm still a little afraid of its performance after beeing used CG5-GT excelent GOTOs even with a C11 after a 2+2 star alignment and a bad polar alignment. I now Synscan requires you to put Polaris in the little circle of the polar scope to give a good GOTO precision, unlike Celestron HC.

I feel like changing a Mercedes with a Chevy.

Have you tested the GOTO accuracy with EQ6+C11(F3.3)+Mallincam and see if DSOs land somwhere on Mallincam's frame all over the sky or you tried only the EQ6+C8(F3.3)+Mallincam?

How good is GOTO accuracy in this situation compared to a Ceelstron mount?


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rmollise
Postmaster
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Reged: 07/06/07

Re: Pointing accuracy new [Re: Moromete]
      #6135683 - 10/13/13 07:30 PM

The go-to accuracy is very similar. You just have to do a little more work to get it.

If this bothers you, get a CGEM...I don't think there is any reason to avoid them anymore, and you get the NS HC you are used to...


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Ranger Tim
scholastic sledgehammer
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Reged: 03/25/08

Loc: SE Idaho, USA
Re: Pointing accuracy new [Re: rmollise]
      #6136131 - 10/14/13 12:09 AM Attachment (5 downloads)

Here is M1 after using Gemini 1 with a GM-8 to slew. The field of view is around a degree across the widest point. I used a DSLR LCD with the view magnified 10X to center the alignment stars when calibrating the goto. I never bother swapping out for an eyepiece anymore while imaging. My Sphinx also has at least this much accuracy. I have used my buddy's Atlas a time or two and it runs equally as well. What's usually the problem? Inattention to procedure and not having the star names handy is really the only reason for me to fail. I rarely ever have to move the scope to center objects for framing unless they are filling the frame and I need all the space I can get.

Go-to is a wonderful thing. I have learned more since I got it than I ever thought I would. Sure beats the day when I use to spend a half hour finding a faint fuzzy. Now I get to learn where they hide and see more of them to boot!


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Moromete
professor emeritus


Reged: 02/15/12

Loc: Romania
Re: Pointing accuracy new [Re: Ranger Tim]
      #6136282 - 10/14/13 04:42 AM

Off-topic: Can one lower the speed of onscreen text on Syncan HC to read it easily in winter nights, as is possible with Celestron Nexstar HC?

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Raginar
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Reged: 10/19/10

Loc: Rapid CIty, SD
Re: Pointing accuracy new [Re: Moromete]
      #6136589 - 10/14/13 10:30 AM

Tim, that's beautiful. I started plate solving my images and haven't had an issue with pointing ever since. You can plate solve with a mallincam cam but stealing a screen capture. Rene over at Gemini2 says it's just not realistic to get a good alignment with only 2 stars... I trust his math

Completely off topic. Sorry.


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