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Equipment Discussions >> Mounts

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powerstroke01
sage

Reged: 06/19/07

Loc: Western Sierra Nevada Foothill...

About to trash my whole setup.
#5427176 - 09/18/12 11:31 AM

Im so frustrated, i just dont know what to do.
Im getting oblong stars. They all are oblong in the RA direction.
Im using a Losmandy G11, with an 10"lx200. Permanently mounted in my obs.. Even with autoguiding i can not get round stars.
Ive polar aligned and realigned. Ive collimated over and over again. Ive checked that the gears are meshed correctly. I even have the ovision worm. I have cleaned the main gear and worm and relubed.. And my pe is somewhere in the 7 range consistantly.
Ive used mirror lockup in the dslr. Ive reset the mount. Ive done everything i can think of and im sure im missing some things that i havent listed here.

This is soo frustrating because just 1year ago i could get round stars in a 10minute unguided exposure.

Post Extras:

Peter in Reno
Post Laureate

Reged: 07/15/08

Loc: Reno, NV

Re: About to trash my whole setup. new

[Re: powerstroke01]
#5427187 - 09/18/12 11:37 AM

If you are using guide scope, have you considered OAG? You'll be surprised of the results. I was getting exactly the same thing with a guide scope guiding an SCT until I threw away the guide scope and replaced it with OAG and Lodestar.

Peter

Post Extras:

powerstroke01
sage

Reged: 06/19/07

Loc: Western Sierra Nevada Foothill...

Re: About to trash my whole setup. new

[Re: Peter in Reno]
#5427189 - 09/18/12 11:39 AM

No, not really. Ill have to do some reading.

Post Extras:

EFT
Vendor - Deep Space Products

Reged: 05/07/07

Loc: Phoenix, AZ

Re: About to trash my whole setup. new

[Re: powerstroke01]
#5427190 - 09/18/12 11:39 AM

What have you done to start eliminating the possible sources of the problem?

Do you have a smaller scope that you could try out, like maybe a refractor, so see if the problem is in the scope, dovetail, etc.?

Narrowing things down to the mount or the scope/imaging train will probably help.

Post Extras:

D_talley
Carpal Tunnel

Reged: 07/07/05

Loc: Richmond VA

Re: About to trash my whole setup. new

[Re: powerstroke01]
#5427191 - 09/18/12 11:39 AM

Have you locked the mirror on the scope, if that is possible?

Also, what happened in the past year that could affect the mount's performance. When did the O-worm get installed?

The fact that images are showing oblong stars even when guiding points me to the main scope mirror shifting or the guider mount shifting.

Post Extras:

powerstroke01
sage

Reged: 06/19/07

Loc: Western Sierra Nevada Foothill...

Re: About to trash my whole setup. new

[Re: EFT]
#5427214 - 09/18/12 11:50 AM

Quote:

What have you done to start eliminating the possible sources of the problem?

Do you have a smaller scope that you could try out, like maybe a refractor, so see if the problem is in the scope, dovetail, etc.?

Narrowing things down to the mount or the scope/imaging train will probably help.

I dont have any other scopes to try. How else can i narrow it down?

Post Extras:

powerstroke01
sage

Reged: 06/19/07

Loc: Western Sierra Nevada Foothill...

Re: About to trash my whole setup. new

[Re: D_talley]
#5427223 - 09/18/12 11:55 AM

Quote:

Have you locked the mirror on the scope, if that is possible?

Also, what happened in the past year that could affect the mount's performance. When did the O-worm get installed?

The fact that images are showing oblong stars even when guiding points me to the main scope mirror shifting or the guider mount shifting.

I have not tried locking the mirror. Not sure its possible now that i think about it though.

The o-worm has been on the mount since i bought it.

I wonder if youre right about the mirror shifting. But the stars are oblong even in short exposures. Say of about a minute or so. And whats strange is that they dont seem to really get worse in longer exposures.. Maybe something in the camera????

Post Extras:

Stew57
Carpal Tunnel

Reged: 05/03/09

Loc: Silsbee Texas

Re: About to trash my whole setup. new

[Re: powerstroke01]
#5427235 - 09/18/12 12:00 PM

Try rotating the camera 90 degrees. See if the direction of star elongation moves with the camera or is in the same orientation you have now.

Post Extras:

EFT
Vendor - Deep Space Products

Reged: 05/07/07

Loc: Phoenix, AZ

Re: About to trash my whole setup. new

[Re: powerstroke01]
#5427239 - 09/18/12 12:03 PM

Quote:

Quote:

What have you done to start eliminating the possible sources of the problem?

Do you have a smaller scope that you could try out, like maybe a refractor, so see if the problem is in the scope, dovetail, etc.?

Narrowing things down to the mount or the scope/imaging train will probably help.

I dont have any other scopes to try. How else can i narrow it down?

That is going to make things tough. I suspect the problem is in the scope/imaging train and is most likely due to flexture. However, the new worm could be the issue as well.

If you upgraded to the new worm yourself, then you could put the old one back in and see what that does so that you can eliminate or verify that the new worm is the problem.

Post Extras:

powerstroke01
sage

Reged: 06/19/07

Loc: Western Sierra Nevada Foothill...

Re: About to trash my whole setup. new

[Re: Stew57]
#5427240 - 09/18/12 12:03 PM

Why didnt i think of that. haha I must try that tonight.

Thanks!

Post Extras:

powerstroke01
sage

Reged: 06/19/07

Loc: Western Sierra Nevada Foothill...

Re: About to trash my whole setup. new

[Re: EFT]
#5427250 - 09/18/12 12:08 PM

Quote:

Quote:

Quote:

What have you done to start eliminating the possible sources of the problem?

Do you have a smaller scope that you could try out, like maybe a refractor, so see if the problem is in the scope, dovetail, etc.?

Narrowing things down to the mount or the scope/imaging train will probably help.

I dont have any other scopes to try. How else can i narrow it down?

That is going to make things tough. I suspect the problem is in the scope/imaging train and is most likely due to flexture. However, the new worm could be the issue as well.

If you upgraded to the new worm yourself, then you could put the old one back in and see what that does so that you can eliminate or verify that the new worm is the problem.

I doubt the worm is the issue. Ive had very good success with it in the past. So had the previous owner.. So i could try the old worm...

Should i take the scope and everything off the mount, reasemble everything so make sure everything is tight?
I just dont get how i used to get good images and now i get movement...

Post Extras:

powerstroke01
sage

Reged: 06/19/07

Loc: Western Sierra Nevada Foothill...

Re: About to trash my whole setup. new

[Re: powerstroke01]
#5427255 - 09/18/12 12:10 PM

Actually i think you guys are right about flexure. Due to the fact i have a hard time getting good GOTO's..

Post Extras:

tjugo
professor emeritus

Reged: 11/06/07

Re: About to trash my whole setup. new

[Re: powerstroke01]
#5427285 - 09/18/12 12:25 PM

Hi,

I was debugging a similar issue with my setup, Atlas + Epsilon 160 + short guidescope. The guide graph looked very flat but I was getting elongated stars mostly in the RA axis.

I tried everything, change guiding params, switch back and forth from maxim to PHD, change guide scope, drift alignment, PEC etc etc....

Long story short, the problem was some small amount mirror shift, usually mirror shift produces double stars but in my case it was producing elongated stars. I put together my old OAG and the stars are round and small again.

Some people suggested that the issue was focuser flex , probably, but the OAG took care of the problem.

Cheers,

Jose

Edited by tjugo (09/18/12 12:28 PM)

Post Extras:

freestar8n
Carpal Tunnel

Reged: 10/12/07

Re: About to trash my whole setup. new

[Re: powerstroke01]
#5427456 - 09/18/12 01:43 PM

Quote:

Im so frustrated, i just dont know what to do.

OAG

Frank

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Jared
Post Laureate

Reged: 10/11/05

Loc: Piedmont, California, U.S.

Re: About to trash my whole setup. new

[Re: powerstroke01]
#5427642 - 09/18/12 03:31 PM

If you look at your guide results are they good? Based on the log, what is the RMS guide error? Do the RA and DEC numbers look similar?

If the guider is reporting good results, but you still have elongation in your stars you are likely looking at differential flexure and/or mirror flop. Frankly, that's to be expected using a guide scope with an SCT--especially one with no mirror locks. The only thing that makes me at all suspicious is the fact that your error was in RA. With differential flexure, the direction of the elongation will vary with the object.

Basically, with a 10" SCT used at Cassegrain focus (even with a reducer) you are likely to get better results with an OAG. The only downside is that it can be hard finding a guide star. That and the fact that you'd have to buy a guider.

Post Extras:

powerstroke01
sage

Reged: 06/19/07

Loc: Western Sierra Nevada Foothill...

Re: About to trash my whole setup. new

[Re: Jared]
#5427661 - 09/18/12 03:39 PM

Thanks all! Im going to try a few new things tonight. Also ordered an OAG.. We will see how it works tomorow night.

Post Extras:

Peter in Reno
Post Laureate

Reged: 07/15/08

Loc: Reno, NV

Re: About to trash my whole setup. new

[Re: powerstroke01]
#5427683 - 09/18/12 03:52 PM

Which brand OAG did you get? What brand autoguider are you using?

Peter

Post Extras:

brokenwave
super member

Reged: 05/10/11

Loc: Scottsdale, AZ

Re: About to trash my whole setup. new

[Re: powerstroke01]
#5427694 - 09/18/12 03:57 PM

Are you using a remote cable or program to trip shutter? and if you don't have a 5-10 delay after mirror flips up you are probably getting bounce somewhere. Try this:
If your exposures are short say 10 sec. or less. You might be getting bounce from the camera shutter. Try increasing your exposures by 5 seconds or so and use a dark piece of cardboard to block the front of the tube for that 5 seconds,
without touching the tube with it.
That will let what ever is bouncing settle down without the camera being exposed to what you are photographing. It will take that out of the problem solving if it isn't tracking error. Since you longer exposures are the same as short ones it sounds like something isn't totally locked.

Post Extras:

Alterf
sage

Reged: 04/07/06

Re: About to trash my whole setup. new

[Re: brokenwave]
#5428024 - 09/18/12 06:36 PM

A friend had a similar problem and found that there was play in the RA. Adjusting the RA backlash and tightening things down cured it. I hope you can find the source of the problem. Nothing is more frustrating.

Val

Post Extras:

powerstroke01
sage

Reged: 06/19/07

Loc: Western Sierra Nevada Foothill...

Re: About to trash my whole setup. new

[Re: Alterf]
#5428518 - 09/19/12 12:27 AM

Im bummed. Im out in the obs right now and im seeing huge jumps in the RA...
Its def in the mount and not the camera.
Today i took everything off the pier and started over.
I even left off the spotting scope and the guide setup to save a bit of weight.

Post Extras:

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