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Guiding Problem?

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#1 Stew57



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Posted 21 October 2012 - 05:14 PM

I have been guiding my CGEM C11 with the celestron guidescope 80mm F7.5. The DEC is very good but I do get some elongation in the RA axis.

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The graphs are pretty much the same for all runs. There is always a spike at the same place in the frequency spread. it appears at the 8/3 pe error location, the rest of the errors are random and change between imaging runs. Is this because the 8/3 PE error of my mount (runs about 75% of the worm PE) is too hard to guide out?

I am using my setup for live video work and have just started guiding. The mount cannot be used for longer integrations without guiding.

#2 orlyandico


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Posted 21 October 2012 - 10:45 PM

hi Mark

Looking at your guiding graph that's about +/- 0.8" - or is that +/- 0.8 pixels?

If it's already in arc-seconds, then you aren't gonna get any better than that.

I bet your RMS is less than that, maybe 0.4" ?

That sort of performance is as good as it's going to get. I think guiding a C11 tightly on a CGEM is... not really doable. Try using a reducer..

Alternatively, try an OAG. Might help. Tighter guiding intervals too. Metaguide? Frank says sub 1" is consistently possible with MG on CGE-class mounts.

#3 orlyandico


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Posted 22 October 2012 - 11:11 AM

Hi Mark,

Post my miraculous CGEM resurrection, here is a guiding graph I took (the guider is a 50mm guidescope). But you can see my residual PE and the largest is also the 8/3. Interesting that the fundamental is so tiny it's lost in the noise. But then I have an Aeroquest worm.

Posted Image

#4 orion69


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Posted 22 October 2012 - 01:06 PM

If you manage to get decent images with C11, then you have really exceptional CGEM mount.
But I don't think you can manage that without OAG (flexure).


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