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Old 11-09-2016, 07:56 PM
Zuts
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Guiding Question

Hi,

I used to image with a TV 85 @ 0.8x. For guiding I used a 102mm f5 guide scope.

I now have an Edge HD 9.25 and wish to try some F10 imaging. Based on the assumption that it is best to guide as close to the imaging F ratio as possible I don't think the 102mm refractor will cut it.

Would I be better off trying to guide through a Celestron C6. Once I get a reducer for the Edge then a C6 would nearly have the same FL. The C6 would also serve dual duties on a EEA setup with an Atik infinity and a 0.5 reducer.

I would piggy-back the C6 on the Edge mounted on a AZ-EQ6 mount.

Any thoughts appreciated

Cheers
Paul
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  #2  
Old 11-09-2016, 08:48 PM
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Manav (Yugant)
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Is OAG an option
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Old 11-09-2016, 09:03 PM
Zuts
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Originally Posted by Manav View Post
Is OAG an option
Possibly, but I've never done it before and am more familiar with a seperate guide scope. The camera would be an SBIG ST2000 color, guiding through a ZWO ASI290MC.

Cheers
Paul
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Old 11-09-2016, 09:16 PM
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Atmos (Colin)
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If you're guiding through a guide scope you don't need to match the F/Ratios. The guiding software does a really good job at keeping stars within a fraction of a pixel so your 102 F/5 should do fine.

One issue you are likely to come up against is a difference in flexure and mirror slop between the guide scope and the Edge 9.25. Both telescopes cool and flex at different rates and presumably in different directions. Your SCT is also likely to suffer from some mirror slop to some degree.

What this means is that your guide scope can do a great job and keeping its star from moving and you can get a great guiding RMS but still get star trailing. This is where an OAG comes in handy as it keeps guiding with the flexure of your Edge 9.25.

To answer your question, you can guide with your 102 F/5 but there is a chance you may run into issues with longer exposures. Only one way to find out though
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Old 11-09-2016, 09:22 PM
Zuts
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Quote:
Originally Posted by Atmos View Post
If you're guiding through a guide scope you don't need to match the F/Ratios. The guiding software does a really good job at keeping stars within a fraction of a pixel so your 102 F/5 should do fine.

One issue you are likely to come up against is a difference in flexure and mirror slop between the guide scope and the Edge 9.25. Both telescopes cool and flex at different rates and presumably in different directions. Your SCT is also likely to suffer from some mirror slop to some degree.

What this means is that your guide scope can do a great job and keeping its star from moving and you can get a great guiding RMS but still get star trailing. This is where an OAG comes in handy as it keeps guiding with the flexure of your Edge 9.25.

To answer your question, you can guide with your 102 F/5 but there is a chance you may run into issues with longer exposures. Only one way to find out though
Thanks for the reply.

The Edge has mirror locks so hopefully there wont be much mirror slop. Will piggybacking the guide scope reduce differential flexure?

Also, I am thinking of selling the 102 F/5 to part fund a C6 for EEA with an Atik infinity. Is it difficult to guide through the C6 given the long FL, I could put a reducer on it?

Cheers
Paul
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  #6  
Old 13-09-2016, 08:58 AM
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blink138 (Pat)
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i had the same frac as a guidescope with my reduced c11 and could easily get 3 minutes, it should be worth a go, you may be surprised!
pat
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