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Tandem 8" Edge setup

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#1 plane48

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Posted 05 December 2020 - 12:04 PM

This might be one of the dumbest questions ever asked here, but curious minds want to know (mine)tongue2.gif

 

My mount can easily handle the weight (1100gto), but is this a practical way to increase my imagining time?



#2 Don W

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Posted 05 December 2020 - 12:46 PM

Need more info. How do you propose to configure them?



#3 plane48

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Posted 05 December 2020 - 03:50 PM

Oops, I meant to say a side by side mounting of two EDGEHD 800's.  Identical cameras, etc.



#4 plane48

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Posted 05 December 2020 - 06:49 PM

I want to take both 8" Edges and auto guide with one of them pointing to a common target.  I know side by side refractors is quite common for this purpose but has anyone done it with a couple of C8's or larger?



#5 Don W

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Posted 05 December 2020 - 07:34 PM

All you need to autoguide is a small refractor. Why would you spend that much money on a 2nd expensive OTA?? Sorry, there's absolutely no advantage to doing that. It's expensive and not efficient.


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#6 plane48

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Posted 06 December 2020 - 01:43 AM

Thanks for the reply Don.  Let me try to clarify my reasoning a bit.  My present EDGEHD 800 is setup with a OAG so it would be the guider and imager as usual.  But I would like to be able to double my data acquisition per session.  I could take all my luminance with one scope and the other take the RGB side of things, for example.  By mounting both scopes on the mount in a side by side configuration

I think this would work out but I don't know for sure and was hoping someone in Cloudy Land had tried it.  Hope this makes sense to you.

 

Rich


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#7 luxo II

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Posted 06 December 2020 - 05:10 AM

It will work but the challenge is to accurately align the two scopes - and have them stay that way.

I’ve tried aligning my 6” and 10” maks (the 6” is piggybacked on the 10”) and it’s not trivial. Flexure does occur.

Edited by luxo II, 06 December 2020 - 05:14 AM.

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#8 plane48

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Posted 06 December 2020 - 09:08 AM

That's what I was wondering about.  The actual aiming of the second scope to match the primary scope.  Since I will be dropping the native f10 to a more reasonable f7 might help a bit.  I guess I won't know until I try it.  Right now purchasing one is 2 to 3 months out so I probably wouldn't even get  a rig like this up and running for at least 6 months.  I plan on boxing up my current scope and sending it in to Celestron for a checkup once I get the second scope.



#9 KLWalsh

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Posted 06 December 2020 - 09:58 AM

I’d use the first quarter Moon as a starting point for aligning the second scope to the first. Pick an obvious feature and use a moderately high power eyepiece to center the feature in A, then adjust scope B to align on the same feature.
I’d use an extra bar across the top of the two scopes (an X-shaped bracket would be better) so they maintain alignment as the mount tilts and turns.
A small amount of mis-alignment won’t affect the stacking of the images from the two scopes.
You might need to plate-solve the starfields from both scopes to be sure the focal lengths are identical, or nearly so.

#10 plane48

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Posted 06 December 2020 - 10:13 AM

Thanks KLWalsh for the reply.  Since I already plate solve through SGP this would work out great.  I need to go to the SGP forum and see about running two instances of SGP or maybe there is a way inside one instance.  I like the X brace bracket idea to keep both scopes locked together.



#11 reddog1972

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Posted 08 December 2020 - 05:56 PM

I've imaged side by side as well as piggybacked before on a few different systems.  The trick is to align both OTAs not only to the same exact location, but to orient the cameras identically so your FoV is virtually the same.  This reduces cropping when aligning and combining the channels between both cameras/OTAs.  The easiest way I've found to align both scopes is to do it in the daytime on an obvious target.  Identify target on the fixed OTA 1 and then dial in adjustable OTA2 (ideally you'd want this 2nd OTA mounted with adjustable rings so you can easily adjust where it's pointing).  That however may be a tad bit more difficult with a C8 than with a refractor.


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#12 N_DD

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Posted 09 December 2020 - 02:12 PM

Assuming that you can align both scopes and cameras to have matching fields of view, the OAG will compensate for the mirror flop one of the two scopes: you might end up tossing more subs from the other scope due to elongated stars.

Maybe a better alternative would be to have only one scope and use a dichroic beam splitter and two cameras to acquire simultaneously two colors (e.g. red and green, or H-alpha and OIII) but it won't give any advantage for luminance... assuming the back-focus and mechanical stability of the whole rig would be enough!!!




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