Dual imaging rig

huerbsch
23 Apr, 2018 21:13
Espirit 100 f/5.5 + Cooled Canon 6D = 2.44" per pixel
WO GT71 f/4.7 + QHY163m = 2.33" per pixel

I already have an ADM side by side saddle, would just need to get another stepper motor to be able to auto-focus both focusers. For those who have done this… what are the top issues/pitfalls encountered? My subs would only be ~ 3 min so hopefully not long enough for flexure to mess things up. Would piggy back a ZWO 60mm guide scope ontop of the GT71 to help counterbalance the beefier Espirit 100 which is around 16lb.

Mount is a DarkFrame tuned NEQ6-Pro thats pier mounted.
huerbsch
24 Apr, 2018 12:48

huerbsch
24 Apr, 2018 12:50
Ill use SGP to rotate both cameras, but if they are not exactly aligned/pointing the same, is the only problem having to crop?
MikeP
24 Apr, 2018 18:04
Hi Robert,

I have a similar setup with an FSQ and a WO71 on a side by side saddle. I find balance is not a problem, on the contrary it almost seems easier as you can move sideways and for and aft to achieve balance all round. To help I did come up with a fine tuning mechanism in both axis , as especially laterally it's a bit of a pain to shift the whole setup. Laterally I achieved this by using a small clamp at the bottom of the saddle plate which can be moved and for fore and aft fine tuning I just move the guide scope in it's rings. Once you have balance it's worth marking the positions for future use as this cuts down the next setup considerably.

Achieving a similar field of view might be difficult if you don't have an adjustable saddle plate of some description. I tried it and it didn't work for me. In the end I got an Avalon X-Guider (it can take 5kg) which is really light and works for the WO71. It's quite expensive though and there are other beefier options out there for similar money so if mount load is not an issue they might be better.

I also have auto focus running on both scopes. Initially I was using an off-axis guider but this didn't work well as guiding is all over the place when focusing that scope which then affects subs from the other scope (and unfortunately there is no synchronisation in SGP - yet). So I went with a guide scope instead and now each scope does it's own thing and I only really loose subs during the flip.

Hope this helps!
Edited 24 Apr, 2018 18:09
huerbsch
25 Apr, 2018 15:57
thanks! thats the type of feedback I was looking for.
gnomus
25 Apr, 2018 20:59
I struggle to get my head around the geometry.  For example, some folks with only one scope on top of a mount get concerned about cone error.  With a side-by-side dual rig it strikes me that you have both scopes hanging out to the side of the mount.  One will be parallel (within the tolerances of the plates and saddles) to the main mount axis.  The other scope will be ‘toed in’ to a lesser or greater extent.  What effect (if any) does all of this have on the final result?  I don’t know, but I am hoping that someone will.
MikeP
26 Apr, 2018 07:00
Hi Steve,

I'm no expert and don't really know the theory behind it all but practically I've not had any noticeable problems imaging around 400mm focal length. From what I have gathered of others, cone error only really affect the pointing accuracy and not really tracking and it's flexture and field rotation can can cause bigger problems with a dual scope setup. There is an interesting article from Peter Rejto and his woes of trying to sort out problems with his dual rig including a Tec140 and a Tec180:

https://astronomytechnologytoday.com/2017/05/29/a-practical-automated-multi-camera-astro-imaging-system-design-one-mount-one-computer-two-imaging-cameras/
gnomus
26 Apr, 2018 07:07
Michael Poelzl
Hi Steve,I'm no expert and don't really know the theory behind it all but practically I've not had any noticeable problems imaging around 400mm focal length. From what I have gathered of others, cone error only really affect the pointing accuracy and not really tracking and it's flexture and field rotation can can cause bigger problems with a dual scope setup. There is an interesting article from Peter Rejto and his woes of trying to sort out problems with his dual rig including a Tec140 and a Tec180:

https://astronomytechnologytoday.com/2017/05/29/a-practical-automated-multi-camera-astro-imaging-system-design-one-mount-one-computer-two-imaging-cameras/

Thanks Michael.  I'll take a read of that article.
huerbsch
26 Apr, 2018 17:23
Sara W also has a nice write up on a dual side by side setup with 2 baby Q’s

dual FSQ85’s
Edited 26 Apr, 2018 17:28
 
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