Setting up a dual imaging rig...... some thoughts.

[gnomus]

1 hour ago, swag72 said:

I have to say that when you get this dual rig malarky working it is just sublime  

That's as maybe but in the cloudy Midlands 2 x 0 is still 0.

[swag72]

Just now, gnomus said:

That's as maybe but in the cloudy Midlands 2 x 0 is still 0.

Yes, but when you have a 2 hour clear spell ............... That's 4  

[Gina]

And now I have the ZWO ASI1600MM-Cool and use subs of less than a minute exposure I can make use of any gap in the clouds of a minute or so   I just might go for a dual or triple imaging rig using the same cameras later on   Great thing about these cameras is that they don't need guiding

[swag72]

10 hours ago, Gina said:

And now I have the ZWO ASI1600MM-Cool and use subs of less than a minute exposure I can make use of any gap in the clouds of a minute or so   I just might go for a dual or triple imaging rig using the same cameras later on   Great thing about these cameras is that they don't need guiding

While I watch those camera's with mild interest, my desires certainly aren't piqued at this time. Guiding is easy enough (when it works!! LOL!) ...... I would consider it more when the main stream manufacturers come on line with it such as QSI. Also, I'm not sure that my little FSQ85 could cover the imaging circle sufficiently  That's what I'm telling myself as I have some other things I want to purchase  

[ollypenrice]

Good post, Sara. I'm mighty relieved that the clamshells were to blame, having suggested that they might be! It would have been embarrassing had the investment been unnecessary... 

Some more dual rig thoughts...

Our dual rig experiences largely mirror your own. You do need a tilt pan adjuster and it's good to know that the JTD does work. We have a Cassady but they are out of production, are very heavy and were very expensive. I suppose there is an alternative to the tilt pan in that you could use one scope-camera with a slightly larger FOV than the other, imperfectly aligned, and crop accordingly, but it is so much better just to have the same setups nicely aligned.

Purely through historical chance we have an SXVH36 on one side of ours and an Atik 11000 on the other. The cameras belong to Yves and Tom. The chip sizes are identical but the more expensive SXVH36 has smaller pixels. It therefore makes sense to shoot L through that and resize the Atik RGB data to match it. Anyone setting up a dual rig from scratch might consider the possibility of using cameras with the same chip size but different pixel size. For example, Moravian do the full frame Kodak with 7.3 micron and 9 micron pixels. The cost in terms of quality would be minimal if you shot RGB and OIII in the larger pixels and Lum and Ha in the small ones. Equally at short FL you could use, say, an Atik 490 for L and a 460 for RGB. The deeper wells of the 460 might help star colour while the greater resolution of the 490 would be good for L.  So, just a thought, but both cameras need not be identical but might be selected for what they can bring to the rig as a whole.

We run in two PCs because I'm easily confused... 

I believe the combination of two cameras' data is good for S/N ratio on occasions when we run the same filters in both. An imager on the French forum took the opposite view, that 5 hrs from camera A blended with 5 hours from camera B are not equivalent to 10 hours from either A or B. I think the opposite, that the residual noise is different in each and blending helps reduce it. I wonder what others think?

Yves and I have reason to doubt the practicality of using reflectors on a dual rig. We tried, repeatedly failed, investigated on the net and found other tales of failure. Maybe mirror movement is the fatal flaw. Anyone thinking of dual reflectors should be aware that the failure rate is high! That doesn't make it impossible though.

Your term 'bliss' hits the nail on the head. A working dual rig is a dream. You have the simplicity, reliability and image quality of a refractor and the speed of a fast astrograph. Give me the dual rig any day. As a provider I really need stuff that 'just works' and the dual rig does that time and time again. Ours has proved as stable as a single scope over the last couple of years.

We are not yet using robotic focus but the Mesu is so stiff that we can focus one side without troubling the guide trace for the other.

Oh, and Registar. If you set up a dual rig don't hesitate, buy Registar. Co-registering and combining takes a second.

Olly

[carastro]

I hadn't considered the implications of a dual rig using reflectors or SCTs,  surely this must mean that unless orientated perfectly, the diffraction spikes won't line up.  How do you overcome that with your SCT Sara/ Olly or do you use refractors in your dual rig?  Or perhaps it might work with one scope being a refractor ? 

Carole

[swag72]

@carastro It's strictly refractors here for me Carole and Olly too.....

[Gina]

I only considered refractors too or SLR camera lenses.

2 hours ago, swag72 said:

While I watch those camera's with mild interest, my desires certainly aren't piqued at this time. Guiding is easy enough (when it works!! LOL!) ...... I would consider it more when the main stream manufacturers come on line with it such as QSI. Also, I'm not sure that my little FSQ85 could cover the imaging circle sufficiently  That's what I'm telling myself as I have some other things I want to purchase  

I don't understand what you're saying Sara.  The ASI1600MM-Cool has a smaller sensor than the cameras you use meaning that I can use 1.25" filters without vignetting.

[RichLD]

Thank you very much for your detailed and highly informative OP Sara! I'm playing around with a dual imaging rig ATM and although it's only a widefield mono/osc combo using camera lenses and therefore no where near as complex as your setup a lot of the principles remain. Top stuff! 

[swag72]

13 minutes ago, Gina said:

I only considered refractors too or SLR camera lenses.

I don't understand what you're saying Sara.  The ASI1600MM-Cool has a smaller sensor than the cameras you use meaning that I can use 1.25" filters without vignetting.

I thought that the ASI1600 had a larger sensor than the KAF8300?.......Also, I do not have PC power to deal with the file sizes..... I am happy as I am for now

[carastro]

Quote

@carastro It's strictly refractors here for me Carole and Olly too..... 

That does make sense Sara.   I guess one could get away with one of the scopes being a reflector, but not both.  

I was fiddling with my Smartphone when I replied to your post and couldn't get back to the equipment you posted and then review what sort of scopes they were.  But I thought it was worth asking the question in case any-one had any thoughts on the matter.  

Carole 

[ollypenrice]

1 hour ago, carastro said:

That does make sense Sara.   I guess one could get away with one of the scopes being a reflector, but not both.  

I was fiddling with my Smartphone when I replied to your post and couldn't get back to the equipment you posted and then review what sort of scopes they were.  But I thought it was worth asking the question in case any-one had any thoughts on the matter.  

Carole 

The diff spikes could be lined up by rotating the tubes but mirror movement is the killer. You can only correct the guiding for one moving mirror, not even one moving mirror and one refractor.

Olly

[Davey-T]

40 minutes ago, ollypenrice said:

The diff spikes could be lined up by rotting the tubes but mirror movement is the killer. You can only correct the guiding for one moving mirror, not even one moving mirror and one refractor.

Olly

Just started on my dual / triple imaging setup this morning and " unguided " how do you think that affects the whole equation ?

Only refractors

Dave

 

[cfpendock]

This is a very interesting post.  But I don't understand why you only have two scopes.  Surely four would enable you to take LRGB together?  Or even six to include Ha and OIII..  Or would that be greedy?

Chris

[Uranium235]

Great post Sara... kinda makes me miss my old dual shooter a bit. The only thing I sometimes had issues with is keeping up with the amount of data generated (it can back up quite quickly), I was on wireless back then and it was an awful transfer rate - but no such problems now im on powerline networking. Oh, and remembering what subs have come from which camera (especially if identical) - I got into a bit of a pickle on a couple of occasions...lol.

[Davey-T]

40 minutes ago, cfpendock said:

would that be greedy?

Chris

Be damned expensive 

Dave

[michaelmorris]

20 minutes ago, Uranium235 said:

Great post Sara... kinda makes me miss my old dual shooter a bit. The only thing I sometimes had issues with is keeping up with the amount of data generated (it can back up quite quickly), I was on wireless back then and it was an awful transfer rate - but no such problems now im on powerline networking. Oh, and remembering what subs have come from which camera (especially if identical) - I got into a bit of a pickle on a couple of occasions...lol.

APT image capture software has a function that will place images from different cameras on a dual rig in different folders and if you want name the files differently as well.  As a bonus, it will co-ordinate dithering on a dual scope rig.

[michaelmorris]

1 hour ago, Davey-T said:

Just started on my dual / triple imaging setup this morning and " unguided " how do you think that affects the whole equation ?

Only refractors

Dave

 

What scopes are you planning to use on this rig?

[Gina]

I thought a triple rig was enough

I am wondering about a dual rig possibility for some time in the future (if I live that long ).  Could have two ASI1600MM-Cool cameras with two ZWO EFW filter wheels.  Currently I'm imaging with a single rig with Ha 3nm, Ha 5nm, OIII, SII and L filters.  For LRGB I change filters to HaLRGB.  The newer 7/8 hole ZWO EFW wasn't out when I started with the ZWO camera and I might get that first.  

With a dual rig a suitable mix of filters between the two needs a bit of thought.  Let's see...  Ha 3nm, OIII, L, R, ? in one and Ha 5nm, SII, G, B, ? in the other.  OR Ha3, SII, L, R and Ha5, OIII, G, B. 

Anyway, I have plenty to do with a single rig ATM.  Grabbing all possible imaging time may not be the be-all and end-all.  I first need to get the single imaging rig working reliably first.

[Davey-T]

11 minutes ago, michaelmorris said:

What scopes are you planning to use on this rig?

WO110FLT and WO Star71 to start with, need to save up for more scopes, possibly another 70ish doublet for NB.

Theoretically I can just mount a single NB filter and camera so no need for filter wheels.

Dave

[swag72]

2 hours ago, cfpendock said:

This is a very interesting post.  But I don't understand why you only have two scopes.  Surely four would enable you to take LRGB together?  Or even six to include Ha and OIII..  Or would that be greedy?

Chris

Oh my Goodness - I can't imagine my husbands face if I told him I needed another 2xFSQ85, another 2xKAF8300 sensors and the Astrodon filters to match. I told him they were only £50  

[ollypenrice]

3 hours ago, Davey-T said:

Just started on my dual / triple imaging setup this morning and " unguided " how do you think that affects the whole equation ?

Only refractors

Dave

 

I can't see anything wrong in principle. Don't expect your scopes to line up, though, without a tilt pan adjuster. On the other hand the one with the wider FOV might well provide complete coverage of the image from the one with the longer FL.

Looks good!

In tidying up today I found a big Cassady triple bar. Tom already has a secod Tak 106. We have three full frame cameras avaialble. Noooooooooooooooo!!!! 

It's interesting to note that, by definition, a second scope is worth one F stop in equivalence.

Olly

 

[Davey-T]

35 minutes ago, ollypenrice said:

I can't see anything wrong in principle. Don't expect your scopes to line up, though, without a tilt pan adjuster. On the other hand the one with the wider FOV might well provide complete coverage of the image from the one with the longer FL.

Olly

 

 

Got two scopes mounted and balanced, I've fitted 15mm aluminium plates between the clamps and the bar and I'm hoping to make some adjustment in them to align the scopes to save on weight and expense of adjustable mounts,

I can use Maxim to align them next full Moon

Only embarking on this project as it's taken weeks to gather enough subs for a decent image and most things disappear for months before I gather enough.

Dave

 

 

[carastro]

This is my annotated dual rig (from my website).  This is the set up I take to astro-camp (except when at camp I put it on an HEQ5).  

 

[iapa]

23 hours ago, cfpendock said:

This is a very interesting post.  But I don't understand why you only have two scopes.  Surely four would enable you to take LRGB together?  Or even six to include Ha and OIII..  Or would that be greedy?

Chris

I would imagine that the mount capabilities would be severely stretched for most? The Equinox ED80 comes in around 12lbs - four of them with cameras and mount plates (1 lb seems a reasonable estimate for each for each ),  so we are in the realm of the 100+ lb payload rated mounts.

I imagine that trying to line it all up would be a 12 month project; certainly where I am with very poor skies.

Too rich for my pocket anyway.