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Old 11-03-2014, 04:25 PM
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PRejto (Peter)
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Imaging from 2 scopes at same time?

Well, a bug got planted in my head by a certain well known imager here. Not sure if he was joking or not(!!),but I posted a picture of my MEII with a TEC140 mounted to the rings of my new TEC180. This certain "firebrand" suggested that I ought to capture luminance with one scope and colour with the other. Now, of course, I have enough trouble running one scope but running two simultaneously seems like a big ask. But, the idea is festering as they do and I'm looking for a good excuse to hold onto the TEC140. So.....

A few calculations.

TEC180 with G2-8300 CCD = .88 arc-sec FOV ~ 37x49 arc-min
TEC180 with Trius = .74 arc-sec FOV ~ 27x34 arc-min
TEC180 Theoretical resolution = .66 arc-sec

TEC140 with G2-8300 = 1.14 arc-sec FOV ~ 48x63 arc-min
TEC140 with Trius = .95 arc-sec FOV ~ 35x43 arc-min
TEC140 Theoretical resolution = .8 arc-sec

It would seem that the TEC180/G2-8300 and TEC140/Trius combination give a very close match in FOV and resolution. I think my inclination would be to run the TEC140/Trius for colour and the TEC180/G2-8300 for luminance. My reasoning would be that the Trius sensitivity might grab the colour more easily, and the TEC180 (and higher resolution) would be good for luminance. Hopefully the increased aperture but less sensitive camera would work well. On the other hand, it also comes to mind that not matching the FOV could provide for a nice wide-field view from the TEC140 (colour) and luminance data on the object of interest. I'm just not sure at all about the technique of combining stacks that are at differing resolutions. I know that CCDStack will combine 1x1 with 2x2. Will it also do intermediate values?

The next issue would be whether there is any hope of accurate guiding of both scopes with one piggybacked on top of the other. Is it worth trying, or is it a hopeless combination in terms of flexure? Would side by side mounting be better or also problematic? I also imagine getting both scopes pointing exactly so the target is centred in both to be difficult. Would this be done with shims?

Then there would be issues re running two focusers, two cameras, etc etc.

Hopeless? Insanity? I'm intrigued by anything that might take greater advantage of the limited nights of good seeing in Sydney!

I'd appreciate some input here as I'm off to the USA for 2 weeks. If I need certain gear to pull this off I could bring it back with me hopefully. I'm bringing my TEC Focuser off the 180 to have a custom motor fitted at Starizona, and while I'm gone a machine shop is drilling out my MX weights so they will fit on the MEII shaft.

Thanks,

Peter
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  #2  
Old 11-03-2014, 04:32 PM
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pvelez (Pete)
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Have a good trip Peter

Pete
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  #3  
Old 11-03-2014, 06:42 PM
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Sounds like voodoo to me. Good luck with that.
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Old 11-03-2014, 08:18 PM
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Joshua Bunn (Joshua)
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In terms of flexure, i would do a side by side combo rather than piggybacking - its far better. Safe travels Peter.

Josh

Last edited by Joshua Bunn; 11-03-2014 at 09:40 PM.
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Old 11-03-2014, 08:40 PM
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Firebrand??? well, IIII never ...some people are just too serious on here that's all .

Yes, I (of course ) think it is a great Idea and really, I think any of those combinations could work

I would mount the scopes on top of each other myself with solid hard connections spaced as wide as possible along the respective OTA's to minimise diff flex with the guiding.

If the FOV's don't match perfectly it doesn't matter, co registering the resulting finished RGB to the high res Lum and doing an LRGB combine will work perfectly, I do it all the time.

Awesome approach and I will look on with much interest should you go dwn this route.

Have a nice holiday...you communist, TEC loving, mexican gunslinger... that too militant speak for ya

Mike
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Old 11-03-2014, 09:01 PM
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I have thought of doing similar at times. Tom Davis used to do this a lot and to great effect.

I would do it the other way round though. The TEC/Trius for max resolution (Trius has smaller pixels - unless you get bloated bright stars like I do - I'd love to find out if you do too, if not it would point the finger at the CCD reflection coatings).

Colour does not need as high rez.

As pointed out the challenge may be flexure.

Greg.
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Old 11-03-2014, 09:13 PM
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Thanks guys! I guess I will give this a go when I get back. Of course I still need to polar align the mount and do PEC, but hopefully a few clear nights and all that will get sorted. I'm just assuming that all the issues I had with the MX couldn't possibly exist in this new mount....

Oh, I see my provocations have tickled the tiger in Mr. Sidonio! I agree with everything he said except being a communist and Mexican gunslinger.

Pedro
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Old 11-03-2014, 09:44 PM
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Quote:
Originally Posted by PRejto View Post

Oh, I see my provocations have tickled the tiger in Mr. Sidonio! I agree with everything he said except being a communist and Mexican gunslinger.

Pedro
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Old 12-03-2014, 07:09 AM
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Certainly an idea worth investigating. Minimising flexure will be your only really issue. You will need to run two computers too for capture. It will be simpler that way. If you OAG with the longer focal length system and the other system just captures this will help with star shapes.

It will certainly mean you can devote one scope purely to the capture of luminance on any given night. With 4 nights of capture you could quarter the capture time if you want to maximise mega data collection.
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Old 12-03-2014, 07:58 AM
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Octane (Humayun)
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I was going to mention, Tom Davis made some extraordinary images using this technique, particularly of his VdB catalogue, hence earning him the title of dust sucker.

I can't get my head around how one would successfully win the challenge of dithering between frames with two cameras run by two machines.

Is there software on the market which will run two cameras? A little like how MaximDL can handle the STL-11000M with the internal guide camera.

Would be interested to find out.

H
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Old 12-03-2014, 08:04 AM
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multiweb (Marc)
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Quote:
Originally Posted by Octane View Post
Is there software on the market which will run two cameras? A little like how MaximDL can handle the STL-11000M with the internal guide camera.

Would be interested to find out.

H
Nebulosity 3 will support many instances of the program connecting to different cameras. I did that with a QHY9 mono shooting through a lens piggy backed on my Newtonian running the QHY8. I was guiding with PHD. I just offset the subs a couple of minutes so download would no occur at the same time but while one of the cameras was still imaging as to minimise USB traffic during readout.
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Old 12-03-2014, 08:16 AM
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I image through 2 scopes side by side all the time. My reason is different as one is for spectra and the other is for simuiltaneous photometry but the process is the same.
I guide with the off axis guider on the spectrograph as the main guider.
If I want better guiding with the scope for images, it has an ST10XME on it using an AO unit. This will guide seperately within the limits of the travel of the AO unit. This takes care of any differential flexure and I have never reached the limits of the travel of the AO unit.
I use 2 separate computers. One a very old desktop running XP and a cheap lappy for the other camera. All fit on a little table easily. I then transfer the files to an ext hard drive for processing at my leasure on a more powerful puter.
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Old 12-03-2014, 08:28 AM
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PRejto (Peter)
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What a brilliant idea to use an AO unit on one of the scopes! Certainly a way out of a problem of differential flexure on one scope. Now I can spend even more $$$$$ and have more gadgets!!

Peter
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Old 12-03-2014, 08:38 AM
WingnutR32 (Sam)
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Watching this thread closely with exciting interest! Keen to see what you come up with using the two scopes together.



Quote:
Originally Posted by strongmanmike View Post
If the FOV's don't match perfectly it doesn't matter, co registering the resulting finished RGB to the high res Lum and doing an LRGB combine will work perfectly, I do it all the time.

Awesome approach and I will look on with much interest should you go dwn this route.

Have a nice holiday...you communist, TEC loving, mexican gunslinger... that too militant speak for ya

Mike
Comedian
First off, Ha Ha Ha Ha Ha!!!

Secondly, Mike, could you elaborate on the co-registering and combine? I have tried this previously in MaximDL and I always seem to get issues with the resolution being too dramatically different (not 1x1 with 2x2, but usually 1x1 with almost something like 1.75x1.75).

Which programs have you used to successfully do the combine?

Cheers
Sam
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Old 30-03-2014, 01:39 PM
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PRejto (Peter)
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Back from the USA with a side x side solution by ADM. After a day of frustration re the vera plate and through the mount cables I finally have a balanced system. It looks like an anti-aircraft battery!

The TEC180 "unfortunately" came with the TEC focuser and not the Feather Touch. There is nothing wrong with the TEC except that there is no easy solution to motorize the focusing. I took the TEC focuser with me to Tucson. Dean - at Starizona - is making up a new model of motor housing to work with these focusers (which are quite a departure from the FT). Mine will hopefully be ready in a month or so, and then the motor will be for sale generally through Starizona. I'm also waiting on a part from Starlight for the TEC140 focuser so that I can finally eliminate all pressure fittings to the camera.

I had 2 counter weights left from my MX which I had drilled out at a local machine shop.

Now, I just need a clear night to polar align and run a pointing model, PEC , etc.

QUESTION: Since I will be running 2 cameras I've got to provide voltage to both. The ME power cable is rated for 20 volts 7.5 amps. The Trius power supply is rated 12 V 2.5 amps, and the Moravian 12 v 5 amps. Would it be a mistake to wire the 2 power supplies in parallel (12 volts, 7.5 amps?), and then split off power to each camera after it runs up to the control panel? Other options would be to buy a single larger 12 volt supply, or run a separate power lead through the mount which is my least favorite option.

Answered my own question re 2 power supplies. That won't work as it turns out the supply with even slightly higher voltage will take all the load

A bit closer but moving too slowly.

Peter
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Last edited by PRejto; 31-03-2014 at 12:23 PM.
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Old 30-03-2014, 09:04 PM
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What a beast
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