Old 04-06-2013, 06:24 PM
Hans Tucker (Hans)
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Dual Scope Imaging

Ok..how do I describe this without confusion...Any IIS's imaging the same subject/target with two scopes at the same time possibly in a tandem set up.

I was flicking through a copy of Sky at Night on the news stand today and it was describing dual scope imaging and combining the images/results.

Is there an advantage to this? Can you image with say two refractors of the same focal length but different apertures and then combine the images?
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Old 04-06-2013, 07:02 PM
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asimov (John)
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I've always wanted to do it by adding a second C11 & mount to my 'collection' but just can't afford it right now. I wanted to image the same planet at the same time with different cameras & combine the results.

Makes sense to me.
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Old 04-06-2013, 07:17 PM
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You can register 2 images at different focal lengths but the final image would be limited to the view of the smaller image.

The problem also would be how to get the 2 scopes so well aligned they are both imaging the same scene.

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Old 04-06-2013, 07:23 PM
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Geoff45 (Geoff)
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I have often thought about wide field, even a camera lens, plus narrow field to show the object's place in the overall scheme of things. Often, using goto, I may image two objects on different nights without realizing that they are within a degree or two of each other.
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Old 06-06-2013, 12:05 PM
Poita (Peter)
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Originally Posted by asimov View Post
I've always wanted to do it by adding a second C11 & mount to my 'collection' but just can't afford it right now. I wanted to image the same planet at the same time with different cameras & combine the results.

Makes sense to me.
Could you readily combine two captures from different FL scopes, like a C9.25 and a C11?
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Old 06-06-2013, 12:15 PM
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I image the same object with 2 different scopes on the 1 mount all the time. This is not for "pretty pics" though.
The VC200L has a camera taking photometry images using UBVRI filters.
The C11 has a spectrograph and I can concurently take spectra and photometry of the same target. The spectrograph has the most critical positioning though. I have to place the target on the slit of the spectrograph. The 2 scopes are well aligned and this puts the target slightly to to right of the centre of the image on the VC200L
This is fine for my purposes.
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Old 06-06-2013, 07:14 PM
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naskies (Dave)
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The advantage is that you're basically collecting more light in the same amount of time as imaging with one scope, so you theoretically end up with a better signal-to-noise ratio than with one scope.

For example, in Nick Risinger's sky survey he imaged with six Zeiss 85 mm lenses + FLI ML-8300 cameras on one mount. With only one camera/lens, it would have taken at least six times longer...


As for different focal lengths, you might combine data from two different scopes to as a way of getting both a wide field and depth in the target of interest, as with Mike & Rolf's recent collaboration:


So why don't more people do it? Lots of reasons that I can think of:

1. getting one scope with one camera imaging "perfectly" is hard enough on its own...

2. $$$ - two scopes, two cameras, two focusers, two guiders, two sets of filters, much beefier mount, etc.

3. instead of multiple smaller scopes with small chipped cameras, you'll (probably) get a better result with a single high-end scope/camera - i.e. lots of data from a blurry scope won't give you as good result as half the data from a high quality, well-corrected scope

4. more equipment = more things to go wrong during the night
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Old 07-06-2013, 11:02 AM
Poita (Peter)
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What about multiple observers synchronising their efforts.
Most planetary guys are out every night anyway, what if clumps of us co-ordinated our efforts to capture simultaneously and shared the results for processing?
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Old 08-06-2013, 11:09 AM
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strongmanmike (Michael)
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Hi Hans

This is the dream arrangement in my mind, to have a wider field scope collecting the RGB and a longer FL scope collecting the Lum/Ha would be great. LRGB style imaging is very time consuming so being able to effectively halve the total time spent would be a god send..especially when tackling say 140hrs

It's a no brainer really and combining the results from two systems is quite straight forward. It basically comes down to having the two scopes and two cameras in the first place and shooting the Luminance through the system that provides the best image scale and the RGB through the other, the RGB can be quite low resolution and still deliver superb final LRGB results

Depending on the two scopes you plan to tandem you may need to consider a beefier mount if you don't already have one though...or two separate mounts

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