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Old 09-02-2009, 12:37 PM
keppar (Graham)
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DSI vs DSLR

HI
I am currently using a Canon 40d for imaging.Would there be any benefit/improvement in purchasing a DSI pro11.If there is would mono with filter wheel be better. I'm asking this as I have seen some tutorials that suggest the software can be used to automate the Dark subtraction and stacking process. Is there an improvement in quality?
Thanks Kepp
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Old 09-02-2009, 05:36 PM
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renormalised (Carl)
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Well, for a start, your 40D has a lot more pixels than the DSI II Pro, hence a better resolution. Mono with filters/wheel would be better unless you don't want to fiddle around with these, then the OSC version would suffice. I would still use an autoguider and scope cause it's better to not trust the DSI to accurately guide and take pics as well. Drizzle is good, but I'd still use registax (or whatever you use) to stack and align your pics. Whilst the DSI is an OK little camera, I'd rather get a DMK or DBK. I would use both, the 40D and the DSI, for imaging but I'd be inclined to use the 40D mostly for imaging and the DSI for guiding.

I suppose for $599 (imager, fan/bracket, filter wheel and filters) it's worth the purchase. You won't get it for that price again.
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Old 09-02-2009, 07:07 PM
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peter_4059 (Peter)
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Kepp,

I've got a 400D and a DSI II pro (mono with filters) and they are a completely different imaging experience. The 400D is great at a dark site where light pollution doesn't impact things however at home in the suburbs the DSI can do a lot longer exposure without being overcome by light polution. The mono with filters is a lot more work to produce a colour image than one shot colour in both the imaging and post processing. There is also a big difference in the imaging chip size and hence field of view - the DSLR is a much bigger chip. The other consideration is the scope and whether you can achieve focus - typically you need to modify a Newt to achieve focus with a DSLR.

Peter
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Old 09-02-2009, 07:27 PM
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I think there are also a few other things to consider..

The Spectral response of a DSI will be better than that of the DSLR (unless you modify the DSLR) The DSI will capture Ha light a lot better than an out of the box DSLR.

Your field of view with a DSI is a lot more restricted than with a DSLR, that being said, if you had both, what you essentially have is a great wide field camera able to capture the larger extended objects like M42, M8 and M31 etc, and the DSI to capture the tiny little faint galaxies that can be very difficult to get a good image of with a bigger sensor...

My opinion, If you dont want the DSLR for normal photography as well as astrophotography, then go for the CCD... If you would like to dabble in terrestrial photography also, then go for the DSLR...

You really need to buy what is going to suit your needs best.
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Old 09-02-2009, 08:10 PM
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kinetic (Steve)
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Quote:
Originally Posted by peter_4059 View Post
The other consideration is the scope and whether you can achieve focus - typically you need to modify a Newt to achieve focus with a DSLR.

Peter
Probably have to modify the Newt to achieve focus with the DSI too.
I had to.
The typical DSI Pro II has a filter tray and nosepiece that doesn't
exactly help achieve focus easy.
Even when slimmed down and a filter wheel used as an alternative,
it still is hard getting focuser travel on an off the shelf Newt.
This is what I did:
http://mywebsite.bigpond.com/astrost...ter_wheel.html

If you are serious about imaging you would be aware of this problem
and the obvious solution.....people either fit a low profile focuser and/or
cut 50mm off the bottom end of the tube!. I did the 50mm cut.
I know it sounds extreme but it does the job and then you have
the freedom to focus with lots of DSLR/barlow/Eyepiece projection
or DSI Prime focus options.
You only need to add a 50mm extension tube to the focuser if you suddenly
think you 'need those 50mm back again'

Steve

Last edited by kinetic; 09-02-2009 at 08:25 PM.
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Old 10-02-2009, 09:21 AM
keppar (Graham)
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Thanks all
I'm using primarily a refractor and sometimes a SCT for imaging, mostly DSO's. I want to use my DSLR for some terrestrial photo.s also. As I already own the 40 d (unmodded). I just dont want to waste money on something that won't be an improvment to my images
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Old 10-02-2009, 09:30 AM
keppar (Graham)
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Sorry one more question I currently use a coma corrector on my 40D can this be fitted and used on the DSI ?
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Old 10-02-2009, 11:04 AM
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you likely wont need the coma corrector on the DSI as its chip will not likely extend into the area of the light path that is affected by coma... I know that if I cropped 10% off the left and right sides of images taken with the QHY8 in my refractor, the field appears very flat indeed.. the DSI chip is quite a bit smaller than the QHY8, so you should be fine...

In the SCT you could use an F/3.3 reducer to get a decent field of view, and then you've also got quite a bit of aperture sucking down quite a lot of light... should make for some good photos..

Cheers.
Alex.
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