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Help please! 8" Newtonian Astrograph (Orion) v *" SCT (Celestron Orange tube)


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Hi!

I am considering the above two telescopes for astro imaging. I was wondering if you have any thoughts on which would be a better choice for imaging smaller DSO's (galaxies especially). I was wondering if vibrations would hinder the images taken through the f/3.9 Newtonian because of its higher moment than the Celestron C8 orange tube. I do not live in a very windy area at all, so I am thinking this may not be a problem, since I have an infrared remote control for my camera. And all in all, whose optics do you think would be superior, the Celestron C8 Orange Tube, or the Orion newtonian Astrograph? For smaller fields of view, I'd be using a barlow on the Newt, and a coma corrector when necessary. If using the Celestron orange tube C8 SCT, I would use a reducer. Whichever I get, it's going on an Orion Atlas mount.

Thanks!

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For smaller galaxies, you want a bit of focal length, but at the same time, you want to make it as easy as possible for yourself. An SCT has huge focal length and a quick search will throw up lots of advice against such a choice. I am not going to disagree. The Newt is a better choice, but as a starting setup it means you have to get an awful lot right before anything good will come from your efforts. As mentioned above a refractor is as clean as it gets for beginning, but seeing as you are after the titchy stuff, you could up the focal length somewhat and still retain the ease and also the pixel scale required with a DSLR, which is what I am assuming you are going to use. A refractor of around 100mm aperture and 700-900 focal length might be good for you. Don't worry too much about the F ratio when you are after the small things, as they will fit on your chip whether you use a reducer or not.

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Presumably if you've got an IR remote you're using a DSLR not the best thing for a Newt as you can have trouble focusing or an SCT  due to resolution although I have taken images with DSLR on my SCT @ f/1O

As said if just starting out a small refractor is best.

Dave

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You need to do some calculations. Look up the angular size of the galaxies you want to image and then see what focal length you need to give a reasonable size image given your pixel size and the resolution of the intended scope.

Once you have some data you will be better placed to make a decision. 

While a small refractor may be a good place to start imaging I suspect the image scale will be too small, but a calculation will confirm one way or the other.

 

Regards Andrew

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  • 2 weeks later...

I would stop where you are and do a good bit more reading on what will work. A DSLR in a slow scope at long focal length is not the place to be aiming for. If I were you I'd consider an F5 Newtonian, not a fiddly F4. Fast enough, more tolerant on all counts and a bit more focal length.

Olly

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