Need advice on telescope for astrophotography

[cronxeh]

So I am finally getting out in the wilderness on vacation and I thought it would be a great idea to do some astrophotography. I thought of getting a simple enough Nextstar 4SE, but I have a bigger budget and maybe I can get a bigger diameter and aperture. So my question is, which telescope should I get in order to photograph the deep space objects. I might also need a DSLR in addition to the telescope, and I'm not sure if the GPS is built into most of those scopes - so separate module? something I can just hookup via bluetooth or some other ways.

So essentially: high quality optics, at least 6", PC/MAC control, DSLR compatible or proprietary builtin camera, GPS support, Equatorial mount. Budget: $1000-2000 Fine if it is used

Any advice?

 

[Archosaur]

russ_watters is your guy. He's got his own astrophotography site. You can contact him https://www.physicsforums.com/member.php?u=142", if he doesn't find this thread first.

 

[cronxeh]

Hokay well if anyone wants to chip in, I am thinking of

Celestron CG5 Computerized Telescope Mount & Tripod ($595)
Canon 20Da ($385)

Now the question still stands.. which telescope?
I could go with the f/10 Celestron C6 ($380) or f/8.3 Orion Astroview 120mm ($330)

 

[chemisttree]

GPS is not so necessary IMO. If you know where you are, you can enter in your own coordinates if you need to. It is only good for GOTO type mounts. Without the GPS, you can still find DSO's after a fairly trivial alignment procedure. For DSO's you will need a good mount with a smaller diameter scope like 6" since you will be exposing your CCD chip for a longer time period. The CG5 (as a goto that will be the Celestron ASGT) with a 6" is OK but not great for photography. A larger mount is better like the Atlas EQ-G since most DSO's are fairly dim and need many exposures and preferably longer ones. F10 scopes of the SCT type are pretty good when equipped with a .63 or a .5 focal reducer.

I prefer a beefy mount like the Atlas with a short fl refractor but with your budget I would choose http://www.telescope.com/control/telescopes/goto-and-computerized-telescopes/orion-atlas-8-eq-g-computerized-goto-reflector-telescope" The Newtonian gives you the biggest bang for the buck, is fairly portable, comes with a beefy mount with GOTO and allows you to guide for longer exposures. The 2" crayford focuser is suitable for the DSLR. This setup is only $150 more than the mount itself costs.

 

[cronxeh]

How many hours of exposure we talking about here? I take it the CG5 is only OK because of drive errors and would otherwise make the picture blurry on long exposures. Suppose if you take 10 minute exposure shots, and then 'stitch' them together, cropping out the abberations on the sides from drag. How much variance can you expect between different mounts, and can this be compensated by digitally processing the shorter exposed pictures and layering?

 

[chemisttree]

10 minute subs is a pretty long time. The Atlas would be hard pressed to do it without good periodic error correction and it would need to be guided as well. There is a guiding port on the ASGT mount but no PEC. Perhaps you could control the ASGT with your computer and include that bit of functionality (PEC correction) but I still think the Atlas is a superior mount for photographs.

Look online for astrophotography using the ASGT and the Atlas EQ-G. I think the numbers and quality of what you find will tell the story.

You can correct for some of the blurriness due to drive errors by using shorter subs, it's true. It's more better gooder with the Atlas though.

 

[russ_watters]

I'm not the only astrophotographer here, just the one who brags the most...

I agree with most of what has been said here, but in my own words:

Tracking and exposure will be a big problem at that budget because accurate tracking at a reasonably long focal length requires two telescopes and two cameras. Using error compensation on the telescope will probably allow you to do 2 minute subframes and then you can stack them with software.

That Atlas 8 is a great scope and mount (I have a different scope, same mount) and will leave room to grow if you get yourself a guidescope in the future. You'll be throwing away half of your 2 minute subframes though, as that's a pretty long focal length for unguided tracking. With that big of a scope and mount, you will need to consider portability - alltogether, it'll weigh around 130 lb.

That Orion 120mm isn't apochromatic, meaning the colors of objects will separate as they go through the lens. It's a significant problem. If you're going to go with a refractor, you'll want an apo. Also consider that nebulae are BIG! and you don't need much focal length for them. I took the attached pictures with an ED80 and a focal reducer!

I had the Meade equivalent of the Nextar 4 and wouldn't recommend it for astrophotography unless you only want to take pictures of planets. The telescope is slow and the mount is cheap and I'm not even sure the Nextar will do polar tracking (angling the mount toward the north pole).

I'd also consider the C6 S-GT (6" Schmidt-Cas on a CG5 mount) and it's Meade competitor the SN-6 (Schmidt-Newt on an LXD75 for $1000 each or the next couple of sizes up: http://www.telescopes.com/telescope...06+11031&Ns=priceLH&view=36&display=grid_view

Those mounts are roughly equivalent to the Orion Sirius (though the Sirius tends to get better reviews), but not in the same class as the Atlas. So if you can swing the extra $$ for the Atlas, you'll be very happy with ith.

You'll want to keep some money around for accessories, though, so unless $2000 is the telescope-only budget and you have another $1000, I'd try to stay under $1500. If you get an SCT, you'll need a focal reducer. If you get a SN or an APO, you may still want one, but for either, you'll definitely want a Barlow. If you want to use your eyes, a decent 15MM or so eyepiece will be a big help - the ones that come with the scope always have a small pupil and it makes big difference to get even a mediocre replacement. For planetary astrophotography, you'll want a webcam and for deep-sky, a DSLR would be fine.

 

[cronxeh]

Thanks a lot guys, at this point the portability is the real setback. I am going camping and I can't imagine myself carrying an 80+ lbs worth of telescopes. Perhaps I'll have to settle for long exposure DSLR shots, maybe some near infrared stuff and circumpolar star trails for now. Thank you for your input though, this stuff is a lot more involved than I thought at first

 

[Chronos]

An 8" schmidt Newtonian might be worth considering [$1200]. F4 is ideal for astrophotography. A Meade pro II CCD camera with image stacking software, and a good eyepiece, will be under budget [2k]. An 8" f4 OTA has good portability, aperature, and economy.

 

[russ_watters]

"Portability" is a relative thing: you wouldn't want to set it up more than 100 yards from your car - even closer if you need the power for your laptop.