First Telescope, need advice (Celestron G8-N?)
Posted 09 May 2021 - 12:33 PM
Recently, I’ve found a used Celestron G8-N with a CG-5 goto mount for a reasonable price (600 Canadian). It also comes with a 26 mm plossl eyepiece, which from what I can tell, is pretty decent.
I can’t find too much about this telescope, and from what I’ve found, it’s an older version of the C8, but a Newtonian instead of an SCT. It has a focal length of 1000 mm and a focal ratio of f/5.
I know that SCTs are hard to deal with when starting out, but what about this Newtonian?
I currently don’t have anything other than my camera and a tripod for that, so I would need a telescope and motorized mount. My tripod is way too light to use for anything other than my camera.
If this is not a great telescope for me to photograph smallish DSOs, what would you suggest? I would really like it to be under 700 Canadian (ideally around 600) with everything I would need. I know it’s not much in the grand scheme of things, but I’m in university, so I can’t afford to spend a ton.
Posted 09 May 2021 - 12:52 PM
I believe you should stay with your lenses (300mm is a decent focal length) and advance to tracked astrophotography. I cannot vouch for the CG-5 since I haven't use one myself, but from the things I've read around it can be a hit or miss. You might need to tear it down and tune it in order to get the most out of it.
Regarding the newtonian, I'd pass. There are so many things to learn once you start tracked astrophotography (polar alignment, balancing, cabling, guiding, dithering, meridian flip etc.). Keep it simple, stay with your lenses....for now
If you are ready to start with tracked astrophotography I'd invest all my budget in the best mount I can get.
Edited by nyx, 09 May 2021 - 12:54 PM.
Posted 09 May 2021 - 01:04 PM
The classic advice is to start with a small, lightweight, wide-field refractor, because learning astrophotography is much easier when you minimize equipment challenges. But your budget is a severe constraint. Not gonna lie, 1000mm unguided is likely to be quite the project.
The problem with SCTs for beginners is not the optical formula, but simply the size and focal length. 1000mm is a lot, and a Newtonian is longer than an SCT, so the mount's fighting more moment arm. You'll also likely have collimation issues to deal with.
The other bit of classic advice is to spend everything, if need be, on as good a mount as you can possibly afford, and put off optics for later. So you could scour the classifieds for a better mount, and put your camera and lens on that.
If you simply must have a longer focal length, then I doubt you'll do a lot better than this for your budget. I have no idea if the G8-N is any good for photography, but people have done work with the CG-5. If the Newt doesn't work out, the CG-5 will probably give you better images with your 300 than you can get now, at least. And you could add guiding to it later for not a ton of money -- you can get a perfectly cromulent guidescope for $50 brand new, and scour the classifieds for a guide camera (it doesn't take much), and run it with a $35 Raspberry Pi.
Posted 09 May 2021 - 01:11 PM
The CG-5 mount *does* offer tracking, and is not a bad mount at all, but the G8-N is too heavy a load on it for astrophography (non-frustrating astrophotography, anyway) and too long a focal length.
It might be OK to buy it for *visual* use, but for astrophotography... really, don't even try it. I would just get a DSLR camera mount like this. You may be able to find something cheaper, I would ask in Equipment (however, ADM stuff is high quality).
The price is not that great a deal, BTW. The CG-5 (make sure it has the *steel*, not aluminum legs!!!) is a pretty old mount. C8N's are cheap scopes. I would think closer to $350-$400 (USD) for the combo would be fair. Try to get him to come down in price if you decide to go with it.
An alternative *new* mount that fits your budget is the iExos-100 PMC-8. You can't really get a mount *and* scope for your budget, so waiting is the best option.
Posted 09 May 2021 - 08:43 PM
Could I take a 30-60 second exposure without running into star trailing, or am I gonna die just trying to get 15 seconds without a guide camera?
Posted 09 May 2021 - 08:59 PM
From what Stelios has said, I'm guessing here that even guided, that scope on that mount is going to be really difficult. Unguided...yeesh.
Posted 09 May 2021 - 10:16 PM
The G8 N had a built in coma corrector that didn’t do a very good job and most user accounts weren’t favorable for astrophotography.
i agree that 1000mm at F5 would be difficult without guiding.
I currently use a Celestron C5 with a reducer to 780mm and it gets excellent images unguided on a lightweight EQ mount. The scope is only 6lbs and all in at 7.2 with my DSLR. The native focal length of the C5 is 1250mm so with a scope like that, you have the option when you’re ready.
Posted 10 May 2021 - 04:51 AM
One simple option is to go with something like the iOptron SkyGuider Pro mount. You can put your DSLR on it, it handles basic rotation, and can get 2-3 minute exposures with a 300mm lens with no star trails with good PA.
I got one of these recently and really like it. It’s easy to use and the PA can be dead on. A ball head accessory will be useful for basic DSLR imaging. You can also use the counter weight setup as it, which also works well.
There are some simple iPhone apps that can assist in doing PA with this setup.
Posted 12 May 2021 - 05:39 PM
Weird coincidence, I just came across this post today. Are you located in Ontario? If you are I think I beat you to it, I just picked up a used G8-N and CG-5 this morning.
I'm also just getting started in astronomy and astrophotography, so I'm not an expert on anything. I was interested in the ad because of CG-5 only (for visual astronomy purposes). Apparently the G8-N is iffy at best from what info I can find (it has a corrector lens in between the secondary and primary), but I figure at worst I can play around with it for a couple of nights, at best I have bonus so-so 8" telescope. For astrophotography I don't think this would make a good setup at all, there's no guarantee the focuser even moves inward enough for a camera to reach focus. Even if it did the focal length is long and the OTA is heavy, I don't think the CG-5 could cut it in terms of tracking accuracy for astrophotography.
There's a lot you can try with just a camera, tripod, and image stacking software. Some people are able to get pretty incredible shots, even with a kit lens, it just takes a little patience. I'm nowhere close to taking pictures of any DSOs or planets but I tried taking a picture of the Lyra constellation early this morning with my D5100, an old 85mm lens, and DeepSkyTracker (it's free) and despite the super-lame target I was pleasantly surprised.
There's a YouTube channel called Nebula Photos that explains how to do everything really well, and without having to buy a bunch of new stuff. You could also check out Forrest Tanaka's videos. If you want to see someone constantly flexing all the shiny new tech then there's AstroBackyard.
Edited by MSH, 12 May 2021 - 05:40 PM.
Posted 12 May 2021 - 06:20 PM
I (evidently) need to do more research about telescopes for imaging, but I might try and snag a refractor and mount at some point.
Don’t worry about the target or if the photo isn’t perfect. You’ll get there and honestly, just looking at the sky is awesome!
Good luck and I hope the skies stay clear!
Edited by TomSawyer10, 12 May 2021 - 06:22 PM.
Posted 12 May 2021 - 07:52 PM