Astrophotography starter

[RampantAndroid]

Hi all,

I've been tinkering with my D7000 and doing some night shots, but would like to get a little more serious this summer. To that end, I'd love to pick up a telescope and try some better shots of messier objects and going a littler deeper once I've learned a bit.

Now, I gather I want a tracking mount and all that, but I'm confused about how the guide systems work. Some places say to not use an external scope, but a lot of people seem to do it. Stuff like the Celestron CGEM have ports for guiding, but how does that work? Do you NEED to buy an external scope, mount an sensor to it and use software to control the mount? Why can't you get an adapter ring and mount the sensor directly to the telescope forgoing the need for an external scope?

I guess I'm also not totally sure on the best method to start out here. Should I first master doing these shots using a regular lens I already own with a polarie, or should I go all out right now and get a proper telescope and an adapter to mount the D7000 directly to the telescope (prime focus?)

Thanks in advance!

 

[randomrogue]

There's a new astrophotography section at dpreview that would be better but I'll give you a few answers.

1. The extra scope is just a small scope that you use to allign the larger scope to the north pole. It's just not possible with the large scope. You learn where Polaris is and you slightly go off from that. You can buy guide scopes or just use a lazer pointer and do it yourself.

2. I've never used a computer guided mount. Sounds nice but I'm old school and do it manually. Buy/Borrow a book with messier objects and learn some really basic constilations and stars. You then bounce from one object to the next and you learn their relationships. I saw a book once where they had a new object for everyday so that you learned how to build up on a daily basis. I think this is great if you live in an area with not too much cloud cover but Seattle is going to be clouded in. Might be worth checking out though. Also, get the app on your smart phone that shows you the night sky.

3. Personally I think you're getting ahead of yourself. Here's the order you should do this in.

a. Go out, with a tripod, and take pictures of the moon. It's the right time of the month. A remote shutter release is great but you can get by temporarily with the camera timer. Take 5 minutes googling "photography of the moon" for some good starting tips.

b. With a tripod, a remote shutter release, and a fast lens go out and take a picture of a constellation. If you have a f2.8 or faster lens then this is very doable. There's a relationship between the length of an untracked exposure and your focal length. They call it the rule of 600 I think so if you had a 50mm lens you would get a 12 second exposure before star blur. You can clearly see that the wider lens you have the better. Assuming the same f stop. I shoot at 16mm f2.8. You can then start messing with stacking images to get the best possible result. At this stage you'll start understanding how important a dark sky is. Although I can shoot comfortably at ISO6400 or even a stop higher the light pollution where I live is too high so I have to shoot at around ISO1600 which severely limits the photos I get. Preferably you should be running ISO5000, F2.8 or faster, and getting awesome photos after some post processing.

c. Build a barn door tracker. If you have some tools laying around you can build a tracker that's good for about 4 minute exposures and it'll cost you about $150 (don't quote me on that).

d. Buy a tracker. You'll still use your camera and lenses but now it'll track properly and for much longer than 4 minutes.

e. Buy a telescope and an attachment for your camera so that you can take pictures of objects with very long focal lengths.

 

[randomrogue]

Oh and small addition between a. and b.: Do star trails. Fix your camera at a point in the sky and take a long exposure. Generally speaking light pollution is a problem but you could use a remote shutter or a built in intevalometer to take a whole bunch of longer exposures that have star trails and then add them together in post. Preferably take the photo with a foreground subject and get one photo with that foreground subject properly exposed.

 

[Ticky]

Randomrogue speaks truth. If you're feeling ambitious, you could build a telescope instead of buying one. Cheaper, and a fairly achievable project for most people.

Also, you could probably skip the tracker step and go straight to a scope, if you wanted to...