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Old 07-02-2012, 12:35 PM   #1 (permalink)
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anyone do astrophotography?

I have a friend who has some telescopes so I bought an adapter to use on my camera. I have yet to get good pictures. I have no idea what settings to use. for now I have only been taking pictures of the moon. Every picture is out of focus, and redish. I have no idea what ISO to use. My camera is also heavy (Sony A77) so the focus knobs are not strong enough to hold focus but they should be better than what I am getting.

Any hints or storys would be great.
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Old 07-02-2012, 01:18 PM   #2 (permalink)
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I haven't done any myself but apparently you can get good result

"The total exposure is 60 minutes (12 frames, each exposed for 5 minutes and stacked). ISO was set to 800. 530 mm focal length at f:5."

Sorry, folks! No A77 ghosting (60 minutes Pleiades)!: Sony SLR Talk Forum: Digital Photography Review

Don't know how much help this will be tho, it might be your camera to telescope mount or something to do with your telescope.
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Old 07-02-2012, 02:34 PM   #3 (permalink)
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found these settings on POTN.

Canon 40D
300MM
ISO200
1/800
F8
Tripod
Mirror Lockup
Remote
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Old 07-02-2012, 02:37 PM   #4 (permalink)
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this might help too:

Astro Technique How-To's - Canon Digital Photography Forums
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Old 07-06-2012, 08:14 PM   #5 (permalink)
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Astrophotography is all about gathering light, not merely sampling from a scene abundant in light as you do in normal photography. That is, you want an aperture that is as big as practical for your hardware. (Decent fast primes wide open or barely stopped down, depending on lens.)

ISO depends on the camera/film you are using, but you want something as low as possible for the time frame you are using. 800 or 1600 might sound good if you're thinking like a photographer shooting in a dim room, but both those are going to introduce more noise and grain than 400 or 200. You want to maintain as good of a signal to noise ratio as you can, so push your ISO down.

Time becomes the tricky part. Why? Because you're not taking a photo of a mountain lit by a bright sun where your exposure is over and done with in a fraction of a second. You're trying to gather as much light as possible from billions of miles away. And your target is moving.

With a 'wide' angle lens (for astrophotography at least) of 50mm, you might be lucky to get a 5 second exposure without your stars beginning to deform due to their movement. This time goes down as you use a longer focal length.

To push your exposures longer, you're going to need more gear, specifically an equatoral aligned mount with a tracking motor. Cheap setups will let you push your exposures with long focal lengths up into a minute or two. Google Barn Door Astrophotograhy for DIY options. Double hinge works well. Higher end ones can let you push your exposures up even longer, which means you can drop your ISO even more for a cleaner result.

Alt-Azimuth mounts, even computer guided tracking mounts, aren't really suitable for photography due to their movements and vibrations. To track, then basically end up zig-zagging across the sky to 'stay on target'. The end results are far inferior to a polar aligned mount.


For strapping your camera onto a scope so you're using it as a lens, things can get tricky with a lot of them. The problem is often your focus system on the scope, as most commercial ones do not offer enough back travel. Look at your eye, and where that sits in relation to your eye piece. Now look at your typical dSLR camera. You'll notice that the sensor is buried back inside the body, while your eye is positioned so that you can bring it closer to the scope. What happens is that your focus then happens somewhere between your eyepiece tube and the sensor of your camera. You can get around this one of three ways: 1. But a different camera designed to mount more like a standard eye piece. 2. Change/modify your focus equipment on the scope. 3. Buy a different scope.


And like I said before, astrophotography is about gathering light, so often you will want to take lots of photos, and then use software to 'stack' them. This allows a computer to analyse the data, including extra data like "dark frames" or "Flat frames", which are photos taken with the same settings as your normal photos of the sky, except darks allow zero light hitting the sensor, and flats receive an even coating of white light. Collect a suitable amount of these, and it lets the computer work out what part of the data is the actual light coming from the stars, and what is just junk caused by flaws in your sensor.
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Old 07-06-2012, 11:47 PM   #6 (permalink)
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That is alot of good information. as of right now I am trying to capture the moon as clear and big as possible. I will try running a few differnt ideas. I will try playing around with the mount setup as I am using a telescope for the lens.
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Old 07-07-2012, 10:39 AM   #7 (permalink)
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The moon is actually more like traditional photography than astrophotograhy. It is 'close' to us, and usually bathed in massive amounts of sun light. You're really shooting a nice sunny day when you're taking a photo of a full moon. My last decent photo of the moon that I was happy with, was actually a hand held shot from my 200mm f/4, 1/1000th of a second, and ISO 200. Hand held shot of the moon.

I strongly suggest finding a good astronomy forum to hang out in. They will likely be able to offer more information on getting your gear setup.

A lot of telescopes are fairly slow, f/6 to f/10 or worse, which is very bad for trying to get the stars, but can work well for planets. The moon is actually a great target for very slow scopes, as your focal length of the lens, how long it is, is what give your your magnification/narrow field of view. And because it is insanely bright, stopping your aperture down doesn't hurt as much as when you're trying to get faint stars.

Good luck.
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