Quote:
Originally Posted by cardsharkk04
Looks cool! What was your set up? What does untracked mean? I know nothing about astro photography. Is it hard to keep them from being too noisy?
Hi, thanks for the compliments, although by astrophotography standards this photo would be considered a piece of ****.
Anyway, I am just starting out, so whenever I can capture something that I cannot see with my naked eye, I am happy.
The phrase untracked means that I did not use a mount to follow the sky. So basically I just used a cheap tripod, and my exposure time was limited.
You can have three types of mounts: fixed, alt-az, GEM.
Fixed: this is what photographers use as a standard tripod. This is what I use. So I am limited to short exposures b/c I do not have capabilities of following the sky.
Alt-Az: this is a common mount for telescopes. It has the capability of moving left and right, and thus is able to stay centered on stars. With this type of mount, you would be able to take longer exposures than you would with a fixed mount, but the image would eventually suffer from field rotation.
Unfortunately, the night sky not only movies from east to west, but it also rotates (around polaris, the north star). The Alt-Az mount is unable to account for field rotation, which means that while this mount will track the object, it will not rotate in accordance with the object.
Equatorial Mount (GEM):
This is why all professionals use equatorial mounts. These mounts are designed to not only track an object, but also to rotate so that extremely long exposures are able to be taken.
On my tripod, @ 50mm (1.6 crop sensor) I am limited to about 8 second exposures. When I really wanna be greedy, I push it to 12 seconds. Longer than 8 seconds and you can see star trails. Noise isn't a big issue and even at ISO 2000 (which is what I shot that image at) it can be edited out fairly easy. But keep in mind: if you have a lot of light pollution the image will get blown out.
With an Alt Az, I would probably be able to go about 30-50 seconds.
With an Equatorial Mount: in theory, my exposures could go on forever.
Most people say that if you wanna shoot astro, the most important thing is a good mount. Many people buy a GEM for under 1k, only to find out that it does not track they sky very well (thus limiting your exposure times). A popular beginners mount is the Orion Atlas EQ-G mount. This sucker costs about 1.4k, but it will allow you to take 5 minute exposures and it will handle a fair amount of weight.
If you are shooting wide like I am (50mm croppped @ 1.6x), you don't need totally precise tracking, b/c you are so zoomed out that you will not notice the subtle errors). So, I could prolly get by with a cheap $300 GEM. But if you strap on a 400mm lens, or use a telescope for astrophotography, you will need the precision.
In that picture of Orion, I used a 60D, and I stacked several exposures. What this means is, I fired off about 12 pictures, and then combined them all into one master image using a free software called deepskystacker. I shot RAW, which is an absolute must. What stacking does is increase the signal to noise ratio. So in theory it should give me a more clear picture (but it will not show me the sky deeper, only increased exposure would do that).
Now... editing astrophotography images. Well... this is very hard. To get good images you must take dark frames, bias frames, and flat frames. These are images that are added to software so that the software can calculate the noise and lens field curvature, to enhance an image. After you edit and stack it all in RAW, you export it and tinker with it even more in photoshop. It really is a long process. My suggestion would be to read:
http://www.astrophotography-tonight....phy-on-budget/
http://www.astropix.com/HTML/I_ASTROP/TOC_AP.HTM
So basically if you have DSLR and a tripod you are good to go. Download a free program called Stellarium, find a portion of the sky that might have a bright nebula (m42 orion) or galaxy (m31 andromeda) and see if you can capture it.