star photography

[nemesis256]

This past weekend, I finally got the chance to photograph stars. While I was able to have some stars show up in my picture, it was far from amazing. I was shooting with a 35mm prime at 1.8. I tried many exposures, and found that at around 45 seconds, the stars start to trail. And the shorter the exposure, the least amount of stars appear. Also, many of the stars appear blue or orange/red. what causes this effect? How does one take a photograph where you can see thousands of stars, and possibly even the Milky Way?

[sk66]

Basically, you take a bunch of "underexposed" images and stack them (in a mode such as overlay), or you take a bunch of properly exposed images and average them....PITA to match them up though...Otherwise you need some type of "tracking" setup to prevent the trails.
What causes the stars to change colors, not sure...color wavelength frequency maybe, or near sensor interpolation maybe.

[Eastree]

You have some options, depending on exactly what you want.

For crisp stars, you'll need a tracking mount so you can (a) or (b) while keeping the camera pointed at the same place among the stars as the earth rotates.

For star trails, you can ....


a) use a lower ISO (as necessary for the sake of your exposure) and a very long exposure, risking sensor noise from such a long exposure

or

b) use some stacking software which basically layers shorter exposures on top of each other, eventually resolving the better exposed (black field with bright stars) night sky.