What speed do I use to shoot the night sky? I tried last night, first tried with 30", then 10", then even 6", but all the times there were movement from the stars themselves, like this:
And that was with 4 seconds speed! How do I shoot then? With speeds like 1 second, there is not enough light, and I have to use really high ISO, which adds lots of noise...
The rule of thumb is to shoot at 600/f to avoid star trails, where f is the "focal length" (35 mm equivalent).
For example with a 200mm, 600/200=3s. The minimum shutter speed is 3 seconds.
Anyway, the best approach is to try and eventually change your settings.
Have a look at What times and settings should I use for taking pictures of stars at night and falling stars? and What is the "Rule of 600" in astrophotography? (thanks to mattdm for this one)
Use internal image noise reduction and image stabilization to get a photo of a bright astronomical object, such as the moon. By accident, I found that image stabilization kept the moon's image fixed, even though background stars left trails, during a long exposure.
If you have access to an astronomical telescope with a clock drive or manual slow motion controls, mount the camera on the 'scope and use the telescope drive to track a star.
Take a number of short exposures and use software to reduce noise (or create star trails) such as the free StarStaX. See Noise Reduction by Image Averaging for details.
The issue with all these techniques is that you'll need to compose scenes including terrestrial objects as well as the sky in layers, because the images move relative to each other.
First things first, you need a tripod. You want to pick a night with as little air traffic and as few clouds as possible. It should also help if there is little air pollution.
Next, pick your spot and angle. You may want a foreground context to make your photo more interesting. Take a few practice shots using flash to have a rough idea of what your background will look like.
If you want to shoot the Milky Way look for a long cloud stretching across the Milky Way. It will be almost foggy but not blocking stars.
So once you have your shot aligned, open your aperture as wide as it goes. Set your shutter speed to 600 divided by focal length (Anything longer will create star trails.)
Optimal ISO range is about 2000 but once you have taken a few shots you can adjust accordingly. Sometimes I go lower sometimes I go higher.
Try to time your shot when there are no planes in the sky. Also take a bunch of photos. Change it up and try different things.
