The Rules of Astrophotography #1

"Smokey, this is not 'Nam, this is bowling. There are rules." - The Big Lebowski

One quick tip about shooting astrophotography images like the one above is to use the rule of 500, which I will explain. Shooting wide angle astronomical images is exciting and fun and there are a multitude of ways to create an image with the Milky Way and stars, but one of the very first steps is learning what settings will work.

First off, the earth is rotating pretty darn fast. As you know, if you try to use a long shutter for something that is moving across the field of view, it will streak. The earth is moving but from our perspective, we see the sky move across our field of view. Well, how do we keep the stars from looking like streaks and more like pin points of light? You need keep your shutter open long enough to let light in to your sensor, but short enough that this movement is minimized. This is the rule of 500: 500/your lens in mm. For a crop sensor camera, this will be 500/(mm *crop factor). This will give you the length of time your shutter can be open without noticeable star trails or movement in your sky. This number should always be rounded conservatively as well. An example would be 500/24mm = 20.83 seconds which would be rounded conservatively to 20 seconds. Another example for a crop sensor camera would be 500/ (14mm * 1.6 crop factor) = 22.32 which would be rounded conservatively to 22 seconds.

This rule is just an easy way to make sure that you get the max benefits of using a longer shutter speed and getting sharp star points at the same time. There is always another thought process or way of doing things and I personally use the rule of 500 (and not the rule of 600) because I print my images and prefer them to be large pieces of art work. If you are looking for more light and don't think you will print ever then the rule of 600 may work for you. Rule of 600 is same as 500 in the arithmetic.

Next week I will be going through my checklist of what I look for before I head out to shoot the Milky Way. If you have a question, please add a comment and I'll try to answer it. Also, sign up for the newsletter to stay up to date on my posts and tours! I give tips every week on astrophotography, lighting, posing, education, and why traveling is the best thing you can do for your photography ( and for yourself ).