Star trails 101

I have been wanting to try to photograph star trails for some time. Ideally pointing the lens at the North Star to get a series of star streaks as the earth rotates.

It’s not as easy as leaving the camera shutter open for a long time. That might have worked with film, but with digital cameras the sensor heats up and adds some ugly colored noise artifacts that mess up the black sky.

The workaround is a technique of taking multiple exposures with a “cool down” interval. Using software the images are stacked together to form a composite shot.

The sky was clear on Saturday and it was the peak of the Orionid Meteor shower. I was HOPING for a shot of star trails intersected by a fireball preferably exploding in the middle of the shot. Alas it was not to be.

Setup was more complicated than I thought. I opened the lens to f2.8 (which was max for this lens), set an exposure length of 60 seconds, manual focus to infinity. I have an interval shutter release (cheap Opteka OP-02) that I set to fire off every 3 minutes.  As you can see in the photo, that was too long, the trails are dotted lines.

My battery drained a lot sooner than I expected. I need to learn how to turn off the review display. I retrieved the camera after only 28 shots (it was getting late) and discovered a nice heavy dew on the lens. It didn’t seem to blur the stars which was nice.

Getting those 28 images merged was more of a challenge than I thought. I have Photoshop CS5 but this is not an easy product to use. I also have access to Google search and that provided the help I needed.

Google pointed me to a Star Circle Academy  blog posting. They provided  a free CS5 action that does all the heavy lifting for multiple image processing, along with instructions on how to use it.

The site has great photography and tons of interesting information.

Keep watching the sky and bring your camera along.


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