Creating star trails with a DSLR

[mjs1973]

I have created some digital star trail images in the past by combining multiple exposures in Photoshop. A very long, single exposure with a digital camera is going to produce way too much noise, so stacking multiple shorter exposures helps to eliminate that problem. In the past, I have combined up to 10-15 images with exposures up to 10minutes long. These 10 minute exposures produce a lot of noise as well, so I wanted to try to combine a lot more shorter exposures.

Moose Peterson had a recent blog post where he detailed the method he uses to create star trails out of several hundreds of short exposures. Here is a link to that post. Be sure to click on the link to the PDF that he has. This will take you to a great article that walks you step by step through the process.

Last night, the stars were out and there wasn't a cloud in the sky, so I headed out to capture some star trails. I set my camera up, and set my remote/timer to take 30second exposures. I set my aperture to f/5 and ISO to 200. Once everything was set up and taking photos, I went back to my truck and fell asleep. About 2 hours later I woke up and noticed that there were no more stars! Sometime during my nap, the clouds had moved in. So I went back to the camera to check it out. I put the lens cap on, and took a dark frame shot, then grabbed my spotlight and did a few frames where I painted in the FG.

Looking at the images this morning, I found that I had about 93 exposures before the clouds rolled in. This gives me the equivalent of about a 46 minute exposure.

I used the free Startrails program that Moose mentions in his PDF to combine all of the star images and the dark frame image together. Here is the link to the program. It works great! I did use Photoshop to blend my FG images together and to add them to the image that I created using the Startrails software to get my final result. The Startrails software is incredibly easy to use, and it's FREE! This will be the method I use in the future when I want to create star trails.

[GB1]

This is really neat Mike - so, the individual shots are taken immediately after each other? I wonder if batter life issues come into play. In this shot you can tell it wasn't left open for a very long combined time as the arcs aren't very long. Looks like about 2 hrs. But it works.

I need to DL that app and try it. Post some more

G

[mjs1973]

Hey GB. Yes, the photos are taken right after each other. One second is the shortest amount of time I can set my remote trigger for to fire each consecutive shot. (I hope that makes sense.) I set my timer to take a series of 30 second exposures, one second apart. Battery life is an issue. I have a battery grip on my 40D so I had 2 fully charged batteries. My goal was to just let it go until the batteries were dead. I shut it down a little after 2 hours because the clouds came in. My batteries were just about dead. It was also below freezing so I'm sure that had an effect on my battery life as well. If you read the PDF file that Moose has on his blog, he mentions an external battery that you can get to increase your exposure times. The shot I posted above is about 45 minutes worth of exposure.