Star trails are my absolute, without a doubt, favorite part of night photography. They look pretty stationary when you stare up at them, but they actually move in a huge swirl across the sky over time. Take a peek:
The guide I have says 2 hours in no moonlight at f5.6, ISO 100.
Here’s my two cents, which you can ignore or not. Stars are constantly moving. It’s not like you’re going to overexpose them, because even within 30 seconds they’re in another part of the sky. Throw your aperture wide open so your star trails are as bright as possible and either A) expose for whatever your foreground subject is or B) Expose all night… or until you get too cold to stand out there.
Here’s why – the longer exposure the more star trails. If you want to have longer star trails, but your foreground is blown out, then you can turn your aperture down. Or your ISO. You’ll have slightly dimmer, longer star trails. But they’ll still be pretty.
Some examples (I want to point out that it was partly cloudy that night, but because the clouds moved quickly, the photo ends up with an interesting haze).
ISO 400, f4, 5 minutes
ISO 200, f4, 10 minutes
The exposures are exactly the same, but the star trails are longer.
ISO 400, f4, 11 minutes. Another hazy sky, which reflects brown instead of blue.
ISO 200, f16, 36 minutes. I do this with Mt. Shasta a lot… sorry.
So, there’s another way to do star trails that I just started using and kind of like. You need a camera with 30 second exposures and continuous shooting mode. You very definitely need a tripod. You also need a free exe file called Star Trails. It’s available for download on the creator’s website.
You take a series of 30 second exposures continuously, using a remote, for as long as you want. Then the program stitches the results together.
The main reason I love this is because you get the same results are a 2 hour exposure, but if you accidentally shoot for 4 hours and your photo is too light, you just take out enough photos until the exposure looks good. It’s stacking each photo as a layer (which would take you 400 hours in photoshop), then giving you the output.
Here’s one I shot the other night of star trails through the trees in our back yard.
I let it go for about 2 hours before my camera battery died. Oops. There’s another tip – fresh batteries and empty memory cards. Especially if you’re doing the star trails program. 30sec exposures for 2 hours equals 240 pictures!
About 3 minutes of letting the program run, and I have this shot. Lovely.
Tomorrow: How to use a flash in your night photography to capture people!