Shutter speed for Earth rotation??

Ambrola

Can someone tell me what settings to use to get the stars in rotation. I think I have to use high ISO and shutter speed of about 30 seconds?? Any help appreciated. Nikon d-80, should I use a 70-300mm or a 18-135mm??

chuckinsocal

I've read here on dgrin that it's at about 30 seconds when you start to see star teails. So maybe 60, 90, 120, or more depending on how long you want the star trails. As for the lens, I guess it depends on how wide or narrow a field you want. High ISO makes sense to me but I can't tell you how high.

I think it's gonna boil down to experimenting until you get the effect you want.

hgernhardtjr

A lot longer than that, I'm afraid. In film days I did exposures of over an hour. Also used a "cold camera" and "hypered" film a few times.

But battery life can be a problem with dSLRs. "Bulb" was my friend on film cameras.

You can also try taking numerous shorter exposures (say 30 seconds each) with your dSLR on a solidly fixed and non-moving tripod every minute or two over several hours, though, and "stack" them in PhotoShop or similar programs, too. Read some good information here: http://www.danheller.com/star-trails.html and here http://www.astropix.com/HTML/I_ASTROP/TRIPOD/TRIPOD2.HTM. Just search on "star trails" to find many more helpful sites.

ziggy53

Photographing star trails normally ranges from several minutes to several hours. The field of view (FOV) makes a difference as a long focal length will show more motion in the field than a short focal length shows. Where you point the camera also makes a difference as those parts of the sky close to the polar north show less motion than those in the opposite side of the sky.

A higher ISO will reveal more stars, as will a larger aperture. You will want to find a good compromise between exposure duration, aperture and ISO, to go along with the particular FOV.

With a long exposure comes more random sensor noise as well as sensor, so you may also want to consider high-ISO noise reduction to help control the sensor noise. This does double the exposure time so you might also consider taking a single dark frame to use for manual noise removal.

Like "chuckinsocal" already mentioned, some experimentation will show what's required for the particular visual effect you desire.

Do make sure to have several fully charged batteries before you begin. Battery consumption gets to be a factor with long exposures, and some cameras may even be damaged if the power fails completely during long exposures.