Star trails when there is light pollution

[Dave Smith]

Tom (Albireo380) recently posted a very nice image of polar circles. This had to be from a very dark site otherwise light polution can have a drastic effect. The first picture below shows what I obtained with an exposure of about 15 minutes and with the Moon up and to the South.

It is possible to get star trail photos even when there is light pollution by making use of a FREE little program available for download from www.startrails.de

The second image below was obtained using this program. The technique is to set the camera on continuous shooting mode but with (say) a 30s time exposure. The camera will keep on taking 30s exposures with only a tiny gap between them. The program then stacks them together in such a way that the star images come out as the trails but the background sky is no brighter than the brightest single image. It is well worth a try. There is also facility to take darks and have them automatically processed.

The third image is the same as the second with a suitable foreground added. (The foreground image was taken in the daytime but darkened in photoshop)

Dave