Circumpolar Trails and Helpful WebPages on Trails

I recently took another photo of star trails from my home in Saida. The result is shown below:

As you may have noticed, the trails make circles around a point near the center. This point is the north celestial pole, and close to it is the bright star Polaris or the North Star. Polaris is not precisely at the north celestial pole, so it too makes a small trail. This is my first picture of such "circumpolar" trails.

I used an ISO of 400, f-ratio of f/7.1, and the minimum 18mm focal length of my zoom lens. There's some light pollution glow in the lower right of the picture, but nothing too glaring. I was able to control the amount of light pollution that showed up in this picture by taking relatively short exposures (30 seconds) consecutively and combining 248 of them. I tried some digital processing on the image, using an unsharp mask in Photoshop along with an "auto colors" adjustment. The resulting image had brighter trails and a more bluish-gray background than the original.

So I hope you like the final result!

I'd also like to share a webpage I came across recently which I think can be helpful in learning how to make a star trails photo. It's written by Steven Christianson, winner of the 2010 Astronomy Photographer of the Year competition, People and Space category.  It's got some good tips especially for figuring out the best f-ratio, ISO and exposure time.

Other helpful pages on star trails include:

http://www.astropix.com/HTML/I_ASTROP/TRIPOD/TRIPOD2.HTM

http://www.rmg.co.uk/visit/exhibitions/astronomy-photographer-of-the-year/how-to-photo-guides/star-trails/ 

Give them a read the next time you plan on trying a star trails photo!

Thanks for reading :)

and clear skies!