Star-Trails, a beautiful circular spirographic image of the path of the stars around polaris, (North Star) looks eye-catching .
In photography there are few exotic experiments that few people try and very few get it right the very first time. Off-course with advent of mobile phones and myriads of apps that help you in achieving the right results. You can get it right if you follow the guidelines and experiment a bit.
For the uninitiated let me explain few basic astronomical facts. Our mother earth turns on its north-south axis every 24 hours ( roughly) and it also revolves around the sun. Earth completes one revolution around the sun in approx 365 days. earths rotation around its own axis causes day and night. The north pole of our planet points towards a star which we call as pole-star ( in mythology it is called Dhruv ). In fact it is the earth that rotates on its north-south axis but to we people on earth, it looks that it is the stars that rotate around the earth. So if you point your camera at the pole-star and keep its shutter open for sufficiently long time, it creates star trails just like light trails of passing cars we shoot at night.
Nowadays there is a software available that can create beautiful 360 degrees star trails out of the images of star-trail bits you have recorded. It looks beautiful. For capturing this phenomenon you have to follow certain rules. You should have a SLR with wide angle lens.You should have a cable release. You should shoot star-trails preferably on moon-less nights ( Amavasya). use widest aperture, keep the shutter on Bulb mode,Dial the lowest possible ISO, Have a heavy tripod,place it on the sturdiest platform. Figure out pole-star, point your camera at it, focus on infinity. see to it that you have some natural or man-made subjects in the frame, these objects should not hinder your view of the north sky.
After all this preparation, open the shutter and keep it open for say 30 seconds at a time.Allow the camera to cool down a bit as such a long exposure heats-up the sensor. Then again repeat the process…..so on for minimum 100 frames or more
Now download your images to your computer and using the software combine them together to create a magical star-trail photograph.