Star Trails

[phobos27]

Hi, I am looking at doing some star trails this evening and I was wondering what the minimum time the exposure would have to be to start to get a nice trail going. I am going to do a series of 30 second exposures and put them into star-Stax. I have done this 4 times before but I'm looking for the quickest possible time. Would 1 hour be good enough?

Regards Nick

[killswitch]

If you have done it before, just throw an hours worth of images in starstax and see for yourself.
This one was only 30 mins:
http://www.iceinspace.com.au/forum/showthread.php?t=115858
(http://www.iceinspace.com.au/forum/showthread.php?t=115858)
Also the longer the focal length the faster it will streak

[phobos27]

That was a great image. 30 minutes should be plenty because i am using an 18mm lens. Thanks for the advice!