A sky of star trails

On a very rare clear night for me, I have at last a chance to try this in my back garden. Astro photographers will recognise it with ease but for my viewers who are not initiated here is what you are seeing:
This is 83 separate exposures, taken with my 11mm Tokina DX (similar to 16mm on fx or 35mm camera’s), each set at a shutter release time of 40 secs, f4.5 , iso 640, with just a gap of 5 secs between each shot. All the shots were then ‘stacked’ together using a program called StarStax.
I am pointing my lens roughly towards our North star Polaris. Now because of the long exposure and gap between each shot, around 90 minutes had elapsed between the first and last shot. This then showed the movement, not really of the stars but the earth revolving on its polar axis which is lined up with Polaris hence the star here in the centre of the ‘wheel’ is Polaris and all the others have revolved around it some distance. Each white line is a blurred star’s travel over those 90 minutes and 83 exposures. A more complete unbroken series of circles can be obtained with more exposures over a longer time, ideally over three hours and 300 exposures or more. As the wind was gusting, our trees were tossing around and over the 90 minute period a bank of cloud had flown by. Normally my home, being inside the light polluted conurbation of Greater Manchester, is much too bright to capture such things but a new moon (no moon) and a new anti-pollution glass filter has made things better here.

A lot of patience, a sturdy tripod and an electronic camera timer trigger helps here :)

Enjoy full screen on black.

Ps my last attempt at such a thing was in Cyprus just 14 months ago. (PiP)