When we contemplate the sky for a few hours, we notice that the sky seems to turn from East to West, dragging with it the Moon, planets, stars, etc. In fact it is the Earth which turns while the distant stars are more or less fixed. By leaving the camera shutter open for a long time (1 hour in this photo), we get a “star trail” which shows us the rotation of the Earth around the celestial pole.
The pole star (Polaris) shows us the general direction of this celestial pole but is not there exactly, as this photo shows when we see Polaris just a little below and to the right of the celestial pole. The circles should normally be perfectly circular, but the short focal length of the “fisheye” lens distorts the perspective a bit.
Camera: Nikon D90 and Nikkor 10.5mm lens
Exposure: 29 x 60 seconds at f/2.8 and ISO 1600
Assembled with the software program Startrails
Place: Notre-Dame-des-Bois, Qc
Date: April 9, 2021