Overview
The Earth’s rotation makes the Sun appear to move across the sky during the day, and the same happens to the stars at night. This photo shows the movement of stars around the North Celestial Pole over six hours. The brightest line is Polaris, the North Star.
Background
My original aim for this photo was to track Polaris, but my mount couldn’t quite achieve that angle. So I changed the plan and went for a more conventional startrail image instead.
I told my ASIAIR PRO to target Polaris, and once it got as close as it could, I turned the mount off so that it wouldn’t track. I then took 120-second exposures for six hours, and integrated them in PixInsight. The resulting image isn’t actually that far off the end result.
Most of the editing was done in Lightroom. This was mostly playing about with the contrast and saturation. I needed to clone out some hot pixels too — probably because I messed up a setting with the original PixInsight integration.
Science
It’s a common misconception that Polaris is directly over the North Celestial Pole. Even some astroimagers think this. Polaris is close, but in a telescope view like this you can see that Polaris moves over the course of a night too.
Imaging details
| Date | 21 April 2021 |
| Location | Bristol, UK (Bortle 8) |
| Telescope | Askar FRA400 f/5.6 Quintuplet APO Astrograph |
| Camera | ZWO ASI 2600MC-PRO |
| Mount | Orion Sirius EQ-G |
| Guide | William Optics 32mm; ZWO ASI 120MM Mini |
| Control | ASIAIR PRO |
| Software | PixInsight, Lightroom |
| Filters | No filter: 180 x 120 seconds |
| Total exposure time | 6 hours |
| Image credit | Lee Pullen |
Source data
Seestar S50
Seestar S50 image coming later…
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