STAR TRAILS
🔭
Askar FRA400
📷
ZWO 2600MC Pro
🌃
Bortle 8
⏱️
6 hours
🗓️
April 2021
Overview
The Earth’s rotation causes the Sun to appear to move across the sky during the day, and the same motion applies to the stars at night. In a long exposure, this apparent movement is revealed as star trails rather than fixed points of light. This image shows stars circling the North Celestial Pole over a six hour period, tracing smooth arcs across the sky. The brightest trail belongs to 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 2-minute 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.
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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.
Kit list
This is the equipment I used to capture the image.
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Telescope: Askar FRA400
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Camera: ZWO ASI 2600MC Pro
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Guidescope: William Optics 32mm Slide-Base Uniguide
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Guidecam: ZWO ASI 120MM Mini
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Control: ASIAIR Plus
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Example source data
Here’s an example single subframe and freshly integrated stack, just with simple stretches applied.
Seestar S50 image
Seestar S50 telescope coming later…
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