Posted in Moon astrophotography gallery
Someone might point out - how is it possible to create a high resolution mosaic during a lunar eclipse? It normally takes at least several minutes at this kind of focal length, what with the movement of the Earth's shadow across the surface of our satellite?
In order to solve this problem, I had get a little creative. What I did was record the material while moving the mount position vertically (north-south axis) with a speed of 4 arc minutes per second, or 16 times sidereal tracking rate. It took three "swipes" (western, central and eastern part) in order to record the entire lunar disk. The raw video material was then divided into groups of initially stabilized 1936x600 fragments with a 50% area overlap and then stacked/sharpened the usual way. Thanks to the high speed of my camera (over 120 frames per second) each fragment consisted of approximately 200 individual frames, which - coupled with a fair seeing conditions - was enough to bring out a lot of surface details.
The entire acquisition process took only about 50 seconds, during which more than 10 gigabytes of raw material was produced. The Earth's shadow moves at a speed of approximately 1 kilometer per second, so there should have been a displacement of about 50 kilometers between the first and last frame. In practice, Photoshop mosaicing algorithms did a great job of accounting for the minor brightness differences across the disk.
Here's a video illustration of how the source material looked:
- Location: Siemianowice Śląskie, Poland
- Date and time: 2015 September 28, 03:23 CEST
- Camera: ZWO ASI174MM
- Filtering: ZWO G
- Mount: Sky-Watcher HEQ5
- Optics: Celestron C9.25; f = 2350 mm
- Exposure: 3 vertical panes ~1500 frames each, 75% best frames stacked
- Processing: ImageMagick & own scripts (pre-processing, initial alignment) AutoStakkert (alignment, stacking); Astra Image (Lucy-Richardson deconvolution, wavelet transform); Adobe Photoshop (automatic alignment, curve adjustment)
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