Overview
The Cave Nebula (Sh2-155) lies 2400 light-years from Earth. Radiation from hot stars is compressing the gas, triggering waves of star formation.
Background
This was the most difficult image for me so far. I worked at the editing all day before I finally had something I was happy with — the 7th version! Part of the reason it was so tough is because of the high noise levels. I cut this project short at 18 hours because brighter winter targets are getting high in the sky, and I want to move onto them. Also, the integrated shot had banding issues, which I’ve never had before. I had a tricky time removing them until I discovered that PixInsight has a utility called CanonBandingReduction that fixed it in literally three seconds!
I normally crop my images in at least a little, but during editing it was obvious I’d captured a fair amount of surrounding nebulosity not often seen in images of the Cave Nebula. So, I kept it wide.
Check out this comparison between a single sub and the final edited image to see just how much is gained by integrating and processing:
Imaging details
| Date | Nov – Dec 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 Plus |
| Software | PixInsight, Lightroom |
| Filters | Optolong L-eXtreme (Ha/OIII): 540 x 120 seconds |
| Total exposure time | 18 hours |
| Image credit | Lee Pullen |
Source data
Seestar S50
Seestar S50 image coming later…
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Astounding! Your “slider” comparison makes it look like magic. With 120 second subs and fast f/5.6 you probably use no gain on the camera for benefit of maximum dynamic range?
Thanks! I always use Gain 100 (set via the ASIAIR Plus).