Pinwheel Galaxy (M101) 4-27-25
Messier 101, called the Pinwheel Galaxy, is a spiral galaxy 21 million lightyears away and is nearly 3 times larger in diameter than the Milky Way. In this image, peculiar galaxy NGC5474 is visible near the lower-right corner, and lenticular galaxy NGC5422 is visible near the upper-left. A number of other small galaxies are visible in the central region of the image, including NGC5473, NGC5477, and PGC49919.
I shot this image in the spring, but had trouble processing the data on account of my ongoing issues with overexposed stars. I first tried my usual stacking process with DSS but did not like the result, so I gave Siril a try. I found that Siril, while more complicated to use, has some helpful tools for star reduction and its interface for histogram stretching is more detailed. I have not yet made full use of Siril’s star reduction tools (in particular, removal/recomposition and synthetic star repair), but I will likely reprocess with one or both of these in the future.
I also made an effort to get away from Adobe software for this photo. While editing my last several astrophotos, I found Lightroom helpful for post-processing, but I had some concerns about getting trapped in the Adobe ecosystem. I am still settling on a replacement process - PhotoScape X has a limited set of capabilities, and GIMP works well with the exception of noise reduction. For this photo I used GIMP, but I may utilize other programs during reprocessing.
This was one of my first projects using the Explore Scientific 2” Field Flattener for f/5-7 telescopes. I was very happy to capture an image with decent edge data, as unfocused edges were a big problem during previous imaging sessions.
Overall, I am happy with my progress so far. Compared with my image of the Triangulum Galaxy, I was able to show more contrast and depth, and while I am still refining my data processing methods, the results are steadily improving.
Technical details:
- Lens: SkyWatcher 120
- Camera: Nikon D3200
- Mount: SkyAdventurer 2i
- Optics: Explore Scientific Field Flattener
- Filters: N/A
- Exposure: 208x45s at ISO800
- Corrections: 77 darks, 78 flats, 78 dark flats
- Stacking: Siril
- Post-processing: GIMP
- Bortle: 4
Notes for improvement:
- Some of the brightest stars are still overexposed. As noted above, I hope to improve this using Siril’s star removal and recomposition tools and/or its synthetic star repair tool.
- GIMP’s denoise features were not as useful as those in other programs, and I was unable to open the GIMP output in PhotoScape X because of issues with either color depth or metadata. If I can resolve that issue, I will update the image with improved noise reduction.