
M8 and M20
Hello everyone. I wanted some help and constructive criticism with my recent M8 and M20 project. Both in my processing/post-processing workflow and on ways to improve the final image.
Equipment:
- Canon Lens 100-400mm F4.5-5.6L, using 250mm and F5.
- Canon 7D Mk2 stock
- Orion Atlas EQG
- Svbony Mini 30mm Guide Scope
- ZWO ASI120MC-S
Acquisition:
- 461 x 60s with ISO 1600 - Total 7h41min integration
- 60 darks
- 50 flats
- 50 dark flats
- No bias
- Captured with NINA
- Guiding with PHD2 - Guiding for the most part was OK. RMS around 1.1 to 1.3" (image resolution is 3.37"/pixel)
Processing:
- Stacked in DSS, with drizzle x2.
- Processed in Pixinsight:
Pre-stretch:
1. Dynamic crop to cut the edges.
2. Automatic background extraction with Function Degree set to 1. I used ABE instead of DBE because DBE was giving me some weird background patterns. ABE was more consistent with the perceived gradient.
3. Background neutralization
4. Photometric color calibration
5. Multiscale linear transform for noide reduction > made a mask using luminance extraction and some histogram transformation to protect the brighter parts of the image. Used very mild parameters (layer 1: Threshold 1.000, amount 0.5, iterations 2; layer 2: Threshold 1.000, amount 0.5, iterations 1; layer 3: Threshold 0.500, amount 0.5, iterations 1; layer 4: Threshold 0.500, amount 0.5, iterations 1).
Stretch and post-stretch:
1. Stretchet using histogram, in a step by step basis. Also, increased a little bit the midtones of the red channel (which was lagging way behind). I tried to use Arcsinh Stretch, but it would make the stars extremely ugly, probably because it exacerbated the chromatic aberration from my lens.
2. Used Starnet to generate a star mask and a starless image.
3. With the starless image, I ran several instances of noise generator and convolution, topped with a slight decrease in saturation, to make the voids created by starnet more similar to the background noise of the image (starnet produces a starless image with lots of artifacts in place where the stars were).
4. With the star mask, I produced a Halos mask following the steps by Adam Block.
5. Ran one instance of substitution using pixel math and the starless image, following Adam Block's Star de-emphasis article. Next, I ran two instances of MorpTransf (erosion) using a similar halos mask. I thought that combining both procedures worked best, since my starless image contained too much artifacts to use it again and again.
6. Using a proper mask (range mask - star mask to exclude stars), I used Multiscale linear transform to mildly increase detail in the nebulas (Used bias +0.050 in layers 2 and 3).
7. Ran a scrit of Dark Structure Enhance at 0.2 intensity (standard is 0.4).
8. Using a range mask, I desaturated the background a little bit.
9. Using Curves, I slightly increased the contrast using an S-curve
10. Again with curves, I finished increasing the saturation.
Thank you for your help!