Caroline Herschel discovered the open star cluster in 1787 (her husband William included it in his catalog as H VIII.77). It was many years later that the nebula itself was discovered and finally cataloged as NGC 7380.
This image consist of 3h10min Ha, 5h50min OIII and 23h10min SII data. The H694 chip seems to be no too sensitive to SII - with that much exposure time, I expected a much stronger SII signal. I tried boosting it more, but the red quickly overwhelmed the background and stars. This and all the stars made it quite tricky to process this image. After stacking with CCDStack, I did all the processing with Pixinsight:
- Cropping all images
- DBE for all individual images
- TGVDenoise on all individual images
- Another DBE to remove remaining gradients that weren't visible in the monochrome images
- ACDNR for further noise reduction
- Initial Stretch
- I also did a stretch with MaskedStretch which resulted in less star bloat. But the image lost a lot of contrast. I transferred the stars from the MaskedStretch to the other image. I learned about this from one of the many great videos on Harry's Astroshed.
- First to bring out the fainter, outer areas, and then
- (after inverting the mask) to increase the inner layer
It took me many, many attempts to come up with this sequence.