20210922-23-24 - Sh2-173 CAS The Phantom of the Opera Nebula - Listen to the music of the night …

What’s in the picture(s)
Sh2-173 CAS The Phantom of the Opera Nebula - https://it.wikipedia.org/wiki/Sh2-173
Quote “SH2-173 is a HII region with a diameter of 77 light years, approximately 8800 light-years away from Earth. It is located in the constellation of Cassiopeia in the Perseus arm, one of the main arms of our Milky Way.
Due to its resemblance to the masked main charakter of Andrew Lloyd Webbers musical, the nebula is often called the "Phantom of the Opera" nebula”

What was the experience
Once you start looking around Cassiopeia, it’s packed full with ghosts and other outer-worldly spirits (aka nebulae 😉). This one is a Phantom, as a grim mask looking down on us (or looking up depending on the sky orientation 😂)
This is a  faint Ha region that needs a lot of exposure … The first image I had after 1 night of 6 hours was decent, but not good enough. So I packed in a couple of extra nights. Barring the clouds, I came to a total of 10h20min
I also started making flats, although, spanning three nights … it’s a little bit tedious to keep to camera orientation perfectly u touched
Happy with what I’ve learned 🤩 … The Phantom of the Opera is there … inside my mind 😉

How it was done
Scope: TS-94EDPH APO (FL 414mm / 517mm with 0.8x corrector)
Mount: SkyWatcher EQ6R-Pro
Camera: ASI2600MC Pro
Guiding: @zwoasi OAG, ASI290MM, ASIAIR Pro + dither (#1image/10px)
Filter: Optolong L-Extreme
Resolution: 1,87”/pixel, FoV 235’
Moon: 96%(-), Bortle 5/6 SQM 19.60
Photons:  Gain 100 -10c 600s 62x (41+11+10)
Darks 30x / Flats 60x
Processing: PixInsight (Mac)

What have I learned from this
I was lucky to be able to leave the scope outsides with a gizmo cover, for 3 nights in a row. Covering/uncovering touches the image train, but I did manage to get the orientation spot on again each night, as I want to avoid cropping as much as possible.
Although I had flats for each sueparate night(morning), I haven’t figured out how I can tell pixInsight to use each set with the respective lights (using the WeightedBatchPreprocessing script - or should I run calibration separately for each set)
I continue to notice that the L-Extreme is causing a blue shell around bright stars with the long exposures … maybe it’s time to search for another filter …
Happy with the result …. 🤩

Clear Skies everybody! 🤩✨🔭

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Astrobin: https://www.astrobin.com/users/WCA65/