The squid and the bat (Ou4 and Sh2-129)

Click on the image for a high res version. MOUSE OVER for OIII only. Look also to the OIII only hires and H-alpha only hires.

Sh2-129 (the flying bat) is a faint red emission nebula in Cepheus. I've recorded a few times in H-alpha only and color (Ha+RGB), but I alway wanted to image the extremely faint OIII nebula Ou4 (the squid). Finally I've bought an OIII filter and waited the right month, September. Curiously my previous image of this area was taken 4 years before from the sample place, the Star Party in Saint Barthelemy.
The only way to see the squid nebula is using an OIII filter, and take many hours of exposure. That's really faint! I invester one full night on the two of the star party to collect light in OIII, while the other one was shared between H-alpha, RGB and... clouds. This image finally gained the second place at the photographic competition of the star party.

Technical Data
Optics TEC 140
Focal Length
1011 mm
Focal Ratio f/7.2
Exposure Time Total 12 h, composed of OIII-Ha-RGB 390:150:60:60:60 min (single exp of 30 min for OIII and Ha, and 10 min for RGB)
CCD SBIG STL-11000M @-30C
Location Saint Barthelemy football field (AO, Italian Alps) at 1600 m heigth
7-8 September 2018 (2 nights)
Mount Gemini G-41
Tracking Lodestar on an 80mm f/5 refractor
Temperature and humidity T= (+10 to +7) C, RH=(85 to 100) %
Sky brightness at zenith (with SQM-L) (21.3 to 21.5) mag/arcsec^2
Notes The first night was perfectly clear while about 50% of the second night was clouded.

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