NGC 7762

Ngc7822 153x420+52x360+155x420+52x360+168x420+80x360 4556m 76h.jpg
Autor/Urheber: Ram samudrala, Lizenz: CC BY 4.0
~76 hours nebula and open cluster B59/Ced214/LBN589/NGC7762/NGC7822/Sh2-171 (c-sho).

Total integration: ~76 hours/4556 minutes = (153x7m + 52x6m for S2) + (155x7m + 72x6m for Ha) + (168x7m + 80x6m for O3)

Camera: QHY163M (16mp mono) CMOS cooled to -15 degrees C. Telescope: Stellarvue SV70T triplet apochromat refractor @ f/4.8. Reducer: SFFR70-APO Mount: Paramount MyT. Filters: Astrodon 5nm Ha, 3nm O3, 3nm S2. Software: Sharpcap, PixInsight.

http://ram.org/ramblings/cosmos/

NGC7822 is the designation given to young star forming complex (Berkeley 59) in the constellation Cepheus, whose surrounding environment has a distinctive skull-like appearance. The emission nebula (core region) is Sharpless 171 aka Cederalbad 214 and the wider field object with the loop/ear-like structure consists of both NGC7822 and the cluster of stars to the upper right that look like little white flecks of paint is NGC7762 (the ear within the ear). There is more to this nebula that goes down below and fleshes out the skeleton shape, but obviously doesn't fit within my FOV.

The emission nebula contains examples of objects known a "pillars of creation", active star forming regions that use the material in the nebula to shape the overall structures until there is no more raw material left creating a cavity in the middle (which is why some of these nebulae may start to look the same). The region is 3000 light years away, so it probably is still active. The field of view spans over 40 light years. The region also contains a supernova remnant somewhere (G118.3+0.4.

As of now, this is the target I've spent the most time on, taking 17 nights to do it all over a month (largely automated of course, but still) to end up with ~76 hours of useful data. It was a tough target for a variety of reasons but because the surrounding loop region is fainter than the central core, extra time was necessary to obtain some contrast and detail. Unlike with relatively brighter nebulae, where a few hours with each is enough and diminishing return sets in fast, I found that the longer the total exposure, the greater the contrast and detail I was able to obtain. I am confident that what you see (particularly in the nominally processed versions D and E) is what you get if you go deeper with this target---there are a lot of dark regions that are real.

An additional frustrating thorn in my side was clouds. Multiple forecasts would state "clear", I would set up, go inside and then the clouds would come and go. There were few days of data collection where this issue didn't exist but fortunately PixInsight's image integration worked its magic and was able to register all but a few frames (though a few hours worth were weighted very low and this is after manually discarding over 50 frames that were completely cloudy). I did some integrations ignoring the worst frames but the difference was so tiny (and it was arguable as to which version was better) that I decided to use all the data I collected as long as the software didn't mind. Finally, another milestone with these images is that this is the first time I didn't rely on Photoshop to do the Hubble palette tweaking, relying only on PixInsight to do it.