Sh2-82 Little Cocoon Nebula

Astrophotography: share your photos & discuss techniques
User avatar
menardre
Vice President
Posts: 886
Joined: Tue Jan 17, 2012 6:09 pm

Sh2-82 Little Cocoon Nebula

Unread post by menardre »

Last night I decided to try what turned out to be a difficult target. Sharpless 2-82 (Sh2-82) is also known as the 'The Cocoon Nebula' or the 'Little Trifid Nebula'. It is a small emission nebula in Sagitta. I found this object while looking through one of my favorite books, "The Night Sky: Observer's Guide". It is a fairly large but very dim object. Its is large enough that no cropping is necessary.

What made this difficult was the dimness of the nebula. I used my 11 inch SCT and ZWO ASI2600 camera set of 0 deg C gain of 100 and binned 2x2. SVX130 and ZWO ASI290 were used for autoguiding with PHD2. SGP managed all of the hardware and the meridian flip. I started with a 2 minute exposure, but could see no trace of the nebula. So I increased the exposure to 4 minutes and increased the stretch to 'high'. Even with the increase, I could still not see any trace of the nebula. I use platesolve to find objects and compared the platesolve to on-line images of SH2-82 -- and determined I had the correct location. So I proceed to image Sh2-82. I started imaging around 8:50 PM and finished around 3:14AM. I took a total of 92 images with 52 flats (0.15 sec). By that time the Moon had risen and the sky was much brighter. I checked on progress throughout the night and found that when the sky got darker, I could just barely make out the nebula.
I processed with PixInsight. This time I tried processing with both star reduction techniques and without star reduction techniques. The image below is without any star reduction, since using star reduction minimizes the impact of the dust lane.

Roger
SH2-82 Nebula.jpg
SH2-82 Nebula.jpg (4.32 MiB) Viewed 393 times
Roger M.
Celestron CPC1100 EDGE, Stellarvue 130T refractor dual mounted on iOptron CEM120 on permanent pier mounted in Observatory. Imaging camera ZWO ASI2600 OSC, guide camera Lodestar or ZWO ASI290MM.
User avatar
Pete
Astro Day Coordinator
Posts: 3999
Joined: Fri Jun 13, 2003 9:03 pm

Re: Sh2-82 Little Cocoon Nebula

Unread post by Pete »

Looks more like the question mark nebula to me Rog. I've found the same thing with star reduction - it wipes out the fainter parts of objects. Am still experimenting with the possibility that doing the size reduction first might be less harmful.
Pete P.
User avatar
menardre
Vice President
Posts: 886
Joined: Tue Jan 17, 2012 6:09 pm

Re: Sh2-82 Little Cocoon Nebula

Unread post by menardre »

Pete

I agree that sometimes star reduction wipes out some details in nebula. I like to use star reduction for galaxies and clusters where I can make the object stand out against the background. I also sometimes use it with a feature mask so that only the stars are reduced, not the 'feature'.

Sometimes I try both methods and see which I like best. I have even found cases where I like both, but for different reasons so I keep both.

Roger
Roger M.
Celestron CPC1100 EDGE, Stellarvue 130T refractor dual mounted on iOptron CEM120 on permanent pier mounted in Observatory. Imaging camera ZWO ASI2600 OSC, guide camera Lodestar or ZWO ASI290MM.
Post Reply