11/03/2023 – The Soap Bubble Nebula

OK OK OK… So this is really cool… well at least I think so… so very cool. The other night when I was EAA observing the Crescent Nebula and broadcasting on Night Skies Network, a couple of the folks that joined the broadcast suggested I should try for the Soap Bubble Nebula. The Soap Bubble Nebula? I had not heard of that one before.

The Soap Bubble Nebula (PN G075.5+01.7) is a faint planetary nebula in the constellation of Cygnus. The Soap Bubble Nebula was discovered by amateur astronomer Dave Jurasevich on July 6th, 2008 using an Astro-Physics 160 mm refractor telescope. It is very faint and very difficult to capture (this is what makes it really cool, so very cool).

Friday night I decided to give the Soap Bubble Nebula a try.

Primary (Imaging) Secondary (Guiding)
Scope: SVBONY SV503 102ED, UA Field Flattener
Filter: ZWO Duo-band Filter
Camera: ZWO ASI294 MC Pro, Cooled to -10 C
Focuser: ZWO EAF
Mount: Sky Watcher EQ6-R Pro
Scope: SVBONY SV106 60mm Guide Scope
Camera: Orion Star Shooter Autoguider (OSSAG)

I was never able to resolve it in SharpCap live stack, but at around 90 minutes in I loaded up what I had in Siril and stacked the frames… I had to stretch the histogram a lot but I found it!!! I was so excited to actually be able to see this faint object.

I ended up capturing 91 x 120 second exposures, so just over 3 hours of data, of the Soap Bubble Nebula at 121 gain, 8 offset, and bin 2×2. I would have collected a bit more light during the session, but I had some issues with exposure timeouts on the camera. I reset the camera and indiserver once and was able to get another hours worth of data, but when it timed out the second time I decide to call it a night.

I extracted and stacked the Ha and OIII with a Siril script (OSC_Extract_HaOIII.ssf). Then recombined the Ha and OIII data into RGB using Pixel Math (the formulas I used are below). I had to stretch the histogram pretty aggressively to get the bubble but… there it is… The Soap Bubble Nebula
The Soap Bubble Nebula - 91 x 120 seconds - SV503 102 ED, ASI294MC Pro, ZWO Duo-Band Filter - Processed in Siril
Having trouble finding it? Here is a directlink to the full Soap Bubble Nebula image, right click and open in new tab to view outside the light box. The Soap Bubble is pretty much dead center. The bright nebula at the top, just peaking over the left of top center edge is the Crescent Nebula (NGC 6888).

Still can’t find it? Here is the same image above with the Soap Bubble circled.
Soap Bubble Nebula - 11/03/2023 - Annotated
It is very faint. You would more than likely overlook it if you were not looking for it or if you did not know it was suppose to be there. This is probably why the Soap Bubble Nebula was not even discovered until 2008. I plan to gather some more light from the Soap Bubble but this is very cool start (IMHO).

Here is the pixel math I used in Siril to combine the Ha and OIII data. I tried a bunch of different formulas and this is the combination I thought worked best.
R = Ha*.91 + OIII*.09
G = OIII*.93 + Ha*.07
B = OIII*.97 + Ha*.03

How did I come up with that? I found it in this post on CloudyNights.com and I was happy with the output.

Anyway hope to get some more time on it the next few nights. I will also keep playing with the post-processing in Siril to see what I can see.

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