Seeing more of the lion nebula

[timh]

A work in progress to try and fit more of SH2-132 into a single image. The plan is to accumulate more data to try and increase SNR. Angling the camera and using the 0.9X SW flattener/ reducer to bring the F 5.0 SW PDS200 down to F 4.5 (1.05 arcsec/ pixel) just about fits most of the nebula in.

So far ~ 83 x 40s (UHC Astronomik filter) OSC AS1294 MC frames, 80 x 3 min OIII frames (6 nm Astronomik) and 60 x 3 min HA (7 nm Ooptolong) AS1294 MM frames all captured using Sharcap 4 and guided using PHD2 on a CEM70 mount. A useful feature of Sharpcap here was the ability to reliably centre this particular field.

I was pleased to note here that the alignment, tilt and spacing seems to have been pretty good with near round stars right to the edge of the field - which speaks well of the performance of the SW 0.9X reducer/ flattener.

I think that this is a really interesting object. The two main drivers of ionisation are the Wolf Rayet stars HD211853 (WR153ab) with what appears to be a peculiar near straight ray of OIII - possibly part of a stellar wind-driven blue ring and - on the tail side- HD211564 which is surrounded by an expanding shell of - unusually - predominantly blue OIII light. Similar to in planetary nebulae the stellar electron temperature must be high enough to drive such high emission of OIII but the scale of these Wolf Rayet-driven OIII nebulae appears far greater - judged from their angular size at a distance of 15,000 ly maybe some 80-150ly across - still hot and still expanding?

Tim

[Menno555]

Great capture so far Tim! Looking forward to the more data styacks.
I did a quick check with captures from around 1953 with the Palomar Telescope but no visible expansion, just some proper motion stars.

Menno

[timh]

Thanks Menno

Final version here. https://www.astrobin.com/y3uet3/B/?nc=user


A suitable dark night to complete the picture came along quicker than I thought (weather here dominated by the atlantic and almost completely unpredictable from night to night) - it does mean taking a risk with leaving the equipment out at night and keeping a close eye on the possibility of rain.

Overall about 5h of HA and 6h of OIII beyond which perhaps the law of diminishing returns applies. In my own opinion I don't think that SII would add all that much. I like SII in HII region type nebulae because it is a marker of the ionization edge and along with OIII marking the core provides a kind of 3 D perpective. However I don't think that would apply to these great WR star debris-blown bubbles - OOH seemed the better and more naturalistic palette for this one.

Tim