Second clear night in row until around midnight so a good 6 hours of astronomical dark available here in the UK. Looking around Orion for something a little less obvious I thought I would have a go at NGC 2174, the Monkey Head nebula. It is formally within Orion but as you can see from the map below taken from Astrometry.Net its pretty close to Gemini.
A busy area for stars this nebula is away from the madness within the tunic of Orion seemingly just floating among them in isolation.
It is another emission nebula around 6400 light years away. The stars within the head are part of an Open Cluster (NGC 2175), these young stars are quite energetic radiating stellar winds which blow the nebula gas away so you do not get the same sort of complex dust structures in some other nebula.
Capture
2023-01-16
Exposure at gain 100/ Offset 40, 300s at -10ºC, using the Optolong L-Enhance Filter and my ZWO ASI533MC Pro camera.
Lights - 61 (5h5m total exposure)
Dark Flats - 30
Flats - 30 (taken using a Trace Light Box)
Pre-Processing
Tried the automated Siril Preprocessing flow (as per my Siril based Processing instructions), however Flats are still causing me exposure variance which is upsetting Siril's rejection algorithms. Therefore I reverted to manually running and threw out 3 of the Flats that were causing problems (Median value not consistent with other flats taken).
Manually processed in Siril as per my Pre-processing workflow.
I manually rejected on the basis of FWHM 9 lights - passing clouds and very early in the evening subject was low to the horizon making seeing more difficult.
Out of 61 lights I was left with 52 for a total integration time of 4h20m.
Post Processing
Siril
Crop - minor to remove 16 pixel border, snipping off the stacking artefacts
Background Gradient (RBF) - made a big change to the intensity of data across the 3 channels
Colour Calibration Photometry
Deconvolution, Kernal size of 0.8
Asinh Stretch - 3 iterations with stretches of (30,10,4)
Histogram Stretch - auto-stretched
Starless and Stars created using Siril Pixel Maths and Starnet++.
Once we have a TIFF (16 bit version) of Starless move into PS.
At this point I had this stacked image.
I used my usual Photoshop workflow the only notable points while going through this was that during the false luminance generation I was careful not to overly darken the image.
Another 'made myself smile' moment was that for much of the processing I was working with my Monkey upside down. It has come off the camera in that orientation and I had convinced myself that I could see the monkey albeit I did think to myself that it looked more like an Ape! After looking at some other images of this subject I realised and rotated both it and the Stars by 180º - the monkey revealed it self!
The starless and Stars image as combined in Photoshop rather than using Pixel Maths in Siril.
Results
Update on 2023-02-20
Just to prove I keep an eye on what some of my my other astro'ers are doing I noticed that some had actually got the Monkey head in what I would suggest is the Ape position! So below is what I would say is the Monkey... followed by the Ape!
I am pretty happy with this image, close up the is some noise around the wispy hair on the top of his head and I think that would be cleared up with more integration time.
Perhaps one or two more nights this week of clear skies.... what next!
Clear Skies All.