As December progresses the fabulous constellation of Orion and Monoceros become more accessible to my location in the UK. My southerly horizon is somewhat obscured by mine and neighbouring houses and therefore by around midnight to 1 am I lose these objects, this together with giving them chance to rise sufficiently to get out of any easterly light dome means I have 3 to 4 hours a night to grab images. Given Christmas was 11 days away I thought I would turn my new camera to an object I have not tried imaging before, the Christmas Tree Cluster. A number of other objects and designations exist, the formal catalogue number being NGC 2264 which is actually the same number attributed to both the Cone and the Christmas Tree. I had two cold nights, clear and frosty with a Moon that would not rise for a few hours, so on the nights of 14th Dec and 15th Dec I gave my new camera (533 MC Pro) some exercise.
This nebulous region lies within the Unicorn Constellation, Monoceros, the same constellation that the spectacular Rosette nebula lies, possibly this is one of the reasons that other than the Christmas time of year this object is overlooked.
Monoceros is one of the 'modern' day constellations dating from around the 17th century, it's faint and as with many of the constellations difficult to imagine a Unicorn formed by the pattern of stars.
Other less formal objects within this field are the Snowflake Cluster and Fox Fur nebula. All the objects are part of the large emission nebulosity around 2700 light years away.
I have used the red channel of the stacked final image for annotation purposes as most of the objects push out more Hydrogen emission that anything else.
Starting at the top of the tree is the Cone Nebula a dense region of gas and dust. Just below and to the right is the Snowflake Nebula, at my focal length and with the exposure I have captured so far this indistinct in my image, may be more time would solve this.
The Christmas Tree open cluster is shown with my dotted line linking the main stars. Towards the bottom right of the image is the Fox Fur Nebula again more focal length and exposure time would be required to pick out more detail. Finally, one of the stars of the Monoceros constallation (S) makes up the trunk of the tree.
Capture
2022-12-14
With gain of 100 and Offset of 40, running at -10º C and 300 sec exposures using the Optolong L-Enhance Filter
Lights - 43
Darks - master created at -10ºC from 30 Dark Frames of 300s.
Flats - 30 created at 50% histogram, 6.91sec taken at -10ºC
Flat Darks - 30 6.91sec taken at -10ºC
I have have seen some debate regarding the use of Bias vs Dark Flats as part of calibration. I used both methods and the final versions of the image where indisguishable from one another. Even looking at the overall statistics of images showed very little difference when generating a master flats. Therefore I have taken the decision to use Dark Flats.
2022-12-15
With gain of 100 and Offset of 40, running at -10º C and 300 sec exposures using the Optolong L-Enhance Filter
Lights - 34
Darks - master created at -10ºC from 30 Dark Frames of 300s.
Flats - 30 created at 50% histogram, 6.85sec taken at -10ºC
Flat Darks - 30 6.85sec taken at -10ºC
Pre-Processing
Although 77 lights were taken some wFWHM rejections of 5 and some FWHM rejections of 3.5 left me with total of 63 lights across the two nights.
26*5m= 5h15m of exposure..
Post Processing
Siril
After registration of all images (before the selection of the best 25) I ran a background extraction process on all registered images using a simple 1-order Polynomial model (straightforward Siril option). This was performed as there was a significant moon that evening and the fact that a side of pier (east->west) was performed meant that background extraction did not work well on the final image.
Crop - minor to remove stacking artefacts
Colour Calibration Photometry
Deconvolution, Kernal size of 0.9
Asinh Stretch - 3 iterations with stretches of (30,10,2)
Histogram Stretch
Green Noise Removal
Starless and Stars created using Siril Pixel Maths and Starnet++.
Once we have a TIFF (16 bit version) of Starless move into PS.
Photoshop (PS) Processing
Levels & Curves - Careful here not to overly balance the channels, doing this initially resulted in a rather bland yellow fire not the raging red this nebula is known for.
Raw - Highlights and Contrast
Raw - Texture
Raw - Clarity
Raw - Colour Contrast
Raw - Noise Reduction
Raw - Saturation and Vibrancy and Shadow
Create FIT version of TIFF file output from PS using Siril
Once back from PS then Pixel Math Add the Stars back into the FIT version of the PS processed TIFF file using the formulae (starless+(0.9*stars)).
Created JPG version.
Final Thoughts
More integration - it is faint and to do justice to this interesting group of objects I really need more signal. That said the main reason I chose this object was to try and get enough imaging to wish everyone a Merry Christmas and Happy New Year. Clear skies everyone.
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