The week started here with a grim weather forecast, rain, cloud and winds taking us from October to November. Not exactly a surprise here in the UK, but there was a glimmer of clear sky on Sunday 30th Oct. I have fancied revisiting NGC 1499 the California Nebula and so I planned and was set up, polar aligned and yes just ready to capture and clouds swept over like they knew!
This failed imaging session got me thinking about whether I should revise old data and try reprocessing with the new workflow to see what improvements I have made. Looking through my images I did have a single night on the California back in January 19th this year. In Jan this year I was using Deep Sky Stacker and Photoshop. Now it's Siril, Starless processing before heading into Photoshop. If you are interested here's the link to read all about my Post Processing workflow.
On the border of Perseus and Auriga, NGC 1499 or the California nebula named after its resemblance to the American state. Around 1,000 light years away this is fairly large object 2.5º long, although technically this is a magnitude 6 object because it spread over such a wide area it is a very difficult object to see visually.
It is glowing because of the large O7 star Xi Persei or Menkib. It is glowing in Hß wavelength and is one of the few stars of this type that can be seen with the naked eye.
The plate solve of the image show Menkib, also IC2027 which is an Elliptical Galaxy and the star 49 Perseus. This is a dying giant star around 147 light years away
Capture
2022-01-19
Exposure at ISO800, 120s using the Optolong L-Enhance Filter
Lights - 92
Darks - 30
Flats - 30
Pre-Processing
Using my auto preprocessing scripts, with the following filters post registration:-
FWHM - 3.5
Weighted FWHM - 5
Roundness - 0.8
Out of the 92 images (3h4m ) this filtering lefts me with 74 (2h28m) lights. They were capture at 120s ISO800 using the Optolong L-Enhance filter.
This started out as being casually curious about the re-processing result so I did not "blink" the images I just used the filters as stated.
Stacked 74 * 2m -Total Integration Time = 2h28m
Post Processing (Nov 1, 2022)
Siril
Crop - fairly minor to remove one corner of elongated stars and snip off the stacking artefacts
Rotate 180 - to orientate like the namesake American State.
Background Gradient
Colour Calibration Photometry
Deconvolution, Kernal size of 0.8
Asinh Stretch - 3 iterations with stretches of (30,30,5)
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 Processing
Levels and Curves - sympathetic to keeping the red channel dominant - this is very much a Hydrogen region with very little Green or Blue data.
Raw - Highlights and Contrast
Raw - Texture
Raw - Clarity
Raw - Colour Contrast - Pushing reds to deeper reds using the red hue, also pushing the oragsse to Yellow hue this brought out more 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 Photoshop processed TIFF file using the formulae (starless+(0.8*stars)).
Created JPG version for my Instagram and Twitter feeds.
For comparison, using the same data I created this image with basic Photoshop skills I had back in Jan 2022, I believe I have managed to not only make a more dramatic image but also find some detail that was not apparent in this previous image.
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