Adding more data to previous sessions is something that becomes a regular occurrence, why start from scratch for each target? The key is to frame the object as near as possible and ideally get the rotation the same. Three weeks later means Auriga is up earlier and is a higher target in the night sky. When you are into this hobby things like that and the changes to moon and sun setting which to most people is almost imperceptible becomes very obvious and really highlights the dynamics of the solar system. The only thing this evening that will shorten the imaging time will be the awful dose of 'flu' I am carrying. Take a look at my earlier session at the beginning of November for the details of the objects. No moon this evening of 23rd November, starting temperature of 8° finished at 6.7°. This blog will mostly focus on the capture details for this session and the proceed processing of this plus the first session of 3rd November. Camparing quality of the data.
Capture
2022-11-03
Exposure at ISO800, 240s using the Optolong L-Enhance Filter
Lights - 86
Darks - 30
Flats - 30
The Darks here where made up of 10 taken just before starting imaging at 7.9ºC and 20 at finish of processing at 4.5ºC. Dark calibration all about trying to take account of the thermal current on the sensor I made the decision to include both. My intention here is to start build up a library of Darks at given temperatures, I did this on this occasion during the evening while waiting for the target to get sufficiently over my horizon.
2022-11-23
Exposure at ISO800, 240s using the Optolong L-Enhance Filter
Lights - 51
Darks - taken at end of session at 6.70°
Flats - 30
Pre-Processing
51 lights taken but the night was blustery, lots of frames discarded due to clouds and rain paused the sequence after 30 minutes. In the end using the same filters of FWHM, Roundness and Weighted FWHM (4, 0.8, 5), then manually blinked through removing shots that showed cloud.
In total I processed 67 from the 3rd November plus 27 from this evening), 93*4m = 6h12m
Post Processing
Siril
Crop - fairly minor to remove one corner of elongated stars and snip off the stacking artefacts
Rotate 180 - I like my flames rising!
Background Gradient - made a big difference using the RBF method, this is probably Moon related.
Colour Calibration Photometry
Deconvolution, Kernal size of 1.0
Asinh Stretch - 3 iterations with stretches of (30,30,8)
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+(0.8*stars)).
Created JPG version.
Final image
The following show the previous and now final image.
Final Thoughts
As hopefully you can see, the processing used on this final version was not as aggressive as the previous shot. Looking back I was probably over compensating with saturation because of the lack of data, although I have only added an extra couple of hours I could tell with the processing in Photoshop it was much easier to show fainter details and as such I did not pull the red levels up as severely.
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