My fight with an image

[fwm891]

I collected the data for this image at the end of last month and it comprises 18x 300 second sub frames through each: Askar D1 (Ha/OIII) and D2 (SII/OIII) each circa 6nm passbands. The scopes: Askar 120 APO's mounted on an iOptron CEM60, cameras ASI 2600 MC Pro & Duo, cooled to -10° C. The 120's were fitted with a x1 field flatteners.

When I started processing this set of subs I decided I would just put them all together and run them through PI: Combined channel debayer, star align using just one of the subs so they all aligned, integrate all together and out would pop my image.... Well yes it did but with no OIII visible in the combination. So Mk 1 didn't work. Plan 2: I had all the subs star aligned so I would simply integrate as two separate sets: a D1 set (Ha/OIII) and a D2 set (SII/OIII) process each set for colour, contrast etc., and recombine with PixelMath. No. Almost exactly the same with perhaps a 'hint' of OIII but nothing convincing.

So next it was doing something I've been putting off for a while - downloading the Gaia star catalogues to go with SPCC and the Image Solver script.

Keeping the images in a linear state was the most difficult bit for me as I like to tinker as I go along. So the images below show the final stages of the image.

Generating the starless Ha/OIII and starless SII/OIII backgrounds using the D1 and D2 subs, applying SPCC before they were treated to a dose of BXT and star removal to generate the starless frames. Graduation Correction on each of the starless images removed some uneven edges before applying Curves Transformation and Saturation to enhance colour and contrast to the two images. SCNR was applied to the Starfield and a light saturation increase, before it and the two starless images were merged together with PixelMath. I now apply multiplication factors to each image in PM rather than a percentage. Both the starless images were multiplied by x0.5 and the starfield by x0.65. I could perhaps have enhanced the OIII by using a lower x0.45 factor but I'm happy with the result (atm!)....

My PixelMath entry: (HaOIII_Starless*0.5)+(SIIOIII_Starless*0.5)+(SIIOIII_Stars*0.65)  small changes to the decimal places make quite a difference, especially with the star overlay appearance.

So from now on I guess it's use SPCC, and that probably means a revisit to some older images too!

Keep it linear folks!!!

 

 

Edited October 2 by fwm891
Text & image added

[CraigT82]

Very nice images, sounds like you spent a long time in front of the monitor!