M31_Andromeda_18Nov23_v2

Target: M31 Andromeda.

I've imaged Andromeda a hand full of times as I've acquired new equipment and/or processing skills. My last image was shot at 400mm, this time I did a 3 panel mosaic at 600mm (wasn't positive I could do 2 panel). The objective was to achieve higher resolution and shoot using both a broadband light pollution filter and dual narrow-band filter to capture more Ha.

 

Gear:

Mount: ZWO AM5

Main Cam: ZWO ASI294MC Pro @ gain 121 and 14F

Guide Cam: ZWO ASI120MM Mini with ZWO 30mm f/4 scope

Lens: Sigma 150-600 @ 575

Filter: Antlia ALP-T 5nm Ha and Oiii

Filter: Baader Moon and Sky Glow

 

Acquisition:

BB Light frames: Best 2hrs of 2 minute subs

NB LIght frames: Best 42min of 3 minute subs (needed more)

Sessions: 15-Nov-23, 18-Nov-23

Location: Houston Colorado County and Waller County, Texas

Bortle: 4/5 and 5/6

Moon: 35%, 90degrees off target for most of the 18th

 

Processing NB

• PI - WBPP -

• Grouping key = M31 (Both Pre and Post)

• Registration - Auto by M31

• GraXpert background extraction on each panel

• PI - assemble mosaic

• Mosaic by Coordinates

• Gradient Merge Mosaic

• PI Dynamic Crop (save process)

• PI Image Solver

 

Processing BB

• PI - WBPP -

• Grouping key = M31 (Both Pre and Post)

• Registration - Auto by M31

• GraXpert background extraction on each panel

• PI - assemble mosaic

• Mosaic by Coordinates

• Gradient Merge Mosaic

• PI Dynamic Crop

• PI Image Solver

 

Processing adding the Ha and recombining to RGB

• PI Register the NB and BB

• PI Split channels of NB - keep only the red - relabel ha

• PI Split channels of BB - keep all three - relabel red, green, blue

• PI Remove Stars from ha image, no need to create star image

• PI Remove Stars from red image, create a star image, un-screen them

• PI Open ha starless, Open Pixel Math to create new image-

• ((ha*85)-(red*5))/(85-5)

• Where 5 is the bandwidth of filter

• Can reduce the 85 if ha too strong

• Rename new_ha

• PI Make a clone of new_ha

• PI Open STF and clip the shadows to really isolate the ha nebula

• PI Open Histogram Transformation move STF to HT and apply to new_ha_clone

• PI Range Selection to create a mask in order to protect the red

• PI Open red channel and apply the mask

• PI Open Pixel Math to add ha

• $T+(new_ha-Med(new_ha))*8

• 8 is a boost number

• Replace target image

• PI Open Pixel Math = red+red_stars - replace image

• PI Put together channel into RGB

 

Normal Post Processing

• SPCC

• SCNR

• BTX

• NTX

• STX - un-screen stars

• Stretch starless using GHS script

• Starless curves and color adjustments

• Unsharp mask, enhance dark structures

• Adding Stars back in

• Create a mask using ACNR that is hardly protecting galaxy, this will de-emphasize stars on top of galaxy

• Re-screen stars with Pixel Math

• Emphasizing larger stars to "bring them forward"

• Clone stars image, use GHS to more brighten, but slightly enlarge them

• Use Range Selection to create a mask limiting to ones you want to emphasize apply to rgb image with original stars

• Re-screen stars with Pixel Math

Photoshop - final curves, vibrance on stars, watermark

Done