I re-processed  some LRGB data of the Fireworks Galaxy from last year captured with the C14 Hyperstar under average seeing conditions. The Fireworks Galaxy is currently a target of the Big Amateur Telescope (BAT). If you want to contribute data for this or other B.A.T. targets or help processing data, you find further information on how to join the B.A.T. on the homepage.

Equipment

ZWO ASI 1600 MM Pro @ -20°C
+ C14 & Starizona Hyperstar v2 @ 675 mm (f/1.9)
+ Baader 2" LRGB filters
+ Celestron EF
+ Tempest Cooler
+ Omegon Dew Heater
+ Astrozap Dew Shield for C 14 Hyperstar
on CGE-Pro mount

Cable managment to mitigate Hyperstar diffraction spikes.

Autoguiding:
Artesky 70 mm Guidscope (f=400 mm)
ZWO ASI 120 MM mini
PhD2 (Multistarguiding)
Dither every 4 subs

light frames:
601 x 30 s (L, gain=75, offset=15)
126 x 30 s (R, gain=75, offset=15)
119 x 30 s (G, gain=75, offset=15)
121 x 30 s (B, gain=75, offset=15)

dark frames:
60 x 30 s

acquired with N.I.N.A.

Average FWHM: 2.1" - 2.9"

Remaining Issues
- requires more RGB data to reduce chrominance noise
- BXT introduced some artifical features in the galaxy
- add high resolution (LI) data < 2"

Post-Processing:

PixInsight

LRGB (linear stage)

- automatic rejection of subs with the subframe selector based on number of stars, FWHM and eccentricity
- manual rejection of bad subs
- image calibration (darks & flats) & image registration with WBPP script,
- NSG for each channel
- dynamic crop
- create undistorted, synthetic star reference frame with Script -> Render -> CatalogStarGenerator
- Star Alignment using Thin Plate Splines and Distortion Correction
- DBE of each channel

RGB (linear stage)

- linear fit of R & G channel wrt B channel
- RGB channel combination
- DBE
- PCC with background neutralization (White reference: Average Spiral Galaxy)
- EZ Soft Stretch (Target Median: 0.2)

L (linear & non-linear stage)

- BXT
- EZ Soft Stretch (Target Median: 0.2)
- HDRMT (number of layers:7, scaling function: Gaussian(11), To lightness, Lightness mask)

LRGB (non-linear stage)

- LRGB combination with chrominance noise reduction
- star removal with SXT
- create and add luminance mask
- color saturation enhancement of the galaxy using curves transformations
- desaturation and darkening of the background
- remove green tint with histogram transformations
- LRGB_MMT: MMT - Bias = 0.1 on layer 4
- Unsharp mask for slight contrast enhancement (StdDev: 5.8, Amount: 0.26)
- remove lum mask
- NXT
- add stars to starless image with pixel math
- create star mask by exctracting L channel from RGB stars
- 2x EZ Star Reduction with star mask
- add star mask
- enhance star color using Color Saturation

Adobe Lightroom

- final contrast, levels, HSL tweaks

Location (Bortle 4): Schwentinental, Germany

- CS Daniel