C/2022 E3 Comet passing by NGC1647 - First light ASI2600MMPro with new Chroma filters

Original Post - 02-19-2023:

First light for my new ASI2600MMPro, 36mm Chroma filter set with wheel, OAG-L, and ASI174MM Mini guide camera. I had purchased the new equipment in preparation for a new WO FLT 132 with feathertouch focuser and iOptron HAE43EC mount, but still waiting on those to come available. In the meantime, I have been working the new setup with my WO GT81iv.

It has been 2 months waiting for some open sky to try out the new gear and my first outing didn't go well as I was adjusting the OAG and guide camera with only a few hours of available sky. I had also been waiting to get a shot of the 50K year comet, so it ended up being first light for the new gear.

I had to throw out half the subs as I didn't think about the OAG setup needing polar aligned after camera rotation. I had applied a 45 degree rotation to get NGC1647 in the shot with the comet relatively centered. In the small previews, I didn't really notice the PHD2 compensating for this until later review on my processing machine. Needless to say, I was able to make things work, but the stars are definitely far from my normal standards.

Target Workflow (R,G,B subs):
- No drizzle utilized

All subs:
-----------

Blink
- Review all subs and remove visually bad frames (none this time)

WBPP
- Cosmetic Correction Applied
- Pedestal added to avoid clipping in later processes = 800DN

Comet Processing:
-----------

Comet Align
- All subs regardless of filter processed together

StarXTerminator
- Uncheck all options
- Select 'Process Batch'
- Save all to starless folder

Image Integration
- R, G, B comet aligned subs separately
- Winsorized Sigma Clipping
- Scale + Zero Offset

Linear Fit
- use Statistics to find the lowest channel Median value for reference sub = R

LRGB Combination
- Uncheck L channel and load R, G, B comet aligned integrations
- Check Chrominance Noise Reduction
- Save as starless

DBE
- Apply Subtraction with Tolerance 2.5, Smoothing Factor = 0.65

NoiseXTerminator
- Apply with Defaults

Generalized Hyperbolic Stretch on starless
- Multiple iterations to zero in and finalize with Linear at end

Exponential Transformation
- 0.7 amount on single interation

Curves Transformation
- Adjust top and bottom ranges to lighten comet center and darken background
- Save as final starless image for recombination later on

Starfield Processing:
----------

WBPP
- Load Cosmetic Corrected light subs with previous WBPP settings intact
- Check Image Integration
- Check Astrometric Solution
- Check Local Normalization (Automatic)
- Check Image Integration

Linear Fit
- use Statistics to find the lowest channel Median value for reference sub = R

LRGB Combination
- Uncheck L channel and load R, G, B from master integration folders that WBPP generated
- Uncheck Chrominance Noise Reduction
- Save as 'RGB_Stars'

DBE
- Apply Subtraction with Tolerance 2.5, Smoothing Factor = 0.65

Image Solver Script
- Search and set target from database = NGC1647 if default run fails

Spectrophotometric Color Calibration
- White Ref = Average Spiral Galaxy
- QE Curve = IMX571
- Check Narrowband filters mode
- Set Wavelengths (Chroma R, G, B)
- Make very small background preview
- Set Background Neutralization->Region of Interest->From Preview->Select the background preview

StarXTerminator
- Check 'Generate Star Image'
- Generate stars from 'RGB_Stars' image and save as 'stars'

ArcsinhStretch
- Partial stretch 'stars' image until stars are about 50% final desired brightness

Generalized Hyperbolic Stretch on 'stars' image
- Multiple iterations to zero in and finalize
- Linear not needed do to ArcsinhStretch

Final Image Processing:
----------

Extract CIE Luminance from 'stars'
- for use in later steps
- save as 'stars_L'

Pixel Math to Re-add Stars
- apply range mask to protect core of comet
- Formula = ~((~HOO_Starless)*(~HOO_Stars_masked))

Dynamic Crop
- Trim to preference

Curves Transformation
- Apply 'stars_L' and range masks as needed
- Adjust contrast and colors to taste
- Save final and JPG for upload

Sessions

Total Integration Time:

Feb. 12, 2023 - 22 * 90.0 seconds
Chroma Blue 36 mm
Feb. 12, 2023 - 30 * 90.0 seconds
Chroma Green 36 mm
Feb. 12, 2023 - 19 * 90.0 seconds
Chroma Red 36 mm

Catalogues

New General Catalogue

Targets

NGC1647

Gear

Telescope: William Optics Gran Turismo 81 IV
Camera: ZWO ASI2600MM
Mount: Sky-Watcher EQ6R-Pro