Link to inverted Ha and OIII images
Weinberger 1-2 (PNG 160.5-00.5, PK 160-00.1) was discovered by R. Weinberger in 1977, and seems to have been waiting for a deep image ever since then. I can’t find any detailed images, but it was recorded near the bottom of this image of Sh2-216 by Stephane Zoll. The nebula is magnitude 18.5 and has a diameter of 92 arcseconds, and this article in ApJ calculated a distance of 534 light years. There’s very little else known about this nebula. As the inverted narrowband images show, the Ha signal is much stronger than the OIII. I used only Ha in the color image here.
Exposure: Total exposure time 14.5 hours, 39 x 20 minutes Ha, 30:31:32 x 2 minutes R:G:B. All bin 1x1. Data collected from September to November 2021.
Light pollution: SQM ~18.38 (Bortle 7-8, NELM at zenith about 4.5, Red/white zone border.)
Seeing: FWHM of integrated Ha around 2.2 arcsecs
Image scale at capture: 0.6 arcsecs/pixel = f/5.7
Scale of presentation: 1.2 arcsecs/pixel (50% scale).
Equipment:
Scope: C11 (standard, not Edge) with Celestron 0.63 reducer
Mount: Paramount MX+, connected via ASCOM Telescope Driver 6.1 for TheSkyX, with MKS 5000 driver 6.0.0.0
Camera: SXVR-H694, connected via SX ASCOM driver 6.2.1.17140 (SX 1.2.2 also installed)
Filter wheel: Atik EFW2 with 7x1.25 carousel and Artemis 2.4.3.0 driver
Filters: Astrodon Type IIi LRGB
Rotator: Optec Pyxis 2", connected via Andy Galasso's 0.4 driver (Optec Pyxis Rotator AG)
Focuser: Rigel Systems GCUSB nStep motor with driver version 6.0.7 on stock Celestron focuser
OAG: Orion Thin OAG
Guide cam: Lodestar (first generation). 4 second exposures
Automation SW: Sequence Generator Pro 3.1.0.457
Guide SW: PHD 2.6.7, connected to guide cam via native SXV driver
ASCOM: ASCOM 6.3.0.2831
Platesolving: PlateSolve 2, failover to local Astrometry.net 0.19 server
Collimation: Metaguide 3, using ASI120MM connected via ZWO Direct Show driver 3.0.0.2
Processing Software: Pixinisight, Affinity Photo, Photoshop CS2
Processing Workflow by Workspace in PixInsight 1.8.8:
1. Calibration
Calibration with WeightedBatchPreProcessing with flats and bias, using Cosmetic Correction with a master dark
Blink to preview and reject a few frames
Weighting and registration with WBPP
2. Stack and Mure Denoise
Image Integration on each channel
Mure Denoise on each channel
RGB Combination for RGB frames
Dynamic Background Extraction
No deconvolution was applied to these images
3. Ha Stretching
Histo Trans x 3
Curves Trans
TGVDenoise
Aggressive Multiscale Median Transform (with an inverted luminance mask, so that the effect was not applied to the nebula) to smooth out background
4. RGB Linear Processing
Photometric Color Calibration, using Average Spiral Galaxy white reference
5. RGB Stretching
Histo Trans x 3
Curves
TGVDenoise
Aggressive Multiscale Median Transform (with an inverted luminance mask, so that the effect was not applied to the nebula) to smooth out background
Histo Trans to darken the background
6. Color Combination
StarNet++ on stretched Ha image to remove stars, then convert to RGB
Create range mask to target only the nebula and apply to Ha image
Colorize Ha, using Curves Trans to pull up red and reduce blue and green
In Photoshop, layer colorized Ha into starfield using a mask
7. Background Subtraction
a. Create an image of the background:
1. StarNet++ to create a starless image. I used the spot healing brush in Photoshop to remove the nebula and a few background galaxies.
2. In PS, apply a dust & scratches filter at very low strength (5 pixels) to smooth image so that noise is not removed during the subtraction process
b. Subtract the background image from the original image in Photoshop to remove remaining gradients and any messy clumps in the background, applying an offset so that the background is not pure black
8. Final
Final Histogram Transformation to darken background
ICC Profile Transform to sRGB
Resample at 50% scale
Save as JPG
