Link to inverted images
Ou 1 (PNG 151.0-00.4) was discovered by Nicolas Outters in 2009 as he reviewed a narrowband image he had taken of NGC 1491 and noticed a faint spot. The object, along with several other PN candidates discovered by amateurs, was described in a 2012 paper which concluded that the object is likely an HII region, but left the ultimate determination to spectroscopic imaging of the potential central star. In a February 2022 note to the HASH database of planetary nebulae, Quentin Parker reported that the Gran Telescopio Canarias has now done that spectroscopy, and concluded that the OIII and NII signatures and the presence of a blue central star (much too faint to show in my image) indicate that Ou 1 is indeed a PN.
The object clearly has an OIII signature, although it’s very faint and only surrounds the core region. In Ha, it also has a peculiar double tail somewhat reminiscent of HFG 1.
Exposure: Total exposure time 20.7 hours, 28:28 x 20 minutes Ha:OIII and 44:44:44 x 2 minutes LRGB. All bin 1x1. Data collected in January and February of 2022.
Light pollution: SQM ~18.38 (Bortle 7-8, NELM at zenith about 4.5, Red/white zone border.)
Seeing: FWHM of integrated Ha 2.4 arcsec, OIII 2.2 arcsecs
Image scale at capture: 0.6 arcsecs/pixel = f/5.7
Scale of presentation: 1.5 arcsecs/pixel (40% of original 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: ASTAP, 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, Photoshop CS2
Processing Workflow by Workspace in PixInsight 1.8.9:
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 Crop
Dynamic Background Extraction
3. Narrowband Linear Processing
No deconvolution on these images
4. Narrowband Stretching
Histo Trans x 2
Curves Trans
TGV Denoise
Aggressive Multiscale Median Transform (with an inverted luminance mask) to remove background lumpiness
PixelMath: Ha + OIII – 0.15 (the background level of the OIII image). This way the resulting superluminance image was pure Ha, except for the OIII boost to the core of the PN
5. RGB Linear Processing
Photometric Color Calibration, using Average Spiral Galaxy white reference
6. RGB Stretching
Histo Trans x 2
Boost color saturation with Curves
Histo Trans
Curves Trans
StarNet v2 to create a star mask => Stars Image
7. Color Combination
Color for Nebula:
PixelMath to blend stretched narrowband images, using Ludo’s Dynamic Narrowband formula
Curves to brighten and saturate
StarNet v2 to remove stars => Nebula Image
LRGB, using superluminance image as the luminance layer on the Nebula Image
8. Merge Nebula and Stars
PixelMath to add Stars Image to Nebula Image using the formula ((1-$T)*(Stars Image))+$T
Curves to brighten and increase saturation
9. Final
Final Curves Transformation
ICC Profile Transform to sRGB
Resample at 40% scale
Save as JPG
