Link to inverted images
Abell 62 (PN G047.1-04.2) is a 2.5 arc minute planetary nebula located in Aquila. A recent distance estimate placed it at about 1600 light years away. Cartes du Ciel shows its magnitude as 14.8, though the source of that estimate is not listed. I'm not sure where the central star is. One catalog entry seemed to list a central star at magnitude 18.8, but the star at the exact center of the nebula is yellow. There are several very faint blue stars just a bit off-center.
The object has both Ha and OIII signatures, but the Ha is much stronger and more defined. This image uses Ha as luminance, and for color maps Ha:OIII:(15% Ha + 85% OIII) to R:G:B. Stars are RGB.
There are very few images of this nebula. I found only three amateur images, from 2007 to 2012, and no professional images other than the wide-area sky surveys.
Exposure: Total exposure time about 26 hours, 44:26 x 20 minutes Ha:OIII for the nebula and 26:23:25 R:G:B x 2 minutes for stars. All bin 1x1. Data collected from June to August 2020.
Light pollution: Bortle 7-8 (white zone, NELM about 4.5)
Seeing: Average FWHM of Ha and OIII subs around 2.1 arcsecs
Image scale at capture: 0.6 arcsecs/pixel = f/5.7
Scale of presentation: 0.9 arcsecs/pixel (67% of full 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 IIe 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 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 Crop
3. Narrowband Linear Processing
Dynamic Background Extraction
(No deconvolution on these images)
4. Narrowband Stretching
Histo Trans x 2
Curves Trans
TGV Denoise
MultiscaleMedianTransform for noise reduction, using an inverted and blurred luminance mask
Local Histogram Equalization, using a range mask, to enhance contrast in the nebula
5. RGB Linear Processing
Dynamic Background Extraction
Photometric Color Calibration, using Average Spiral Galaxy white reference
6. RGB Stretching
Histo Trans
Curves
Boost color saturation with additional Curves
7. Color Combination
Combine Ha and OIII in PixelMath using HOO palette to create color nebula image
Shift teal green to blue with Curves Trans
LRGB Combination, using Ha as luminance and HOO for color
8. Star Reduction
I followed Adam Block’s star reduction technique:
StarNet to create “Starless Image”
Extract two copies of luminance from main image, then apply MLT to one to create a rough star mask
Binarize to select only the stars
MorphTrans to enlarge stars
Convolution to blur star edges
Pixel Math: subtract luminance image from blurred star mask so that cores are excluded from mask, and on ly halos are represented in the mask = “Halo Mask”
Apply Halo Mask to main image, then run PixelMath to use Starless Image where halos otherwise would be
9. Photoshop
Use CloneStamp to remove halos from Starless Image, then subtract it from main image to remove remaining messy clumps in the background
Save as TIFF and move back into PI
9. Final
Final Histogram Transformation
Slight deconvolution to sharpen stars
ICC Profile Transform to sRGB
Resample to 67% of scale
Save as JPG
