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Contains:  M 1, Crab nebula, NGC 1952
Getting plate-solving status, please wait...
M1 - The Crab Nebula in Bicolor, 


            Josh Woodward
M1 - The Crab Nebula in Bicolor

M1 - The Crab Nebula in Bicolor

Technical card

Resolution: 3258x2112

Dates:Nov. 24, 2019Nov. 25, 2019

ZWO Ha 1.25": 42x600" (gain: 200.00) -15C bin 1x1
ZWO OIII 1.25": 16x600" (gain: 200.00) -15C bin 1x1

Integration: 9.7 hours

Darks: ~50

Flats: ~20

Flat darks: ~25

Avg. Moon age: 27.75 days

Avg. Moon phase: 3.86%

Bortle Dark-Sky Scale: 5.00

Temperature: 9.00 job: 3103397

RA center: 5h 34' 33"

DEC center: +22° 1' 8"

Pixel scale: 0.618 arcsec/pixel

Orientation: 277.549 degrees

Field radius: 0.333

Locations: backyard, Chico, CA, United States

Data source: Backyard


Modern understanding that the Crab Nebula was created by a supernova traces back to 1921, when Carl Otto Lampland announced he had seen changes in its structure.[5] This eventually led to the conclusion that the creation of the Crab Nebula corresponds to the bright SN 1054 supernova recorded by Chinese astronomers in AD 1054.[6] There is a 13th-century Japanese reference to this "guest star" in Meigetsuki.[7][8]

The event was long considered unrecorded in Islamic astronomy,[9] but in 1978 a reference was found in a 13th-century copy made by Ibn Abi Usaibia of a work by Ibn Butlan, a Nestorian Christian physician active in Baghdad at the time of the supernova.[10][11]
I was just able to get some OIII data before the holidays and poor Northern California winter weather kicked in.

Here are some Pixinsight processing details if you are interested:

Blink on both Ha and OIII to find really bad frames

Subframe Selector on both Ha and OIII

Weighted Batch Preprocessing with Nebula setting for Ha and OIII

Star Alignment to register Ha to OIII

Dynamic Crop with OIII as reference

DBE on Ha and OIII

Pixelmath to normalize Ha to OIII (instead of Linear Fit)

Pixelmath to make HOO image (red = ha, blue = OIII*0.7 + Ha*0.3, green = OIII*0.9 + Ha*0.1)

Create Lum channel

Background Neutralization

Photometric Color Calibration - I used Pixelmath to combine Ha with OIII in an attempt to get it as close to natural (RGB) as possible. PCC was able to take it the rest of the way.

Jon Rista SCNR+TGV+MMT noise mitigation process

Three part stretch - Initial HT stretch just until the nebula shows, small ArcSinh Stretch for colorful stars, Masked Stretch with no clipping

Lum Channel Processing

RGB Working Space - .33 on each channel

Deconvolution - tried several iterates on a preview until the deconstructions was not to strong settled at 0.0008 Global Dark and 125 iterations

Jon Rista TGV+MMT noise mitigation process

Two part stretch - small initial HT stretch and then Masked Stretch with no clipping

Used HT to try to match histograms of RGB with Lum.

LRGB combination with 0.4 saturation

ACDNR with strong mask to clip black tail

Created a range+star mask in Pixelmath to protect background for a Color Saturation

Color Saturation to taste

HDRMT to bring out some detail in the nebula

Star Mask and Morphological Transformation to reduce star size

Small Curves adjustment for contrast and saturation

Save to 16bit Tif

Photoshop CC

Raw Filter adjustments to taste

Save to jpg



Josh Woodward
License: None (All rights reserved)

Sky plot

Sky plot


M1 - The Crab Nebula in Bicolor, 


            Josh Woodward