Messier 1 - The Crab Nebula with an SHO/RGB Blend
Date: November 11th, 2020
Cosgrove’s Cosmos Catalog ➤#0058
Messier 1 - The Crab Nebula. This image is a mix of SHO and RGB frames to provide stars that look a bit more normal. (click image for high resolution via Astrobin.com)
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About the Target
Messier 1 - The Crab Nebula. Also known as NGC 1952 and Taurus A.
Now, this is a pretty cool object! This is the remains of a star that went Supernova and was seen as a bright daytime star back in 1054 by Chinese Astronomers. It was discovered by English astronomer John Bevis in 1731. It was also independently discovered by Charles Messier in 1758 when he was trying to find the return of Halley's Comet. He thought he found it but what he actually found was this object. Charles then thought it might be a good idea to make a catalog of objects that could be confused with comets so that comet searchers would run into the same problem he had when looking for Halley's Comet. The resulting Catalog is the one we know and love as The Messier Catalog.
In 1840, it was observed by William Parsons, the 3rd Earl of Rosse, using his 36" reflecting telescope (a monster scope back then) and he produced a hand sketch that kind of looked like a Crab - thus its name. Unfortunate if you ask me - does anyone else in the world think this thing looks like a crab!
This nebula is 6500 light-years away and located in the constellation Taurus, in the Perseus Arm of the Milky Way. It has a diameter of 11 light-years and is expanding at the rate of 1500 kilometers per second! At its center lays the Crab Pulsar, which is a neutron star measuring about 17-19 miles in diameter - which just happens to be spinning 30.2 times per second! This spinning neutron star is emitting pulses of radiation from gamma rays to radio waves.
The Annotated Image
The annotated image was created using the ImageSolver and AnnotateImage scripts in Pixinsight.
About the Project
This image is the result of about 6 hours of integration using both narrowband and broadband RGB filters. Narrowband filters greatly restrict the light that reaches the sensor so you typically need longer exposure for them. In this project, I used 300-second subs (5 minutes each). On the other hand, I used shorter exposure for the RGB filters of 60 seconds. This allowed getting good RGB star images that were not over saturated. The colors are the result of a narrowband/RGB blend using the SHO Hubble Palette which provides false colors. This blend is also responsible for making the stars appear more natural than you typically see in a narrowband image.
This shot was taken during the incredible weather we have had for the past two days - a rare thing in November.
The filaments seen in the nebula are brought into significant relief with the use of narrowband filters. With the normal RGB they are much more difficult to see. These filaments are the remains of the original star's atmosphere that was blasted away when it went supernova. They consist largely of ionized helium and hydrogen, as well as carbon, oxygen, nitrogen, iron, neon, and sulfur.
I was really surprised at the resulting look of the image - I had a lot of fun working on this project and I hope you enjoy it as well!
The Location in the Sky
FreeStarChart,com Constellation map showing the location of M1 indicated by a yellow arrow.
Capture Details
Light Frames
20 x 300 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II Ha Filter
20 x 300 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II O3 Filter
20 x 300 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II S2 Filter
10 x 60 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II R Filter
10 x 60 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II G Filter
10 x 60 seconds, bin 1x1 @ -15C, unity gain, ZWO Gen II G Filter
Total of 6 hours
Cal Frames
45 Bias exposures
25 Dark exposures
45 Ha Flats
45 O3 Flats
45 S2 Flats
45 R flats
45 B flats
45 B flats
Capture Hardware
Scope: Astrophysics 130mm Starfire F/8.35 APO refractor
Guide Scope: Televue 76mm Doublet
Camera: ZWO ASI1600mm-pro with ZWO Filter wheel with ZWO filter set
Guide Camera: ZWO ASI290Mini
Focus Motor: Pegasus Astro Focus Cube 2
Camera Rotator: Pegasus Astro Falcon
Mount: Ioptron CEM60
Polar Alignment: Polemaster camera
Software
Capture Software: PHD2 Guider, Sequence Generator Pro controller
Image Processing: Pixinsight, Photoshop - assisted by Coffee, extensive processing indecision and second-guessing, editor regret and much swearing…..
Standardizing the base
Finally, the Tri-Pier and the its extension column arrived. This allowed me to standardize the base of the two telescope platforms. There are several reasons that made this useful. First - everything is the same when you are handling things in the dark. And secondly, I was in the process of revolutionizing how I setup at night…..