The Crab

I made the most of a short clear spell last Wednesday. This is the Crab Nebula- the first object in Messier’s catalogue. I captured it with my ASI 1600mm and 8 inch Newtonian – its first use since last September- with 30 minutes of RGB on the stars and then half an hour each on Ha and Oiii. Not really enough, but there was intermittent cloud throughout the evening and I rejected more of the narrowband subs than I kept.

I’m really fond of this object for several reasons: I love its place in history, with clear records in China in 1054 observing the actual supernova, it’s a good observing challenge and really jumps out with an Oiii filter, and it’s one of only 2 natural phenomena (the other being a neutron star collision) that we know of that produces Gold. I always get a bit whimsical and hold my wedding ring when observing M1, as a direct physical link to a similar ancient astronomical event.

Doesn’t look much like a crab to me though!

2 Responses

    1. Thanks Andy. I used Pixelmath for this. I made a narrowband only image which I put together HOO, with Blue dominating Green 2:1.

      I then made an RGB image, with 10 mins per channel and blended them with a formula.

      A couple of variables: TH=0.3, RGBF=0.9,NBF=0.2
      Then a formula: iif(RGB>TH,NB*NBF+RGB*RGBF,NB)
      Where the narrowband image is called NB and the RGB is RGB.

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