SAS Astronomy Picture(s) of the Month [March, 2024]

IC443 - The Jellyfish Nebula in Gemini

IC 443, commonly known as the Jellyfish Nebula, is a supernova remnant located in the Gemini constellation It was discovered by Sir William Herschel in 1787 and gets its name from its intricate filaments that resemble the tentacles of a jellyfish. It marks the aftermath of a supernova explosion that occurred around 30,000 to 40,000 years ago, originating from a star estimated to be 5 to 10 times the mass of the Sun and about 5000 light years away. 


The image below is a 6h and 10min exposure using a C6 HyperStar and an IDAS NBZex dual narrow band filter on an ASI533C OSC camera.


David describes his workflow as follows:


Preprocessing with WBPP
Star removal with RC StarXterminator
Background gradient removal with GraXpert on starless image
PixelMath to add back stars
White balance SPCC
Tighten stars with RC BlurXterminator
Reduce noise with RC NoiseXterminator 
For “Hubble palette” experiments with the NB images I separated the channels with PI > Image > Extract > Split RGB channels and Extract Lightness
With the NB SII images, which were initially RGB, I simply convert to gray scale since all three channels got only SII light.
For the RGB images, which up to now are linear, I’ve been using Generalized Hyperbolic Stretch for stretching the image although sometimes I just use Histogram Transformation or HDRMultiscale Transform.
After stretching I usually make minor adjustments to the black point with HT and/or CurvesTransform then save the image as a 16 bit TIFF and transfer to PS
In PS I find  Filter > Camera Raw Filter to be very useful for tweaking the highlights and black point and playing with Effects > Clarity improves detail.

Photo by David Murray

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