IC 443 Jellyfish Nebula SNR (Robotic, NM)
IC 443, Sharpless 248
IC 443 is a supernova remnant in Gemini located between 2 bright stars - Eta and Mu geminorum. A pulsar - the remnant of the massive star that exploded has been detected towards the lower left hand part of the "jellyfish"
Its thought that the shock wave of the Type 2b (core collapse) supernova explosion has impacted on a relatively dense molecular cloud with excitation of elements such as sulphur - giving a reddish tinge to the jellyfish in this palette.
The shockwave has then penetrated through to a less dense cloud of hydrogen-rich (green) interstellar medium and then raced ahead rather like a jet of air escaping through the nozzle of a balloon.
I saw a nice image of this supernova remnant taken with just 3 x 6 minute subs each in Sulphur II (Red), Hydrogen alpha (green) and Oxygen III (blue) [the Hubble palette] so I thought I would try that with the same telescope. T20 - a 106mm refractor in New Mexico.
In practice however, 6 minute subs in narrowband are a bit underexposed and I found the subs to be quite noisy with a lot of column defects on the CCD chip. To get round this, I accumulated a lot more subs - between 25 - 36 x 6 mins in each channel and deliberately used the meridian flip to get both East and West subs so the column defects were evenly spread out. I had to make very extensive use of the Cosmetic Correction tool in PixInsight to get reasonable subs.
In retrospect, I think the image I saw was quite small and the noise wasnt obvious.
I worked on the luminance and chrominance images almost completely separately both in PixInsight and then as separate layers in Photoshop. I just brought them together at the end.
Lessons learnt - dont even think about short exposures in Narrowband - not enough light gets through!
Working with separate Lum and Chrom images is definitely worthwhile.
IC 443 Jellyfish Nebula SNR (Robotic, NM)
IC 443, Sharpless 248
IC 443 is a supernova remnant in Gemini located between 2 bright stars - Eta and Mu geminorum. A pulsar - the remnant of the massive star that exploded has been detected towards the lower left hand part of the "jellyfish"
Its thought that the shock wave of the Type 2b (core collapse) supernova explosion has impacted on a relatively dense molecular cloud with excitation of elements such as sulphur - giving a reddish tinge to the jellyfish in this palette.
The shockwave has then penetrated through to a less dense cloud of hydrogen-rich (green) interstellar medium and then raced ahead rather like a jet of air escaping through the nozzle of a balloon.
I saw a nice image of this supernova remnant taken with just 3 x 6 minute subs each in Sulphur II (Red), Hydrogen alpha (green) and Oxygen III (blue) [the Hubble palette] so I thought I would try that with the same telescope. T20 - a 106mm refractor in New Mexico.
In practice however, 6 minute subs in narrowband are a bit underexposed and I found the subs to be quite noisy with a lot of column defects on the CCD chip. To get round this, I accumulated a lot more subs - between 25 - 36 x 6 mins in each channel and deliberately used the meridian flip to get both East and West subs so the column defects were evenly spread out. I had to make very extensive use of the Cosmetic Correction tool in PixInsight to get reasonable subs.
In retrospect, I think the image I saw was quite small and the noise wasnt obvious.
I worked on the luminance and chrominance images almost completely separately both in PixInsight and then as separate layers in Photoshop. I just brought them together at the end.
Lessons learnt - dont even think about short exposures in Narrowband - not enough light gets through!
Working with separate Lum and Chrom images is definitely worthwhile.