IC443 (Jellyfish Nebula) - Ha and HaRGB

[strutsinaction]

Hi

I revisited IC443 (Jellyfish Nebula) recently to capture some R, G and B subs to add to the Ha subs I captured last year. This is the first time I've attempted HaRGB (R channel enhanced with Ha). Overall, I'm quite pleased with the result although I still prefer the original monochrome Ha rendition which shows far more detail.

The FOV for the RGB capture was not quite as large as it should have been due to human error. I inadvertently unscrewed rather than rotated the Tak camera rotator from the OTA during framing. Doh! I only realised something was amiss when capturing the B subframes - PHD2 guide error and severe star trailing on 1 subframe. It was only later when I was packing up that I noticed that the camera rotator was loose! The end result was that the registered RGB frames required more aggressive cropping to get rid of the boundary artefacts. Lesson learnt, probably!

This is also the first time I used the MURE DeNoise script in PixInsight which has impressed me a lot. I'll be using this from now on for NR.

Details:
Avalon Linear/Tak FSQ85/QSI690
Ha 20x600s 1x1, RGB 20x200s 2x2
Captured with SGPro and processed with PixInsight.

Regards
John
 

[swag72]

I really like the mono rendition. I think that the halo is quite severe in the red version and also I feel that a lot of the lovely detail has been lost in the red.... Mono for me for sure, this is a stonking image

[Starlight 1]

+1 on HA very nice.

[strutsinaction]

2 hours ago, swag72 said:

I really like the mono rendition. I think that the halo is quite severe in the red version and also I feel that a lot of the lovely detail has been lost in the red.... Mono for me for sure, this is a stonking image

Thanks, Sara! Yes, looking at my R, G and B masters it's clear that the extended halo is coming from my B subs. I'm not sure is this is a characteristic of the Baader blue filter, or perhaps my dew heater wasn't turned up high enough? I captured the blue subs last of all and by that time the temperature had dropped to around -2C.

[strutsinaction]

21 minutes ago, Starlight 1 said:

+1 on HA very nice.

Thanks! Yes, the Ha does bring out lots of interesting detail.

[Barry-Wilson]

The Ha version does it for me - fabulous. Top drawer!

The HaRGB has a tinge of green in the background to my eye.  If using the HaRGB script in PI, I have blended the RHa and HaR imgaes sometimes to get a more pleasing result (admittedly, it is very subjective).  Like you, I find that a good deal of the Ha finer structural detail can be lost when combining HaRGB.  I've tried numerous times to master the PI Star Halo Reducer script but not been able to produce an effective result.  David Ault has an interesting (and PixelMath challenging) technique here if you haven't seen this, http://trappedphotons.com/blog/?p=616  I've never tried this though: good luck!

[strutsinaction]

Thanks Barry!

I followed Kayron Mercieca's excellent tutorial on Ha + RGB combination, a technique based on one proposed by Vicent Peris from the PixInsight team:

http://www.lightvortexastronomy.com/tutorial-combining-lrgb-with-narrowband.html

I also tried the NBRGBCombination script which produced very similar results.

Thanks for the 'Star Halo Reducer' hint. I'll take a look. I did use the MorphologicalTransformation process to reduce the size of the stars in the HaRGB image but it stopped short of shrinking Propus and its halo.

Regards
John

[laudropb]

Very nice images. The mono version gives more fine detail.

[ollypenrice]

Super. It's true that it's impossible to keep the fine detail of NB in a BB image, alas. If only...

This object has a splendid outer shell in OIII, rather like that around the Crescent.

Olly

[strutsinaction]

Thanks Laudropb and Olly (and the OIII hint)!

Regards
John

[Martin-Devon]

Yep, the H-alpha version you've done looks superb. The OIII data is weak for the jellyfish, so to have any chance to pull out that outer shell try to get data (and lots of it) on a moonless clear night - which are like hen's teeth where I live!

Martin

[ultranova]

Very nice , both of them, but the HA pips it for me as well

well done

Paul

[strutsinaction]

Thanks Martin and Paul. I was hoping to start capturing some OIII tonight. All set up and the clouds have just rolled in even though the forecast was clear skies. Grrrr.

[gorann]

Stunning, particularly the Ha image! Congratulations!

Being a marine biologist, I have difficulties identifying the jellyfish. Looks much more like a furry monkey head to me. So I think there must be at least  two Monkey Head nebulas around.

[strutsinaction]

Cheers, Goran! Furry monkey head? Yes, I see what you mean 

Regards
John

[toxic]

very nice jelly fish John