M20 - The Trifid Nebula - an update

[cybereye]

My God, I can't believe I've managed to image and post something - it seems such a long time since I last did!

Anyway, here's my 2013 version of M20. I went with this neb so that I could compare both the RC8 and my skills compared to my two previous attempts using an 8" Newt. Imaging, as always, was done from my backyrd 12kms south of the Brisbane CBD using a QHY8L and guiding was done using an ST80 and PHD. The image consists of 33 x 5 minute subs stacked in DSS, processed in Startools and final cosmetics in GIMP.

Overall I'm happy except for the red fringe around some of the brighter, what should be yellow, stars. I'm not sure if this is an effect of my UHC-S filter or processing or both, so any advice would be greatly appreciated. I've also attached the 2012 and 2010 versions for comparison.

Mario

[marc4darkskies]

Not bad Mario, colours look good but I think you've hammered it too hard with noise reduction (?) - it looks far too smooth. Do some masking with your noise reduction to leave the bright, high signal neb alone.

Cheers, Marcus

[cybereye]

Thanks Marcus,

You're correct, I went in and did some additional noise reduction to what I normally do. I didn't think it affected my original image too much but I could be wrong - it's been known to happen!! I'm just happy to be out and imaging after a rather long hiatus...

Cheers,
Mario

[Ross G]

Hi Mario,

Good to see you imaging again.

Looks good.

I really like the colours.

Ross.

[cybereye]

Ross,

Thanks for the compliment!!

I've already started on a rework of this data taking into consideration Marcus' comments and his fantastic image. I've improved in several places, however I'm now just trying to work out a methodology to tame my blood-shot stars. I'm almost positive that the UHC-S filter I use to tame the LP is reducing the yellow in my images but I guess this is one of the things I have to deal with living in the middle of Brisbane!! Anyway, when I'm happy with the result I'll be posting it here - don't you worry about that! (Hey, I live in Queensland with the ghosts of Joh...)

However there are a lot of positives that I take from my latest night under the stars. Firslty, I am very happy with my new rig, the GSO RC8. Not only does it do a fantastic job at capturing those photons, but it holds collimation and focus well. I'm impressed at how sharp my images are compared to the newt, pre-processing. Also, at half the length and about 2/3 the weight of my old 8" newt, it's a lot less of a strain for my HEQ5 Pro mount.

Secondly, I'd made some slight changes in my PHD parameters and I no longer seem to have guiding issues. I'd lowered my calibration step from 2000 to 1000 and it seems to have worked a treat. MY alignment was also nearly spot-on with PHDLab giving me a mis-PA of 3.84 arcminutes, not quite 1/15 of a degree. Thirdly, if I could get this baby to a dark spot then I could ditch the light pollution filter and get some yellow back into my stars!

Well that's enough from me - as I mentioned before, stay tuned for a repro...:D

Cheers,
Mario

[strongmanmike]

Looking forward to it Muzza...with Marcus's Trifid at least you have something to try and copy, it's an essentially perfect image of the Trifid IMHO :)

Mike

[cybereye]

Thanks Mike - I know my image is not going to be as good as Marcus' considering his skill level, not to mention his location, gear, etc., etc., but I have got a rather large competitive streak which means I'll keep working at this until I get damn close to his! I'm currently driving my wife mad - "I thought you'd processed that picture already?" I heard her mutter as she walked past me at the 'puter last night.... It's the same competitive streak that made me think I could get past big Islander wingers of the opposition when I was playing Golden Oldies Rugby... and by God I did some of the time!!

Anyway back to the topic at hand. I've been getting some valuable advice from Ivo Jager regarding my missing yellow stars and so went back to look at my raw data. While I was carefully looking at the central region of the Trifid I noticed that the central stars seemed wonky. I thought that to add to my problems I had a mis-stack issue with DSS. "Great", I thought, "that's all I need!". However on more careful investigation it seems that rather than there being two stars, there are actually two bigguns and two small ones close together. As soon as I try to bring the white point up I lose the definition of these so that's something else I'll need to consider in my repro...

I've attached two images, firstly the central portion of a semi-processed piece of my data together with the Hubble equivalent. It's gratifying to get this sort of detail from the middle of a big city - it means that my gear is all working as it should and that collimation is pretty much spot on.

Right, back to processing....

Cheers,
Mario