Third of SMC

[Atmos]

I had planned a HaOIIILRGB 6 panel mosaic of the Small Magellanic Cloud but I had the bright idea of starting it too late in the season. Then with cloudy new moons and less then ideal seeing on the clear somewhat moonless nights, I only have 3/6 panels of RGB completed.

Transparency was reasonable (for a little while anyway) but the seeing left much to be desired. Each panel consists of 10x120s RGB and a synthetic luminance so three hours in total. I have bits and pieces of Ha and OIII, maybe even some lum but I think they're of various parts and some are in different orientations so I do need to sit down and collate what I've got at some point :)

Editing from start to finish took 15 minutes, nothing more than a stretch and LRGB Combine for saturation on all three and then stitched.

What I have since discovered (last night) is the focus offset and figured out some of the blue bloat. Although technically my RGB filters are par-focal with my L filter (they fall within the CFZ), they're on either side of it. The R being 3 microns out, G being 28 microns in and B being 23 microns out. As the telescope cools the focus moves in so by the time the B filter starts it's moved out of focus (no temperature stability at all in summer) while the G moves into focus.

I've dropped the resolution by 50% for upload, painful to get up otherwise :P

Higher Res (http://www.astrobin.com/283263/0/)

[Placidus]

A yummy shot. You've got the very best part of the SMC already. Like it a lot.

At the published resolution we can't see any issue with the blue. The two really big blue stars are just very bright. Adds interest.

Fred handles the focus problem by having faultless equipment - focused once when he bought it. Our focusser flops about wildly under gravity like an undercooked blancmange as we move across the sky, so we handle it by automatically refocusing before each frame.

Looking forward to seeing the finished result in a year or so if it ever cools down.

[RickS]

Shame you didn't get a chance to make more progress, Colin. Very cool project and hopefully you'll get a chance to finish the job, even if it's not this year.

IMO parfocal is a meaningless term suitable only for marketing brochures. Filters that are "parfocal" on a f/9 RC scope may not be on a f/5 refractor or on a f/3.8 newt. It also assumes that you buy into the belief that anywhere in the CFZ is good enough...

Cheers,
Rick.

[Atmos]

Thanks MnT. There is a blue ring around many of the stars, it'll probably be completely fixed simply by masking the stars when doing the LRGB Combine and saturation :P Too lazy for that at this stage, got to collate the random sections and angles I've got so far.
One panel to the top left would have been good, the last interesting bit on the "bottom" side of the SMC.

I know I need to refocus every 1°C of change. With these frames I did 20 mins red, green then blue. Focusing in Lum means that with an average of 1°C drop per hour by the time I've gotten to Blue it's already defocused without taking the focus offset into consideration.



I've got your SMC as a template ;) With some good seeing I have been hoping to be able to get it close to a resolution of 1.5-1.8" in Lum. Get in some high altitude Lum out somewhere :p:
I'll finish it later this year, late spring/early summer when it's in a favourable position again :)

I've had a lot of troubles trying to figure out the focus offsets, I've known that if I focus in L that my RGB are in focus (checked with bahtinov mask). Being a refractor I've not expected everything to be truly parfocal regardless of the filters accuracy :P

[Anth10]

Colin, although I'm not qualified to comment on the technicalities of image capture and process in this forum I can appreciate the care and effort it must take to produce such a compilation. 100% shown in this image. You should be pleased with it to this point and will certainly be satisfied upon completion.
Great work.:thumbsup:

[Stevec35]

An excellent result Colin and you certainly managed to get the best part of the SMC. I hope you manage to finish the rest at some stage.

Cheers

Steve

[Atmos]

Thanks Anthony :) I am happy with the way its turned out so far, just need to finish it :) Need some good high quality luminance to bring out the detail and depth :)



I've got some Ha and OIII for most of that big blank patch, going to make a mish mash of data at some point :P Definitely won't blend so well but it don't matter.