LMC and NGC2070 at 480mm

[Greg Bock]

HI all,
North Group 80mm F6 refractor and Orion field flattner, Canon 600D, 15x5 minute subs, bias, flat and dark frames applied.

http://www.astrobin.com/124847/

Imaged this on 30 August from Leyburn but the colour of NGC2070 looks too green and blue to me. I have attempted to colour correct with MaximDL 6, and CCDStack 2 a couple of times, but not successful. eg. I tried splitting the RGB frames, then re-combining with reduced Blue %, but it didnt look correct.

Is there something about OSC images that I'm missing here? Any clue and helpful comments welcome.

[RickS]

Hi Greg,

Looks pretty good! I imaged the SMC with a mono camera and a lot of the nebulosity was OIII heavy and bluish so I don't think you're too far off. It would probably be improved by subtracting a bit of green (SCNR in PixInsight, HLVG in Photoshop.) You could get the reds to pop by adding Ha, of course...

Cheers,
Rick.

[multiweb]

That's very cool Greg. The hires has some serious image scale. Very refined and detailed. :thumbsup:
I don't think you'll get much red in the tarantula with a DSLR. Even with a CCD there's a big amount of greens and blues in it.

[MrB]

Hi Greg, even modded dslr's seem to show Tarantula as very blue-green, I suspect it has oodles of H-beta emission that overpowers the Ha. This is just a theory I've come up with to explain what I see, I've never been very successful in finding an official explanation.

[Greg Bock]

Thanks Rick, Marc and Simon..I'll have a fiddle, but I suspect you're right, I wont make much progress. I find a lot more red when it is imaged with the QHY8L..I must post that image too, but it was taken thru the MN61 at 900mm.

[Ross G]

Great looking photo Greg.

Sharp and detailed.

I think the colour is ok.

Ross.

[LightningNZ]

The ratio of H-a to H-b is pretty much fixed (1:2.85). Extinction from dust is apparently what causes the H-a to be lost ( http://en.wikipedia.org/wiki/Extinction_(astronomy) ), though I think there's a lot of OIII in this region too.

[Greg Bock]

Thx for tips guys..
Hmmm, had a fiddle with PS, adjusted it so less green around the Ha of NGC2070..better rendition?
see here for full res http://www.astrobin.com/full/124847/B/

[RickS]

Colours look better, Greg!

[LewisM]

In PS, use Adjustments -> Hue/Saturation and select blue and/or cyan and fiddle til it looks right. I know with my FLI 8300 OSC with an LP filter, I have to manipulate the blues a LOT.

I also find with CCDStack for OSC that it is IMPERATIVE to debayer PRIOR to registering and stacking, otherwise you get a "tartan" OSC grid effect, or very distorted colouration. Also use the Colour adjust to change the background - I always desaturate the background. It helps balance the blues a bit more too.

[multiweb]

As a rule you cannot register files that are not debayered or you'll destroy the bayer matrix.

[Greg Bock]

Thx Lewis and Marc
yes, second version has been treated exactly as you outlined Lewis, as well as de-saturating the background in CCDStack. And yes, Mark, exactly right, i found this out by mistake quite a while ago. :) which makes sense when you think about it.

I think the second one is much better, and also matches the same area taken with the QHY8L through the MN61.

[SimmoW]

Amazing image, I gotta try it one day soon

[andyc]

Actually great to read this - I've just got myself a 6" newtonian astrophoto rig, and one of my first targets was the tarantula (camera is an unmodded 60D). It came out just as blue-green as yours, and I worried about the reason . Even accepting the lower H-alpha sensitivity of the camera, it seemed a bit much, though I'd read about NGC 346 being more green than red , other nebulae have come out nicely red/pink in the 60D. A 1959 paper on the NGC 2070 spectrum notes a lot of OIII, but the spectrum in the paper didn't appear to cover H-alpha, so I couldn't make the comparison. But... it's reasonable that this nebula has a sizeable contribution of OIII.

I ought to add- lovely image too :)