Ain't no dragons fightin' here!

andyc (Andy) · #1 02-06-2015, 09:28 AM

My attempt at NGC6188 this last New Moon.

About 4 hours of images (25 x 5 minutes and 122 x 1 minute) with the EOS 60D on my Newtonian. Not the best conditions, with encroaching dew, some experimentation by me and some tube flexure of some sort, finished off by some ropey stacking, especially in the top left. - but it's an OK image, especially when viewed at smaller sizes!

I've really struggled with the colour of this area, after prattling on about colour last week

. This seems to be a real blend of emission and reflection, and it felt quite hard to get anything much other than magenta appearing strongly without unbalancing the view - more blue in the area than usual? Marty's excellent shot was a guide too (and a standard to wish for). I *think* there's a decent bit of blue reflection around the bright star and the patch towards the top, but feel free to tell me the colour balance is all wrong, I'd deserve it

That said, a larger view is here.

I wanted to run the experiment comparing lots of short exposures with fewer long exposures (hence the mix of 1- and 5-minute shots), but I think the dew leads to an unfair comparison so I'll not likely process up the two sets separately.

Robert9 (Robert) · #2 02-06-2015, 09:45 AM

Great effort Andy. Dew is always a killer. Is there a birthday near that you could put a dew-strap on the list?

I'd like to discuss further, partic. colour but have to go. Will get back.
Robert

Camelopardalis (Dunk) · #3 03-06-2015, 09:45 AM

A triumph against adversity? Got to be happy with that Andy! Lots of nebulosity there.

Has a slight yellow cast at least on my screen, but believe me I know how tricky colour balancing is since having my camera modded

Robert9 (Robert) · #4 03-06-2015, 11:23 AM

Quote:

Originally Posted by Robert9

I'd like to discuss further, partic. colour but have to go. Will get back.
Robert

I had a bit of a go at your image with PS and found that there wasn't much blue in it. So, that's the way it must be. Good work!
Just as an aside, apart from variations in camera response, our computer monitors also vary a lot. I have mine calibrated, but I don't know how long that lasts. Maybe I'll check it again ...... sometime.

Robert

cometcatcher (Kevin) · #5 03-06-2015, 12:33 PM

I love it. Lots of things to see in the image.

andyc (Andy) · #6 03-06-2015, 08:54 PM

Quote:

Originally Posted by Robert9

Great effort Andy. Dew is always a killer. Is there a birthday near that you could put a dew-strap on the list?

I'd like to discuss further, partic. colour but have to go. Will get back.
Robert

Thanks Robert. Dew straps are attached! So no issue with secondary - I think there was a little dust on the primary that nucleated a little moisture. Have cleaned the primary, and am working on insulating the outside of the tube round the primary (strap and bit of camping mat).

Quote:

Originally Posted by Camelopardalis

A triumph against adversity? Got to be happy with that Andy! Lots of nebulosity there.

Has a slight yellow cast at least on my screen, but believe me I know how tricky colour balancing is since having my camera modded

Thanks Dunk! Maybe just a little, yellow especially in the stars (compared to some other images) - perhaps I'll have a look at it again.

Quote:

Originally Posted by Robert9

I had a bit of a go at your image with PS and found that there wasn't much blue in it. So, that's the way it must be. Good work!
Just as an aside, apart from variations in camera response, our computer monitors also vary a lot. I have mine calibrated, but I don't know how long that lasts. Maybe I'll check it again ...... sometime.

Robert

Yes, looking at others' images it seems there's a little bit of blue reflection, but the reddish emission dominates. But thought there's not much blue in the one I posted, I did make one that was much bluer!

Quote:

Originally Posted by cometcatcher

I love it. Lots of things to see in the image.

Thanks Kevin!

bugeater (Marty) · #7 03-06-2015, 09:55 PM

Looks pretty good to me!

Maybe ditch the dewy shots if you think they're a problem. There is a subframe selector script in pixinsight you could perhaps run to select the best of your subs. You've definitely got a lot to chose from.

I too had a lot of difficulty getting much colour out of the region, but it's one I'd like to go back to and explore a bit further.

Did you take these subs from a light polluted area?

andyc (Andy) · #8 04-06-2015, 12:06 PM

Hi Marty, yes, there is moderate light pollution - as a guide I can pick out the LMC, but not always the SMC. So it's better than it might be, but a long way from properly dark here just within the edge of Sydney.

I've been playing with the subframe selector - it's a great tool. I did my exposures as 13x 5min, 122 x 1min, 12 x 5min, and the selector shows nicely that the sky background darkens as the frames get higher in the sky (very roughly 30deg to overhead over the time). But also the bloating gradually increased. Using just the first hour of shots didn't really help, because they're noisier - so realistically it's one for me to return to in better conditions, and maybe a darker sky. Much as I could try, say the first 2 hours of data (1 & 5mins), they're lower altitude too, and it's probably not really worth the effort. I might change my mind if we get 3 months of cloud sometime

.

bugeater (Marty) · #9 04-06-2015, 07:53 PM

Quote:

Originally Posted by andyc

Hi Marty, yes, there is moderate light pollution - as a guide I can pick out the LMC, but not always the SMC. So it's better than it might be, but a long way from properly dark here just within the edge of Sydney.

I don't think I'd have a chance of spotting either cloud here. Wish I could have my own dark sky site - maybe I could buy a farm once I've paid off the mortgage.

I found TGVdenoise worked quite well to smooth out the background noise. Works really, really well if you don't have many subs. You've just got to tweak the settings so you don't overdo it.