NGC 3532 is a large, rich open cluster at the prow of Argo. We were strongly motivated by Andy Campbell's recent much wider field shot, which includes this area, using combined narrowband and RGB, and showing much interesting nebulosity.
Here we have only the Eastern half of the cluster NGC 3532, a small part of Andy's field, with 6 minutes each RGB (2 min subs) and 3 hrs H-alpha in 1 hr subs as luminance.
We tried to capture both the nebulosity and the richly varying colours of the stars.
Colours:
We see a very striking range of colours, with many blue-white stars typical of an open cluster, plus a handful of bright orange stars. The background shows many tiny orange-red stars.
An image and write-up by ESO describes the cluster as containing about 400 members, ranging from lots of obvious brilliant blue-white young stars to a handful of orange giants at the end of their lives, and very many much smaller cooler red dwarfs. That fits with what we see.
The ESO shot is perhaps a little extreme in its saturation. We've tried to be a little more sedate.
The PPM catalogue shows the blue-white stars in our image are spectral class around B5 (scorching) to A2 (merely incandescent), while the handful of bright orange ones (presumably the red giants) are a merely warm K2 or thereabouts.
Nebulosity:
The parent gas that formed the cluster must have largely dissipated. Lots of very soft, gentle H-alpha throughout the field, but perhaps unrelated. No hard edges, no shock fronts, anywhere. These must have all dissipated by now.
This is the first time we've tried using H-alpha as a luminance channel, in order to show the nebulosity but at the same time show star colours. In this particular case we seem to have gotten away with it.
Why only half the cluster? We did do a mosaic of the whole thing, and have RGB for the whole thing, but the serial port controlling the cameras decided to die during the H-alpha for the western part. We'll have another go later.
The image looks terrible displayed in my browser (Chrome, wide gamut laptop screen) but downloaded and displayed with a colour managed application it looks great! @#$%ing colour management
A very attractive image, M&T It's not easy to make an open cluster look interesting.
Mighty pretty colours there guys, look forward to seeing the finished mosaic!
Delighted to have returned the favour and found an inspiring target for you to work on, reckon you've provided me with heaps
The image looks terrible displayed in my browser (Chrome, wide gamut laptop screen) but downloaded and displayed with a colour managed application it looks great! @#$%ing colour management
A very attractive image, M&T It's not easy to make an open cluster look interesting.
Our hearts sank when we read the first sentence, Rick. Perhaps we should scrap the thumbnail. Glad the downloaded real thing looked better.
Quote:
Originally Posted by strongmanmike
Excellent, perhaps some more saturation in the gas might look pretty but have to say, the gas.... really looks like gas!
Agree with Rick, it is hard, a nice scene that
Mike
Thanks, Mike. We'll think hard about how to bring out colour in the gas.
Quote:
Originally Posted by Andy01
Mighty pretty colours there guys, look forward to seeing the finished mosaic!
Delighted to have returned the favour and found an inspiring target for you to work on, reckon you've provided me with heaps
Cheers, Andy!
Quote:
Originally Posted by Atmos
Very nice MnT!
I do agree with the other Mike, a little more saturation on the gas would give it a bit more punch
Hi, Colin. Will see what can be done. At the moment, it has no colour whatsoever because when applying L to RGB we intentionally bias very faint stuff to be less saturated (so that background grit doesn't produce colour noise) and the gas is extremely faint, so it gets extremely desaturated. Will need some thought.
Quote:
Originally Posted by el_draco
Very pretty! Colours are excellent.
Thanks, Rom.
Having a crack tonight at getting the H-alpha for the other half of the mosaic, but there's clouds scudding about and probably nothing will come of it.
It is not often that pictures of open clusters impress me, but this one does. You've got a nice range of colours and it's quite a feat to have included the faint nebulosity as well.
However, the stars look a bit strange to me. A hard-edged core with a fuzzy halo looks artificial. Also, there are some dark halos around the brighter stars in the nebulosity--deringing artefacts perhaps?
Geoff
A great choice of object and framing. Very interesting.
My first thought though was that the colours seem off. The blue seems to have too much cyan in it and overall perhaps the image has too much green.
Colour is a hard one to comment on as monitors vary etc but your other images looked fine on this monitor.
Sorry for the late reply, chaps. We've been plagued by a never-ending cascade of hardware and software failures - did something bad in a previous life perhaps - and have become very discouraged. No end in sight.
Quote:
Originally Posted by topheart
Lovely colours!!
Beautiful!
Thanks,
Tim
Thanks for the much needed encouragement Tim.
Quote:
Originally Posted by Geoff45
It is not often that pictures of open clusters impress me, but this one does. You've got a nice range of colours and it's quite a feat to have included the faint nebulosity as well.
However, the stars look a bit strange to me. A hard-edged core with a fuzzy halo looks artificial. Also, there are some dark halos around the brighter stars in the nebulosity--deringing artefacts perhaps?
Geoff
Thanks for the feedback, Geoff. When I recover sufficiently from my current miseries, I'll have a look at the star profiles. Probably something to do with how I combined the Ha and RGB.
Quote:
Originally Posted by gregbradley
A great choice of object and framing. Very interesting.
My first thought though was that the colours seem off. The blue seems to have too much cyan in it and overall perhaps the image has too much green.
Colour is a hard one to comment on as monitors vary etc but your other images looked fine on this monitor.
I could be way off but that's my impression.
Greg.
Again thanks Greg. Must have another look at it, perhaps after getting some OIII and SII, should we ever get things working again.
The gear is working fine for about three hours at the moment, and then dying with an unhandled exception from the Apogee camera DLL. That's kinda unfriendly of them. Very hard to see how to proceed. Feeling seriously discouraged at present, and concentrating on building our new stockyard. At least that's looking rather fine. No colour or profile issues, and it doesn't crash at 1 am.
Interesting view. Colours look ok on my screen, maybe the Ha gas is a little under saturated, perhaps it should be more magenta, however I like the star colours and background looks good.
Interesting view. Colours look ok on my screen, maybe the Ha gas is a little under saturated, perhaps it should be more magenta, however I like the star colours and background looks good.
Hi, Paul,
Hi, everyone,
Here is the completed mosaic (two panels) showing the entire cluster.
H-alpha as luminance (5 x 1hr subs), RGB 26 minutes per channel in 2 minute subs. Aspen CG16M on 20" PlaneWave.
There is nothing especially magical about this image, but due to a never-ending list of technical issues and charming weather, it took weeks to aquire. The list of character-building disasters finally stood at:
- Lightning strike nearby, set fire to neighbour's paddock
- One dead computer
- New computer mysteriously needed new camera drivers.
- Two dead power supplies.
- One damaged microcontroller board. Built a new one from scratch.
- One dead fan. Fixed for $14 and $30 postage.
- One dodgy USB hub. Fixed in seconds for $103 from Office Works.
The last one was a real because the Apogee camera DLL would crash with an unhandled exception after 3 hours or more, rarely the same way twice, and we were thinking dying cameras, wiring harnesses, hideous latent errors in our code, etc etc. None of this was true. Pulling any one of the four USB cables to the cameras and filter wheel, or pulling the power supply to any one of them replicated the fault. Replacing the USB hub fixed it.
We've taken into account the accumulated comments - tad too green, stars a tad too aqua, nebulosity a tad undersaturated. We think this looks better.
The stars are interesting in that there really are three populations: bright blue-white typical cluster stars, a handful of very conspicuous orange coloured giants, and an ocean of distant milky way warm orange sand.
The nebulosity is only interesting in its complete lack of interest, which is hard to achieve.
Anyways, Placidus Observatory is now up and running again after more than a month of heartache and hatred, and has worked fine 3 nights in a row, working on the Hamburger and Master Yoda.
This imaging can be a frustrating game but you certainly copped a bad hand this time, M&T! Love the colour in the completed mosaic
Cheers,
Rick.
Quote:
Originally Posted by Andy01
Only on my iPhone but must say thems be mahty purty stars alright!
Nice work, persistence pays off again!
Thanks muchly, Rick and Andy. Pleased to report that the gear all worked for a fourth night in a row. Time to pour a little thank-you wine under the nonexistent pomegranate tree.
It's not easy to make an open cluster look interesting.
