Another cracker of an image Peter. I think you could still stretch this a little more to fill the starfield and add more depth to this lovely image.
Again nice focus, guiding and star colours.
Thanks Doug. I'm finding the processing quite a challenge - so difficult to know when to stop. I'd like to see what you can do with it if you have time.
Hi Peter, I would love to have a go with the image but I need a file a bit bigger than this to work on. As this image stands the pixels square up very quickly with just a small adjustment. I will send you a PM with some logon details for my photo gallery so you can post an image up to about 40MB and I will have a look at it then.
Peter,
That's a great image. Crisp and clear.
I love the three little dark lines that run past the feather at the right bottom section of the cluster and often wonder what causes them.
Great work Peter. Layering sounds appealing, but is difficult work with clusters. The transition areas need to be smooth and seamless to be natural. A good alternative is digital development (DDP) as this will maintain the stellar profiles in the process. Don't stretch it too hard however, just enough to get the fainter regions showing, then finish it off with curves in PS or your tool of choice. Looking at the field illumination, it does appear as though you've applied flats. This will make it hard to extract more from what you've acquired. Obviously more data is always a good thing. Looking forward to seeing more.
Thanks Kev, Chris and Jase. I haven't tried DDP yet and have no idea what it does? Can you recommend any reading on the topic Jase? I did manufacture a flat in PS to reduce the vignetting using the R Scott Ireland methodology but now am in possession of a new light box so will be doing proper flats in the near future.
Peter, there are not many references online for the application of DDP. One of the best explanations I found was in the AIP4WIN book by Richard Berry and James Burnell. There are a few ways to apply DDP depending on what you want to achieve. Its easy to over do it and you'll find most tools set the mid point far too aggressive and requires manipulation to control the histogram curve. DDP is preferable over gamma or log stretches, though the latter works well. Like most tasks in a workflow there is risk you'll over do it - just keep an eye on the histogram after the DDP operation. MaximDL is notorious for black clipping so alter the background value by a few hundred counts to avoid this. You can always fix the black point in a tool that will give you greater control such as PS. If the DDP process is also doing sharpening, you may want to turn it off or at least keep a eye on the white point. Its not a replacement for levels and curves as many may believe. You'll still need to use the PS tools to finish off. If you're using DDP as a one stop operation, you'll find that you're pushing the data too hard, thats been my experience anyway. Its worth investigating further on some old data - experiment.
Cheers Jase. I realised I have DDP in Nebulosity and in my Astra Image PS plugin so will give them a try on the omega cen image. It looks like you need to apply it early in the processing routine according to the Nebulosity instructions.
Yes. Once you've got the master frame (combined subs), you're ready to apply DDP to it. There's different ways of using the tool. Luminance stretch is one, another could be to provide a colour boost on RGB data and later recombining as a layer in PS over the top of the DDP stretch lum. I wouldn't suggest you use it to stetch data for everything, but there are some images that can really benefit.
Your thoughts on layering the data (different exposures) can also be done using DDP. Simply alter the mid point/tone settings to control the aggressiveness. Each image could then saved and layered in PS. Though you'd probably get a similar result from a single application of DDP. You would need to try this out to validate.
