gorann Posted April 23, 2017 Author Share Posted April 23, 2017 11 hours ago, wimvb said: First version is in an album I created here a few days ago. I'm struggling with Ha integration. Normally I don't do HaRGB, so I'm learning. Will come in handy once I get a new camera, hopefully the ASI1600 mono. I think that looks very promising Wim (although your images are in such a small scale I cannot do my usual pixel peeping) Link to comment Share on other sites More sharing options...
wimvb Posted April 23, 2017 Share Posted April 23, 2017 There should be a button near the top (right) that lets you choose image size. Largest is abt 1600 px, which is the actual size ( slightly cropped after stacking). I didn't downsample the image. Link to comment Share on other sites More sharing options...
gorann Posted April 23, 2017 Author Share Posted April 23, 2017 2 hours ago, wimvb said: There should be a button near the top (right) that lets you choose image size. Largest is abt 1600 px, which is the actual size ( slightly cropped after stacking). I didn't downsample the image. Got it (stupid me)! You have got a fantastic amount of detail in that image compared to what I have seen of the Large Dumbbell before! How much data is it? If you are not pleased with it I assume you think about the colours, but I find those quite ok but they could probably be tweaked towards more saturated bluish and red. I think Olly says that there is no green in space. I just tried to do this quick and dirty. When I downloaded your image I realized too late that it was only 8 bit and about 1200 x 1200 pixels, so my attempts to change the colours (just altering the curves for the different channels) and sharpen it a bit are obviously not optimal. I am sure you can do it much better on your original data. Sorry for hijacking my own thread and your image Link to comment Share on other sites More sharing options...
wimvb Posted April 23, 2017 Share Posted April 23, 2017 Yes, that looks very different. If there isn't any green in space, then why is the LT green channel so much stronger than the blue. Is it only due to the camera and filters? Link to comment Share on other sites More sharing options...
gorann Posted April 23, 2017 Author Share Posted April 23, 2017 Well, the "green channel" is Bessel V that is not exactly the same as a green filter in the RGB filters we normally use. Found these curves for the filters and as you see the Bessell V is rather broad, sampling a lot of OIII, about as much as Bessell B, and also quite a bit of red, so it is broader than a normal green channel. I have been fighting a to suppress the green in my LT processing. Link to comment Share on other sites More sharing options...
wimvb Posted April 23, 2017 Share Posted April 23, 2017 This is from the LT site: If a nebula emits at Hb (486 nm) and/or OIII (490 - 500 nm), the green filter will have the higher transmission (throughput), and will give the brighter image. Which gives me this result on the little dumbbell Link to comment Share on other sites More sharing options...
gorann Posted April 23, 2017 Author Share Posted April 23, 2017 2 minutes ago, wimvb said: This is from the LT site: If a nebula emits at Hb (486 nm) and/or OIII (490 - 500 nm), the green filter will have the higher transmission (throughput), and will give the brighter image. Which gives me this result on the little dumbbell Yes,Wim, that curve shows it clearly: we need to suppress the green in the LT data to make it more into a true RGB image. Obviously, their filters are made for standardized physical measurements and not for colour imaging. We just have to make the best out of it. Nice image and you managed to save colour in the core (but I would put more effort into masking the stars when stretching.) Link to comment Share on other sites More sharing options...
wimvb Posted April 23, 2017 Share Posted April 23, 2017 I totally agree on the star issue. This image isn't supposed to be finished. Rather, I used it to test different techniques for keeping colour in the core, and I didn't bother about the stars. But I did shrink them a little (!) at the very end of processing. As for the neb colour; I tried a version with B and G switched (RBG if you will). It has the blue nebula (obviously) but green stars. I don't think the V filter data should be suppressed. If the light is from oxygen, it falls between Blue and Green. Maybe the V should be mixed in with the B? Link to comment Share on other sites More sharing options...
gorann Posted April 23, 2017 Author Share Posted April 23, 2017 1 minute ago, wimvb said: I totally agree on the star issue. This image isn't supposed to be finished. Rather, I used it to test different techniques for keeping colour in the core, and I didn't bother about the stars. But I did shrink them a little (!) at the very end of processing. As for the neb colour; I tried a version with B and G switched (RBG if you will). It has the blue nebula (obviously) but green stars. I don't think we should suppress the V filter data. If the light is from oxygen, it falls between Blue and Green. Maybe the V should be mixed in with the B? Well, what we try to do in RGB images is to imitate what our eyes perceives as red, green and blue. At least I aim at that. No one could ever sell a DSLR camera if it had a Bayer mask with Bessell filters. So I think we have a good excuse to tweak the data, or we could not call it RGB since these are not RGB filters. Link to comment Share on other sites More sharing options...
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