Might want keep the background a little lighter. i think it has been over stretched.
Also look into how to make a star mask to protect your star data from over stretching and tweaks..
Thanks Rowland and John. This image was a disappointment from when the initial result came out in DSS. There are almost twice as many subs as in my previously posted image,84 in all, ranging from 20 to 100 secs. I'll have to examine them individually and see if there are any
really poor ones affecting the end result. I didn't keep a copy of the image in DSS, so I can't get back in and lessen the green a bit. I don't
know how to do it in PS. Incidentally, almost all M83s that turn up here
are blue, ranging from light to obviously over saturated, but almost all
of the top amateur and text book pro images of it show only a
relatively small amount of blue.
raymo
That's a good image Ray. Also some nights you can get away with less subs for the same result. Sky transparency and high level cloud may have something to do with it. On a moonless night, the only indication of high level cloud is when the stars wink in and out.
The uneven illumination is amp glow; I can remove it, but then the sky
becomes unnaturally black. It is much worse on the original result, so I have removed some of it. It's hard to know where to draw the line.
raymo
Yep! That's much better Ray. I think you clipped a lot of data in the first one. That lovely spiral glow is more evident in the second. Much more data than first impressions. There is a tendency to go for a black "space" background, but there is a lot of matter in between, on the scale that we observe - it's very colourful.
Iget it in virtually every shot once I've got a few shots under my belt in
any session. It is a specific shape, and always in a specific place. It starts
about a third of the way along the bottom edge of the image, and finishes
about two thirds of the way along. It heads up at an angle from each of
the two points to form a cone like shape which is about 1/4 of the image's width at the top of the cone. I don't get it in the first few images.
The sky has no visible gradient in the direction of M83. My house is in darkness, and I have a very long matt black tube fitted to my scope,
so I'm presuming that it's amp glow.
raymo
Ray. In fixing the background the fine detail is clipped. Despite the glow in the second image it is better in my view because the fine detail is visible.
Can you post the first sub with no apparent glow and a later sub with the glow. I'm interested in what is happening there.
Hi Rowland, I'll try and comply with your request, but it will not be right away, as my wife and I are going to Perth to stay with our daughter who
has presented us with a grandson. Last thing we expected, as she's 41.
Her other half is on 28days FIFO, so we're giving her a bit of help.
Also, the clear skies here are pretty much gone for the year; they're few
and far between once summer's gone. I don't have any examples with the
defect, as I throw out all the rubbish. My laptop is old, and slow, and a little cramped for space. Incidentally, flicking between the two images,
my old eyes can't see any difference in fine detail. I guess I would need to have them side by side to see it.
raymo
