burnt out stars when stretching

[planetdnb]

Hi Forum,

just a quick one. I took some subs of Plaides tonight (6 x 600s). I took 40 flats and 25 darks so I have some fairly nice clean data to play with.

I stack in Nebulosity and then I move over to Photoshop.

The issue I have is as I start to adjust the levels and curves to bring out the nebulosity (which looks stunning) the stars start to burn out and bloat.

Whats the best technique to avoid this happening? I'm assuming I am going to have to do something with layers/masking.

So far my attempts look a bit blatant. I duplicated the layer and then used the feathered eraser over the stars but it looks too obviouslt doctored.

Any help appreciated.

[ollypenrice]

In principle I think you are on the right lines. The rest is craftsmanship and 'touch.' (Not saying I have them though!)

Say you put the over exposed core on top. Now create a well feathered circular marquee over that and then try the eraser well below 100 percent opacity. Patence pays off. Only try to do one star at once. Probably accept a small improvement and then do it again, etc.

Or you could do it the really subtle way...

Compositing 2 Different Exposures via Layer Masks

While I used this for M42 I didn't try it on M45 so I can't say how it will work. I just did each star individually with a feathered marquee and variable opacity. I was not entirely happy with the result and aim to get back to it sometime. These were ten minute subs at F5.3. Nebulae and clusters. - ollypenrice's Photos

Olly

[planetdnb]

thanks for the feedback. i figured i might be on the right track but would need to be patient about it. I was just looking for a possibly lazy way.

I have used the technique you linked on Orion Nebula before. It worked very well.

Only issue I have with pliaedes is so many diffraction spikes it starts to look a bit doctored. I have had a good play with it and managed to do some magic with several different layers playing with opacity and brightness/contrast in each layer.

you can see it here:

M45 – The Pleiades, or Seven Sisters | ASTRO PHOTOS

[ollypenrice]

Oh, but that is very good indeed! Lovely dusty browns in the background, too.

One thing I would add is that as you pull the curve about you will alter the colour balance even if you only ever touch the combined RGB curve. So after setting the brightness of the adjustment layer, check out its colour balance before you flatten. I think you can see changes in CB around your reduced stars.

I wonder where that greenish oval comes from, by the way?

Olly

[planetdnb]

thanks for that.

the greenish oval really confused me too. In each sub it moves like a tiny little puff of smoke across each sub. Its an hours worth of data and its in every image moving slightly accross the distance of the green smudge. Very strange indeed!