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Old 12-09-2020, 04:20 PM
jahnpahwa (JP)
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help with dumbell contrast

Hey legends,



I set up for the dumbell last night and ended up with almost no useable data, which was a shame. But, as i am new to this and just flat-out keen to see as much as possible, i still stacked the best 5 300s subs i had of Ha and Oiii to see what it'd look like.

The answer is not brilliant, but at least i see it
My question to you guys is, how can i keep the faint details of those shell-wave sort of things on the edge of the nebula, but also desaturate the central area, which is just white at the moment. The mapping here is HOO, and as i type this i wonder if i should do something like HHO, to stop the strong oxygen washing it out?
Or does this look like my subs are too long and i should go shorter to not flood the pixels in the centre? Each sub shows a fsirly white core in Oiii.
I dont really want to just mask the core and work it separately.

Any tips would be appreciated!



(Dont worry about the rubbish star color )
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Old 12-09-2020, 06:03 PM
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Sunfish (Ray)
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I am not a legend and I don’t really know much but I do a few hoo with a 1600 although not cool. I notice that you have higher 128 gain on many of your shots where I have dropped my gain back to 75 to avoid weird noise in fainter stacks. Don’t know if it helps because most of your shots look excellent anyway .Maybe just more Oiii required which I am finding needs to be double Ha.
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Old 12-09-2020, 06:11 PM
jahnpahwa (JP)
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Quote:
Originally Posted by Sunfish View Post
I am not a legend and I donít really know much but I do a few hoo with a 1600 although not cool. I notice that you have higher 128 gain on many of your shots where I have dropped my gain back to 75 to avoid weird noise in fainter stacks. Donít know if it helps because most of your shots look excellent anyway .Maybe just more Oiii required which I am finding needs to be double Ha.

Thanks Ray, i appreciate that advice do you know what offset you run at 75 gain?
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Old 12-09-2020, 10:13 PM
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Sunfish (Ray)
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I have tried 10 and I tried 20 and I am not sure I have any particular knowledge except that when you pull back on the gain due to the background sky you can keep the brightness down to default 10. There is a table here and discussion on cloudy nights also which lowers the offset . So I am trying 15 and dithering when I can .

https://www.cloudynights.com/topic/5...-maybe-qhy163/

Also tried squishing the RGB down to gain 1 to match the oiii Histogram but that is too far and all way over on the left. So back up maybe for RGB. Others here suggested I try the Craig Stark daytime histograms test For my sensor so that is how I ended up with 75.


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Thanks Ray, i appreciate that advice do you know what offset you run at 75 gain?

Last edited by Sunfish; 12-09-2020 at 10:24 PM.
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Old 21-09-2020, 08:28 AM
jahnpahwa (JP)
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wow, so much info on this camera! Thanks Ray.

With your suggestion in mind, I took a single 20min sub in Ha with gain at 0 the other night as I was packing up. Turned out as the sharpest pillars I've captured to date... at a 80mm and 450mm focal length, its attached below, cropped like crazy. I think 20mins is too long, even for 0 gain, but I think there is certainly plenty if life below 139.

As an indication of my laziness, re-doing my darks is actually holding me back from making the change across the board
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