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Remove Light Pollution tool doesn't remove background properly?
Remove Light Pollution tool doesn't seem to remove background properly.
Light pollution gradients are removed but the background becomes quite red (for dual narrow band ALP-T filter).
If I check the check-box "neutralize-BG" in the right-hand panel, then the background is removed (but only for display).
PixInsight removes the red background easily with either ABE or DBE.
I thought images after LPC should be CBG as well...
Please share a screenshot of what is happening so we can better understand what is happening here and please show us where you placed the area select boxes. If you placed them correctly, the sky background should indeed be calibrated and color free. So if the sky background turns red, it most likely means you have not placed the area select boxes in correct places ?
Hi Mabula and thanks for answering!
This is for images taken with a dual-narrow-band ALP-T filter.
Images taken with a UVIR filter do not have this effect.
Here's some screenshots.
After Neutralize-BG check-box checked:
I did shoot the same targets and fov recently, too (but just dslr, not filter). So I didn't get the nebula as rich as you. (But surely nicer stars, lol)
But I have a mostly reddish background too. But only there (not in any other target before), so I do expect the whole area beeing covered by very faint red nebula (even in the dark background).
"bubble lpc after" shows the reddish glow in the background (but not where you set your boxes, these were used for background calibration too).
And it looks "best" of all 4 to me btw.
In "bubble lpc after neut" I think the auto neutralisation supresses this glow by neutralizing it. So if you want this, you have to do an extra background neutralization by setting boxes on the reddish parts.
But if I had this in my subs as "prominent" as you I surely would let it there to show it, rather than doing a pseudo "dark" background (even if you loose some punch due to the lower contrast, but you can get that afterwards)
(I do try to get it out more in mine atm... 😉 So I was surprised as i stumbled over your post this morning. Maybe we should trade some subs lol)
Yes, you could be right...
Hi @maxthebuilder and xyfus,
Thank you very much for sharing those screenshots. In fact it shows that the Remove Light Pollution tool is working very well instead of badly like you thought. The whole area is filled with H-alpha, that is why it is showing up because of proper background calibration done by the Remove Light Pollution tool.
If you use background neutralization with the checkbox below the histogram, it becomes surpressed because that is only a simple preview function that is using the histogram of the entire image 😉 The background neutralization will make the whole image neutral sort of speak and not only the background... so for such an image it only serves for an initial visual look of how it would look...
Now I am quite sure you can even improve here, when you work with the Remove Light Pollution tool you want to overstretch and oversaturate, then you will be able to better find the spot where there really is no H-alpha... You might see even more H-alpha in the data then now 😉
Of course you're right.
I was in fact fooled by PixInsight - its ABE or DBE would remove the Ha background...