M42 and M33

[jacko61]

Both captured last thursday night. Perfectly clear all night above South Lanarkshire but obviously affected by a near 90% full moon.  I took 3 hours of 4 minute subs on M33 but when I came to process the stack, I found I couldn't stretch the image to pull out all the detail without the image washing out completely. Pretty much the same story with  M42 - an hour of 30 second subs - again if I try to stretch the data fully the image gets washed out.  Obviously the solution would be not to image at full (or near enough) moon but I'm wondering if something like an l-enhance filter would have helped.  WO ZS73 and ASI533MC pro set up. 

Graeme

[Iem1]

Both look fantastic!

I imaged Orion at pretty much the same time, with the same scope and same integration time also with 30 second subs (but with a 600D) and got similar results. Even with flats there was gradient present with a harsh stretch, so the image couldn't quite reach full potential.

Edited January 24, 2022 by Iem1

[Clarkey]

Obviously at this time of year Orion is close to the full moon. I would try to target nearer the circumpolar regions as this is further away and will give a better image due to less atmosphere. This was taken around a full moon in rgb so it can be done.

[wuthton]

On 24/01/2022 at 13:50, Iem1 said:

Both look fantastic!

I imaged Orion at pretty much the same time, with the same scope and same integration time also with 30 second subs (but with a 600D) and got similar results. Even with flats there was gradient present with a harsh stretch, so the image couldn't quite reach full potential.

Dynamic Background Extraction (DBE) in Pixinsight is your friend for this. 

Edited January 25, 2022 by wuthton

[ollypenrice]

Watch your black point. You have discarded a huge amount of your data. If we look at your histogram we see the peak, containing all the nebulosity, crammed up against the left hand side. Much of that nebulosity would have been to the left of what is no longer there.

There should always be a small amount of flat line to the left of the histogram peak, like this:

There is a big temptation to move the black point slider (bottom left) to the right in order to get rid of gradients. Never, ever, do that. Fix gradients using a gradient tool like DBE in Pixinsight or Gradient Xterminator or equivalents in AstroArt, APP, etc etc. You need to preserve that little flat line to the left of the peak or you are 'black clipping' your image and when the data are gone, they're gone.

Olly

[jacko61]

19 hours ago, ollypenrice said:

Watch your black point. You have discarded a huge amount of your data. If we look at your histogram we see the peak, containing all the nebulosity, crammed up against the left hand side. Much of that nebulosity would have been to the left of what is no longer there.

There should always be a small amount of flat line to the left of the histogram peak, like this:

There is a big temptation to move the black point slider (bottom left) to the right in order to get rid of gradients. Never, ever, do that. Fix gradients using a gradient tool like DBE in Pixinsight or Gradient Xterminator or equivalents in AstroArt, APP, etc etc. You need to preserve that little flat line to the left of the peak or you are 'black clipping' your image and when the data are gone, they're gone.

Olly

Thanks for the advice Olly.  I've not been imaging that long so all my results using GIMP are through trial and error. I'll see if I can find a tutorial on gradients. Luckily I still have all the data.

Graeme