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Old 22-05-2020, 02:32 AM
JA
.....

JA is offline
 
Join Date: Oct 2016
Location: Melbourne, Australia
Posts: 3,052
Quote:
Originally Posted by gregbradley View Post
Nice tight shot there JA but its very dark for the exposure time.
Thanks Greg. Yes I agree a little dark, but not sure I could do much better untracked since I was at 13 seconds @f/2 iso800 and I loose a stop or so with the Marumi Filter so it's as if it was around 6 seconds @f/2 iso800 in terms of light gather, which is very light on for subexposure given the other colourful Milkway images we see here (30 to 90 seconds) , I suppose depending on howmuch one wants to stretch and/or push the camera sensitivity .


Quote:
Originally Posted by gregbradley View Post
It does stretch and that will bring up a few gradients as well but those are correctable with a few tools - Pixinsight dynamic background extraction, Russell Croman's Gradient Xterminator or the Photoshop "apply image" trick.

There's more in this one.

Greg.
Yes good point, I did stretch somewhat and try stretching further, but as you rightly point out, the gradients needed to be contended with. I was using Sequator for the stacking and its light pollution removal option and I was not using flats and the resulting gradients / artifacts from stacking uncorrected vignetted images were significant. I then used lens correction in ACR in lieu of flats which improved the gradients, but they were still objectionable particularly with a brighter stretched image. I don't do Pixinsight, but I did try various Photoshop tricks. I may have to bite the bullet and use real flats to see if there is any improvement, but still given that I was about 50 metres from Nepean Highway with all those lovely High Pressure Sodium Lamps (SQM=18.8), I'm sort of OK with the result . Proper flats, tracking and much longer subs may work if the light pollution doesn't blow things out too much.

Best
JA

Last edited by JA; 22-05-2020 at 02:52 AM.
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