hello members
can anybody help me with my photo from monday night
it seems to have an uneven brightness from the left side going darker to the right of the frame
very happy with my data actually
16 lights 180@800
16 darks (taken same night)
16 flats (taken next morn untouched camera)
thanks in advance
pat
Hi Pat. That is quite a gradient. Not sure flats taken the next day is necessarily responsible, though, I would take flats just after imaging, because they are quick to take and you can be extra sure of their suitability - focus/temperature.
I don't know how to remove gradients in PS or GIMP and prefer a dedicated program with a gradient removal tool. Perhaps the trial version of StarTools and see if the Wipe module will improve on things.
Hi Pat. That is quite a gradient. Not sure flats taken the next day is necessarily responsible, though, I would take flats just after imaging, because they are quick to take and you can be extra sure of their suitability - focus/temperature.
I don't know how to remove gradients in PS or GIMP and prefer a dedicated program with a gradient removal tool. Perhaps the trial version of StarTools and see if the Wipe module will improve on things.
that wouldnt be a bad idea though rowland but i dont have a light box so i can only do them the next day with the white t shirt trick!
pat
Hi Pat, was this gradient evident on the original subs? It looks very much like a light has intruded on the image somehow.
didnt notice any rod...... but i will take a closer look at them
my next pic of m83 i am about to post was done on the next night but it is perfect
pat
Hi Pat, was this gradient evident on the original subs? It looks very much like a light has intruded on the image somehow.
think you may be right now rod because my m104 in a similar part of the sky looks similar.......... bugger!!!!!
thanks mate i will avoid the same situation i future
pat
I've often found these gradient effects from the moon, light pollution etc. can be much worse if there is cloud about. Pat, are any of your subs affected by cloud? In which case reprocess without them, and/or use "median" rather than "average" stacking.
Pat. If you can post a tiff or png version of your original stacked, not post processed, image, it will be easy to run through StarTools and/or Pixinsight. Had a go with your original, but the small size and compressed format makes it difficult to manipulate the data. Intersted to see what they can do for it.
Pat. If you can post a tiff or png version of your original stacked, not post processed, image, it will be easy to run through StarTools and/or Pixinsight. Had a go with your original, but the small size and compressed format makes it difficult to manipulate the data. Intersted to see what they can do for it.
ha! got ya rowland..... i know now...... so just the raw stacked DSS image?
should have kept a copy of that
i am at work till about 9pm perth i will try and do that tonight and i would love for you to have a go at it mate
pat
Pat. If you can post a tiff or png version of your original stacked, not post processed, image, it will be easy to run through StarTools and/or Pixinsight. Had a go with your original, but the small size and compressed format makes it difficult to manipulate the data. Intersted to see what they can do for it.
rowland and anybody else this is the raw dss stack
thanks for the help
pat
Pat, it's still a jpeg though, which is a VERY lossy format. It's very hard to adequately stretch/fix etc a jpeg.
Need it as either a tiff of png. Of course, this site won't let you upload them as a good useable size, so IF you can, maybe upload the full size tiff or png to astrobin.com?
Or email me direct and I can host it. Straight out of DSS, saved as 16 bit embedded tiff. NO adjustments made.
(BTW, by default DSS saves an Autosave.tiff, which you may have turned off)
Pat, I had a go at adjusting your image using Pixinsight, just using the original jpg image you uploaded in your first post.
The gradient still remains to some extent (even with very heavy handed gradient removal), so my guess is that stray light from somewhere is affecting the lights, which was then not present when you did your twilight flats.
Did you have the viewfinder covered over during capture, as light can "leak" back into a DSLR via the rear viewfinder over long exposures. Other options could be your computer, lights on the mount, outside lights from your neighbours or the street etc etc. Perhaps even a dew problem?
thanks for your help lewis and richard...... i think it has become obvious to me now that it is a stray light problem......... i did do something different that night which was different to my other imaging nights thinking it would not make any difference as i have the long flexible dewshield
thanks guys i learned that one early and hopefully it will not ruin any more rare good viewing nights
pat
Hey Pat, I have used the techniques described in that youtube video Jon suggested and got great results. Its amazing how much that technique removes gradient from a shot. Would be worth a shot trying it on your data.
Hey Pat, I have used the techniques described in that youtube video Jon suggested and got great results. Its amazing how much that technique removes gradient from a shot. Would be worth a shot trying it on your data.
