hi. when i take a series of images and stack them to gether i notice that they are very noisy and have red banding at the bottom of the image. is this to to with how the images are stacked to gether or mabye to do with the camera?
ok. i use a cannon 450D. exposure time can very from 30 sec to 10mins but this is still the outcome. i use deep sky stacker to stack them. i do use darks but the image seems less nosier if i dont use them. the iso used in thes images was 400. the images are taken in a darks site with little light around
Do you have ICNR turned off
Do you use a LP filter
Is the red appearing in the same spot on the final stacked images
also does it appear in the unstacked frames
do you use both darks and flats
is is more prevalent in the 10 minute exposures
Do you have ICNR turned off
Do you use a LP filter
Is the red appearing in the same spot on the final stacked images
also does it appear in the unstacked frames
do you use both darks and flats
is is more prevalent in the 10 minute exposures
Sorry just trying to narrow cover all options
thats cool.
no filter
no flats
is not seen in the unstacked pics. alsways in the same area in the final image.
If you take your first image and the temp is 24deg and when you take the last image the temp is 18deg then the last image will have half the dark current (noise) than the first. If you start taking darks then and by the time you finish taking the darks the temp is 12 deg then the last dark will have half the dark current than the first and only 1/4 the dark current the first light has. It is almost impossible to get accurate dark subtraction in this situation. Unfortunately this exact situation is not uncommon in SE Qld at this time of the year. You start taking images after twilight and finish taking darks 4 hours later.
I used to be a strong advocate for taking darks after lights. But I consistently get better result using ICNR now. If the temp is stable within a couple of deg then later darks can work well, otherwise I would strongly recommend using ICNR.
The biggest problem with ICNR is the loss of time collecting Lights. It takes two hours to collect an hours worth of lights. As with most things, its a trade off. If you have plenty of time then ICNR, if only a small window then darks later.
Mind you I'm not convinced that this is your problem, but trying this method may eliminate one factor that could be causing you issues.
i used icnr before but this made no difference, just took longer.
Quote:
Originally Posted by [1ponders]
If you take your first image and the temp is 24deg and when you take the last image the temp is 18deg then the last image will have half the dark current (noise) than the first. If you start taking darks then and by the time you finish taking the darks the temp is 12 deg then the last dark will have half the dark current than the first and only 1/4 the dark current the first light has. It is almost impossible to get accurate dark subtraction in this situation. Unfortunately this exact situation is not uncommon in SE Qld at this time of the year. You start taking images after twilight and finish taking darks 4 hours later.
I used to be a strong advocate for taking darks after lights. But I consistently get better result using ICNR now. If the temp is stable within a couple of deg then later darks can work well, otherwise I would strongly recommend using ICNR.
The biggest problem with ICNR is the loss of time collecting Lights. It takes two hours to collect an hours worth of lights. As with most things, its a trade off. If you have plenty of time then ICNR, if only a small window then darks later.
Mind you I'm not convinced that this is your problem, but trying this method may eliminate one factor that could be causing you issues.
Its not amp glow and it's not dark subtraction. To me that looks like its been way over stretched. We need to know what settings you are using in DSS and what post processing you are doing.
What format are you recording your images in RAW or jpeg? Are you stacking RAW. To me it looks like information is being deleted during the stacking process.
Its not amp glow and it's not dark subtraction. To me that looks like its been way over stretched. We need to know what settings you are using in DSS and what post processing you are doing.
setting i use are:
standard mode - align rgb channels
light - median
dark flat bias median
alignment - auto
i am use ing RAW