I'm very new at this processing stuff, and got very excited when i stacked 9 images and actually saw a difference in the final image.
The images i used in this procedure were colour, but i had previously changed them to Greyscale, and Auto Contrast in Photo Shop, was this a mistake and should i have first Dark Subtracted, and Callibrated, then alinged and stack, and then final processed, in that order.
Could someone please put the steps in the right order.
And also suggest what is the best save format to use from the Raw Images, captured before i start to do anything.
If i get the order in which to do things right, i'll be able to play and get it right eventually.
Thanks Heaps Leon
THought i had better add the image i took with my new sundial as someone mentioned, it is of the Crux Region,
You can dark subtract with Registax, but I've not tried it before.
The order of processing should be something along these lines. Convert Raws to 16 bit Tiffs (including darks), combine your darks to created a master dark. You can use registax for this but I've never been very happy about how well it makes a master dark. Then, dark subtraction, flat subtraction (if using flats), aligned, optimized, stacked and waveletted in Registax. Save as tiffs again if your post processing program handles tiffs. Then reopen into your post processing package and complete your curves and levels adjustments.
Alternatively download IRIS (free) and download Jim Solomons Cookbook and give IRIS a go. Pretty steep learning curve but if you follow the Cookbook it will give you a good starting point.
That will be agreat help, i can do most of that stuff, but it was diong it in the correct order that had me a bit puzzled.
They say practice makes perfect, so i'll just plug away, and learn as i go.
Hi All
Well i had another go at this aling and stack business, and things are improving a little, the blue tinge is caused by the light pollution filter, i think, seems to happen with all the DSLR shots.
Anyway it's getting better, 9 frames aligned and stacked, still having some trouble with the dark subtraction though,
Nice image Leon. My first few were a little rougher than that! Registax is a pretty flexible program - there are lots of options, so it does seem a bit daunting first up.
Please let us know how you go with Dark Frame subtraction. I am most interested. I have given up on trying deep sky stuff for the moment because I have a problem where the "black" sky ends up psychadelic colours after dark frame subtraction. I haven't sorted it out yet... I've just stepped back for a while to get some planetary imaging under my belt so it doesn,t get too frustrating... Still plenty of lessons fo me to learn!
Quote:
Originally Posted by [1ponders]
Hi Leon.
You can dark subtract with Registax, but I've not tried it before.
The order of processing should be something along these lines. Convert Raws to 16 bit Tiffs (including darks), combine your darks to created a master dark. You can use registax for this but I've never been very happy about how well it makes a master dark. Then, dark subtraction, flat subtraction (if using flats), aligned, optimized, stacked and waveletted in Registax. Save as tiffs again if your post processing program handles tiffs. Then reopen into your post processing package and complete your curves and levels adjustments.
Alternatively download IRIS (free) and download Jim Solomons Cookbook and give IRIS a go. Pretty steep learning curve but if you follow the Cookbook it will give you a good starting point.
Paul, do you have a link for Jim Solomon's cookbook? I downloaded IRIS after viewing the SDSS site and wanted to have a play. I can do the stuff in the projects that I've tried from SDSS, but when I try to follow the tutorials from the IRIS website, I don't seem to tbe able to hold my mouth right... Looks like a pretty powerful program once you get over he learning curve!
Please let us know how you go with Dark Frame subtraction. I am most interested. I have given up on trying deep sky stuff for the moment because I have a problem where the "black" sky ends up psychadelic colours after dark frame subtraction. I haven't sorted it out yet... I've just stepped back for a while to get some planetary imaging under my belt so it doesn,t get too frustrating... Still plenty of lessons fo me to learn!
I have had this problem too. Make sure the dark frames you are using have been taken with the same exposure time and ISO setting as the image frames you are using them on, preferably taken straight after you have finished capturing the images.
I once came up with the brilliant idea of combining all the dark frames I had ever taken into one master dark and tried to use it on an image ...... "WOW the background has gone all multicolored and green looking", I thought, "maybe that idea won't work then".
The dark frame is a representation of thermal noise in the ccd or cmos chip when the lens is capped, so to speak. As no light is striking the chip, what you are seeing is the thermal noise generated on the chip, as the chip pixels or charge wells register charges as if a photon has been captured at that point (as well as other artifacts such as cosmic ray strikes).
Thermal noise is halved with every 5 to 6 deg C drop in temperature, so you should try to capture dark frames at the same temperature as your light frame to avoid a mismatch. My SBIG ST7E ccd camera sets and regulates the temperature to within ± 0.1 deg C making it easier to capture darks at the same temperature as the light frame.
I once mistakenly subtracted a dark frame from a light frame at different temperatures, ending up with a final image spattered with black holes where “hot” pixels were subtracted which shouldn’t have been.
Thanks Middy and Dennis. Yep, I've eliminated all those issues... still have the problem. Thanks for the advice though! Now that I've learned how to process in K3ccd (done it once! ) I'm keen to maybe have another DSO attempt and see if I can subtract my darks with K3... just to try something different. If the problem persists at least I'll know it isn't software related.
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Registax is a pretty flexible program - there are lots of options, so it does seem a bit daunting first up.
I haven't sorted it out yet... I've just stepped back for a while to get some planetary imaging under my belt so it doesn,t get too frustrating...
Thanks for the advice though!
