Quote:
Originally Posted by iceman
Thanks David and Phil.
Phil I wish you could've been there too - hopefully next year?
Phil I tried dark frames a couple of times, but my darks never properly matched the lights for some reason - temperature difference? So when I subtracted them, I ended up with holes in my nebula.
So since then, I've always done them in-camera. I really love the results of it, but like you say - it's a whole lot of sky time where the camera isn't taking exposures.
Maybe I should give separate darks another try.  |
Do you know the dates for IISAC next year yet? I need to plan some other committee meetings around it so I can be there!
And you should definitely investigate this darks issue further.. something is wrong if you can't take a series of darks and subtract them with a better result. try sending me some light and dark frames (eg yousendit.com) if you want me to test the processing with ImagesPlus.
you should also be able to do an extreme stretch of a master dark frame and see if it looks right or contains other artefacts before you subtract it.
For the benefit of others.. in camera darks subtract a single dark frame from the light frames. While this will remove the hot pixels, it will actually contribute more random noise to the image, making it [very slightly] worse than using no darks at all. By taking a large number of darks at a convenient time at close to the same temperature (i have never had any serious problem with only 'approximately' the same temperature), averaging them all together and then subtracting those, you should get a better result than in camera dark frame subtraction. and you won't waste half your dark sky time with dark frames - doubling your exposure time is more important than the dark frame calibration anyway!
phil