California Nebula/Pleiades wide field

Discussion in 'Astrophotography' started by georgian82, Dec 17, 2015.

  1. georgian82

    georgian82 Mu-43 Veteran

    Jan 17, 2014
    Hi all,

    This is still a work in progress, but here it goes. It was taken with Olympus EPM2 and 25mm f/1.8 at f/4 and it consists of 42 x 3.5min exposures at ISO 800. It was processed in PixInsight with darks and bias frames.

    Cheers! California Nebula-Pleiades.jpg
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  2. TomG

    TomG New to Mu-43

    Jan 11, 2015
    Redwood City, CA

    Why did you stop down to f/4? I would think that would just make for longer exposures so you'd have more dark current noise.
  3. georgian82

    georgian82 Mu-43 Veteran

    Jan 17, 2014
    Hi Tom,

    I stopped it down to f/4 because this lens wide open suffers from vignetting and coma at the corners. Also, the stars don't seem to be as crisp as when stopped down. I can deal with vignetting post processing but I can only fix the coma by cropping the image which I don't necessarily like to do when is a wide field image.

    I did various tests with this lens by stopping it down incrementally and found that f/4 gave me the best performance image wise in at the expense of noise since I would have to take a longer exposure. That being said, I deal with noise by stacking and with dark frame subtraction which seems to work very well.