Jelly fish and Monkey Head wide field

Discussion in 'Astrophotography' started by georgian82, Apr 8, 2016.

  1. georgian82

    georgian82 Mu-43 Regular

    119
    Jan 17, 2014
    This was taken with a modified Olympus EPM2 and Sigma 60mm f/2.8 at f/2.8 and ISO 800. It consists of 73 x 3 minute sub frames with dark and bias frames subtracted. I placed the camera in a homemade thermoelectric cooling box and I removed the back screen in order to make a better temperature drop. This took me three days of imaging and the outside ambient temperature ranged from 9C and 12C and the actual sensor temperature got down to -5C and -1C according to the exif data, thus reducing thermal noise substantially.

    These nebulae are very dim and I was shooting in an area of the sky that has a lot of light pollution, so it was a real challenge to get much detail and contrast from the raw files.

    Cheers!

    Jellyfish and Monkey Head 5.
     
    Last edited: Apr 8, 2016
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  2. maritan

    maritan Mu-43 Veteran

    388
    Oct 30, 2014
    Good work. Looks like your experimentation is really paying off.
     
  3. georgian82

    georgian82 Mu-43 Regular

    119
    Jan 17, 2014
    Thanks! Yes, I would say it is working very well so far. There are a few things in the design that I need to address but otherwise it does what is supposed to. It is unfortunate though that is necessary to take off the screen (if the camera) in order to achieve a good temperature drop, but I guess that's the price I pay if I want longer exposures and less noise.

    Cheers!
     
  4. maritan

    maritan Mu-43 Veteran

    388
    Oct 30, 2014
    Just thought of something - you need focus at infinity, correct? Have you just set that point on the lens and taped it down, so it doesn't change? I assume without a screen focusing might be a tad bit challenging?
     
  5. georgian82

    georgian82 Mu-43 Regular

    119
    Jan 17, 2014
    image.
    I use a bahtinov mask to focus. Using live view is fairly easy. I focus with the screen on, then frame and then remove the screen before beginning taking pictures. The problem is that the focus tends to change when the temperature drops too much. I don't tape the lens after finding the focus point but I should.

    Cheers
     
    Last edited: Apr 8, 2016
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