JohnP_1

The Rosette nebula - a rose like none other

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by , 01-28-2019 at 12:02 PM (55 Views)
Quote Originally Posted by CamelHat View Post
Really good image John! Let me get this straight: you used only 35 minutes integration time, with what sensor? The Atik383+ OSC? I need to get me one of those...
Here is a screen shot of a lightly stretched original frame. No preprocessing steps were taken on this image, and the light pollution is still evident. I performed an adaptive bin within Nebulosity and DDP stretch with some curve manipulation. No NR applied to this frame. During preprocessing of the posted image, I used recycled flats, bias and a "bad pixel map" dark frame substitute that Nebulosity uses during it's preprocessing work.

The Atik suffers from a lot of hot pixels, which has become the primary goal of the number of successful frames that I collect. I like to have enough frames to improve the SNR by a factor of 2 to 3 or better.

The image resolution was 1.96 arcsec/pixel. The guiding ratio was 2.46. Polar alignment was setup using the Pole Master on that night, which has been far better behaved once I learned how to keep Windows from shutting down the USB port... (I was very close to throwing away the Pole Master because I thought it was trash.)



Screen Shot 2019-01-28 at 6.44.49 AM
by John Pombrio, on Flickr
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  1. JohnP_1's Avatar
    The long specification for the Atik's sensor (KAF-8300L) lists the Quantum Efficiency for the RGB channels as 33, 40 and 33%. Practically speaking this helps produce a decent balance in the color in the raw images as compared to my AP modified DSLR, which tend to be very sensitive in the red. (I think even a bit more sensitive than the Atik.)

    On this particular target, the (more sensitive) green channel was almost non-responsive. The histogram peak for green was fairly narrow (low LP) and very steep. The blue channel was more responsive, though it mimicked the green. The red channel was the primary response and a grayscale image of just the red would make a decent false luminance.
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