Back to Cygnus

[Knight of Clear Skies]

With Cygnus so well placed at the moment I decided to try it again at 50mm, with the goal of bringing out the Ha regions. To give myself the best chance I opened up the aperture a bit more, ran slightly longer subs and managed a longer imaging run from (I think) a slightly darker site. I also had the advantage of imaging in full astronomical darkness this time, with Cygnus traversing the meridian. Here's my work in progress image:

I was a little disappointed with the first result. Despite having more than twice as much data this time - 1 hour 30 minutes - after aligning the channels and stretching I was still left with a very monochromatic image. Boosting the saturation much left it looking quite odd. I then tried re-stacking with the previous session in a second group in DSS, giving over 2 hours total integration time. Again, the same problem.

Thinking it over, I suspect the problem is signal-to-noise. My unmodded camera blocks about three quarters of the Ha signal anyway, but the Ha-to-noise and LP ration will be far worse than this compared to a full spectrum camera at a dark site. So an LP filter might not only help remove gradients and capture fainter details, it may help me bring out the Ha regions too.

In the end I got a little creative. I took a copy of the red channel only and used the magic select tool to round up the nebulous regions, and blended it into the original image. It's not quite cheating - if I wasn't picking up the nebulosity I wouldn't be able to magic select them - but it's not quite right either. I couldn't select the faintest Ha regions this way where they blend into the background of the Milky Way, so there is a bit of an abrupt transition between the bright Ha regions and their surroundings. Hopefully I can manage a more subtle version. one idea I'm toying with is taking the red channel and subtracting the green channel from it, to produce a very crude Ha layer.

I feel I'm making some progress anyway. I've been working my way through some basic astrophotography and Photoshop tutorials and am slowly getting more comfortable with the it.

Image details:

~1 hour 30 minutes of data with 150 second subs at f3.5, 12 darks, 20 dark bias, no flats +

~35 minutes of 120 second subs at f4.0, 10 darks, 20 dark bias, no flats.

DSS was counting over 13,000 stars in the subs.

[bogdog]

nice capture again,been ages since i had a clear night here   and tonight its thunderstorms..yay me

[m37]

That is such a beautiful image, nice composition too. Lovely.

[greyhaven]

That's a wonderful capture of a very interesting section of the sky. I really must try some widefield AP. Thank you for sharing.

Grey