North America Nebula Mosaic
07 Aug 2023After a month of cloud, I finally got some sky time from 11:30pm until 3am. I decided that I’d take a gamble and try something different for this session. I imaged with my UHC filter in tandem with my IR cut filter. The reason I did this is that my UHC filter seems to let through too much IR which ruins the stars, so the IR cut will trim the top end. I noticed that a lot of UHC filters are advertised to be used in combination with an IR cut so I’m not doing anything weird. The idea of the UHC is to cut down on unwanted light pollution and focus on the wavelengths that matter. However, this means that light will fall on the red and green photocells in the camera sensor and the blue will be discarded. In effect I’m throwing away a quarter of my data which means my imaging session needs to be even longer. Hopefully this is offset by the quality of data that it actually collects.
If that experiment were not enough, I also decided that I wanted to image more of the sky than I could actually see with my camera. The only way to do this with my equipment is to do a mosaic of more than one image. I decided to start simple and take a 2 frame mosaic. So now my image time requirements have doubled again at a time when I’m not getting much sky.
Over the 3 hour session, I managed to get an hour of data on each mosaic frame however I discovered in post processing that seeing wasn’t as good as I thought it was so I had to discard a number of subs. In total, I got somewhere between 40 and 50mins on each frame.
The end result was a mixed bag. On one hand I’m pleased that I managed to suss out mosaic processing on the first attempt. On the other hand I’m upset that I couldn’t get more data. I’m still on the fence regarding this UHC filter. I’m not convinced that it’s giving me better results than just broadband. Perhaps I need a better filter? The final image is noisy and I stretched it as far as I dared. I then saturated it to death to get something interesting. What a frustrating hobby this is.
