Saturn was low on the horizon and lights from the school likely added light artifacts to the image I was seeing.
The dome cut out all the outside light from the low lights and this gave a big advantage to the C 14.
I'd post more but I'm fairly brain dead at this time and need to get some sleep.
Shot of the big shootout below. Didn't have any visitors during the time I was there and this allowed me to take some time taking mostly night photographs. I tried to take some photos of Saturn with the camera on the 2 inch guide scope on the Big Newtonian but I ran out of time and didn't get any decent shots worth posting of Saturn.
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ReplyDeleteA quick explanation of light pollution localized that affected my image.
ReplyDeleteThis kind of Newtonian has a corrector plate.
It's only 4 or 5 inches inside the tube.
The angle of the stray light from a streetlight hits the corrector plate much easier than it would if it had to. Travel down a dark tube and hit the primary mirror. This light causes stray glow to come from the corrector plate.
If this was a long and narrow Newtonian with no corrector plate, like a f8 of f10 four or six inch Newtonian, it would be likely that none of the glow from the nearby streetlight would reach the back mirror. For very bright urban locations you could get a darker image with a long small Newtonian with a good flocked tube. (flocking is coating the inside of the tube with non reflective material).
Flocking a Newtonian with a corrector plate would likely not help much, because the light hits the corrector. So a telescope with a corrector would perform and deliver darker images in a location with less lights. You'd see a greater improvement at a dark sky site and conversely poorer performance with many street lights.
But in this case the nice extra on the big newtonian that normally gives a better image will give more extra light glow mixed into the resulting image. This will reduce the quality of the image.