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Hi Jo, that is a beautiful shot. *Edit, found NGC3324 NGC3293.*
The bloated stars on the left hand side of the frame is due to the secondary mirror being slightly out of collimation so the light strikes the focal plane at an angle, making the focus different for each side of the frame.
One of the "joys" 'cough' of making one's own newtonian scope (I've made a dozen and still have trouble getting them perfect) is getting the secondary in the correct position. They look okay for visual use, but the slightest shift will show on a photo. For photography they have to be perfect! In your case it looks like the secondary may be too far from the primary. Screw out the center screw on the secondary holder a couple of turns, re-collimate and do a quick single frame to test. Or I might have that backwards LOL. We're only talking maybe 1 mm or so here.
Here is a pic through my 6 inch F6 home made Newt of Miaplacidus with the same problem but opposite side.
For perfect stars all across the frame an F6 Newt still needs a field flattener but it won't be as extreme as a faster scope.
Last edited by cometcatcher; 11-02-2014 at 11:24 AM.
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