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Wonderful image as usual Mike. If I was you I would get an aperture laser cut to mount immediately in front of the first element in your 152mm APO. You would only have to reduce the native aperture by a few mm. The flare around the bright stars are caused by inhomogeneities (differences) of the edges of the first element holder. This causes very slight scattering and diffraction that is non uniform. It is even worse as your camera gets more sensitive, as even the slightest or weak faint aberrations are beautifully recorded when the source is a very bright star.
Televue has been doing this for years by blackening the edges of all lenses in their eyepieces.
If you do not believe me just do a test with a bit of very black paper or card as an aperture smaller than the entrance of your fine 152mm APO.
Bert
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