Quote:
Originally Posted by gregbradley
I used to see something similar on the CDK17. Planewave sent some 3D printed baffles for the corrector and around the central tube and it stopped them.
So if the filter does not work then I would suspect you need a baffle or two similar to the Planewave.
Greg.
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Quote:
Originally Posted by Peter Ward
I have seen something very similar. before.
Almost certain this is an internal baffle reflection.
located close to the back plate of the 'scope....probably off a black (but still shiny) anodised surface.
Nothing some matt black acrylic or flocking material ( honest... I am not cursing ) will not fix in a jiffy.
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Thanks Greg & Peter,
Done a lot of thinking about this!
I'm pretty convinced now that my artefact coming from the Mag 1 star that's only 1 degree away from the imaged field. The arc's focal point is roughly indicating the position of that star. I THINK this means it is an extraneous light problem as opposed to an internal reflections.
I initially (2013) had severe problems with flaring almost all the time because they mounted a new design flattener further forward than usual.
See the first image below - the
red ray indicates the problem. They responded with a clever and novel primary baffle extension (See the
pink component
in the middle image below) which totally eliminated extraneous light impinging on the flattener lens. Alas, it had the side effect of adding glare around stars (bloating them) and raising the background level either by diffraction or grazing incidence of light from the primary on the "matt" surface of the extension (or both).
I experimented with adding my own baffle extensions to make the secondary baffle larger and the primary baffle a bit longer (both using flocking board).
See the 3rd image below. I've been operating like this since 2014 without problems (beyond incleasing the obstruction and perhaps a tiny bit more vignetting.
So, as you can see from the 3rd image there is still the possibility of extraneous light hitting the edge of the flattener lens. I do have a home made matt black baffle ring down there, but it may not be sufficiently broad. I'm loathe to make it bigger though. Before I go taking the camera off and looking for shiny stuff I think I'll lengthen my primary baffle extension - I can just pull it out a bit.
Having said all that, a star only 1 degree away does suggest it's light is travelling down the whole optical path in which case it's a scattering / reflection problem from something in the imaging train = look for shiny things in the imaging train!
BTW Peter, I already have little cylinders of flocking board in the imaging train and close to the flattener. That doesn't mean I don't need more of course.