Quote:
Originally Posted by Satchmo
Just having a look at your picture full size your system seems to avoid those unsightly halos around brighter stars evident in pictures taken with the Orion AG12. I suspect that the halos are caused by poor ghosting analysis in the design of the corrector ( but I'm open to other suggestions) , which the Keller corrector seems to be free of.
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Well Mark there is more to it than that actually.
Firstly
ghosting in a corrector lens system usually manifests in images as odd reflections that appear in the frame somewhere and not as halos around stars themselves...or perhaps you were referring to something else?
Halos around stars of various shapes and sizes can be caused by a number of things, including: the focuser barrel, adapters, chip cover slip, the CCD window, the filters or the corrector and the coatings on any one of the optical surfaces near the chip, or in some cases a combination of some or all these factors. As a result different combinations of scope corrector/flattener, filter, CCD window and chip cover slip give different results with different filter makes and even different filters within a single brand line.
The halos you are refer to in my images I have noticed are present most prominently when using the Ha filter and to a lesser extent the OIII and SII and they are weaker in the R G and B filters and basically non existent in the Lum. Now the intersting thing is that my Lum filter is a brand new not released Astronomik filter that Gerd Neumann sent me to try - this low halo effect is evident in my recent M7 image actually and I would say the degree of haloing in this bright star data set is no worse than many FSQ and other optical configuration images I have seen
If you also care to take a look at Adam Jesionkiewicz and Peter Shah's and
other AG users work who use various combinations of cameras, adapters and filter brands (but the same corrector), you will see your theory about the Orion Optics corrector being the culprit is likely not accurate.
Mike