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Old 11-06-2007, 07:49 PM
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bojan
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Join Date: Jul 2006
Location: Mt Waverley, VIC
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Well, halo of this nature is usually the consequence of spherical aberation or internal reflections in the optical system.
It seems to me the latter may be the case, the focal reducer being not properly corrected or coated for IR part of the spectrum, and the fault becomes visible when you removed the IR filter.
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