Really nice shots, Gabor. And wish you luck with the rehousing project! Mine now looks as this, but I'm already thinking of rehousing it (anamorphic slider focus, taking lens with focuspull). Minimum distance without diopter =100cm (from object to taking lens, where SUN is attached), shown in shortest f_length (a portion of thread and brass guides shaved off):
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And there's an option of sticking Canon 2xB-extender behind FD 1.8 50mm. Regular Lumix 14-42mm still has much of vignetting...