1200mm: Digital Teleconverter

Started 7 months ago | Discussions thread
MHshooter Senior Member • Posts: 1,010
Re: Used Canon 1200mm for $180,000

8 inch wide front element at f/5.6 means you are at the mercy of horrifically-magnified heatwaves over the distances that thing is meant for.  You'd be luck to achieve it's full resolution wide open a fraction of the time is was used.  I've got an SCT 8" telescope.  With a focal reducer/field flattener, that becomes 1250mm f/6.3.  But using such an optic in the daytime is pretty much a waste.  However, if the diameter of whatever optic you are using is reduced to 4 inches wide or less, it will produce on average steadier images.  So, the Canon probably works best around f11 most of the time.

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