SCT Focal Reducers and Vignetting (explained)
To be precise -- A focal reducer takes the image and makes it *smaller* and
brighter.
So an image that would have been 2 inches in diameter gets shrunk down to
something smaller.
And it was 2 inches in diameter because of the size of the internal tubes in
the telescope.
I find it puzzling that people don't expect vignetting. Of course there's
vignetting. If you take a full-page document to Kinko's and get it reduced
to 4x6 inches, the adjacent pages don't magically appear next to it!
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