close focus formula
- From: Tenifer <tensorsurfer@xxxxxxxxx>
- Date: Tue, 06 Nov 2007 20:40:00 -0800
There was this scope which can focus object less than a meter
from the object and you only have to move the focuser or mirror
a little bit. It was the MTO 1000 focal length f/10 4" russian
maksutov scope. I compared it with a 70mm F/8 560mm focal
length refractor and i have to move the focus back one foot to
achieve
close focus 2 meters away (in the refractor). Is there a formula
wherein I can calculate the exact back travel of the focuser to
achieve focus of the target say 2 feet away from the objective
of this 70mm f/8 560 focal length refractor given a
15mm plossl with magnification of 37X? I used paper
rolled into tube to extend the back focus a feet or a meter
away from the refractor rear but I can't achieve focus. Also why
is the maksotuv able to focus at one feet by just moving the
back focus a little bit like an inch??
Teni
.
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