Re: Focuser extension into tube
Mel Bartels (mbartels@efn.org)
Wed, 8 Mar 95 00:01:33 PST
JMI-1 2" that I have has a typical extension of maybe 1" below the base.
Assuming 1/4" tube thickness, this means 3/4" remaining. However, the upper
end should never be so 'tight' that there is no allowance for off-axis light
for objects at the extreme edge of a low power field of view. This
typically means a tube id a couple of inches larger than the mirror
(necessary if you used a closed tube for ventilization purposes). So, the
focusing tube would never stick into the on-axis light.