Re: ATM - a 'scope for the classroom

["Tom & Lou Krajci" <krajcit@3lefties.com>]

From: Adam Perkins <scopeguru@yahoo.com>

>I've decided to build a scope for my wife's Sixth-Grade students.  She
>and I figured that they could borrow it for a week or two at a time,
>and get some fun out of it.

>- - a long (f/8-10) focal ratio for good performance with cheapo
>eyepieces and poor collimation

>- - a dobsonian mount for durability and ease of use

>- - 4-5" newtonian optics, big enough to see some neat things, but small
>enough for a kid to handle and me to afford

>I already bought a secondary mirror and a cheap eyepiece just for this
>scope.  I will probably add an old 6x30 finder I have.

>Has anyone reading built a "public" scope before?

I built a few club "loaner" scopes for the Shreveport-Bossier Astronomical
Society last couple years, when I was still stationed at Barksdale Air Force
Base.  A bunch were f/10.5    4 1/4" dob-newts.  At public star parties the
kids loved them with an inexpensive low power eyepiece giving about 55x.  We
had a length of six inch PVC tube lying around that I cut into scope tubes
about four feet long.  Thick wall and kinda heavy, but very durable!  These
4.25" scopes were good optical performers...white ovals on Jupiter, Cassini
division in Saturn's rings, supernova in some NGC galaxy last spring (near
Chi UMa).  The six inch scopes performed even better.

Make sure the upper end of the tube is long enough, or has a long enough
dewshield, so that young, curious fingers don't get chocolate fingerprints
on the secondary mirror!

Good luck!  Tom Krajci