DS-3 and DS-4 have ended up being such successful homebuilt telescopes
that I decided to create a 20 inch homemade telescope using the same
ultralight design. This web page holds the results of these
Finished scope. This picture shows one of the design requirements - no need
for a ladder. When straight up, the eyepiece is 74" high, and I can use the
telescope flat footed up to 55 degrees from the horizon. A single step stool
works at the zenith.
Here the finished scope is stacked for transport. Another design requirement
is that the scope fits in the back of a hatchback.
Starting setup. Bearings are being attached to the mirror box.
The third design requirement is that I can move the scope by myself. Moving
the mirror box onto the rocker box. Mirror box, cell and 1 5/8" 20" mirror
weighs 55 pounds, and about 60 pounds with the bearings. Ground board and
rocker box are in the background. Also note that the mirror is covered and
Trusses go on the scope.
Secondary cage gets placed. Yet another design requirement is that the scope
be easy and quick to set up.
This next section details how I built the scope. It is mainly filled with
ideas and designs, not details. E-mail me if you have any questions.
Mirror cell parts. This will be an 18 point suspension. Point locations were
calculated using Plop.
Mirror cell parts put together.
Mirror cell parts painted.
Mirror box bottom, with cell laid in place.
Mirror box. Total dimensions are 22"X22"X5".
Mirror box and mirror cell. Total mirror box, mirror cover and cell weight
is about 18 pounds. The mirror ended up weighing about 37, bringing the
total to 55 lbs.
This is all there is to the ground board and rocker box. The reason that the
rocker box doesn't have a back (for stiffening) is so I can lift the mirror
box out of the rocker box.
The upper cage. A wire spider and homemade secondary holder was attempted,
but really didn't work. It had vibration issues that were unacceptable, and
mechanically was problematic. I finally went with a spider from
Astrosystems. The commercial secondary holder was 3" taller, necessitating
changing the cage from 6" tall to 9" tall.
The upper cage and trusses, together. My neighbor is in the background for
scale. The trusses are somewhere around 6" too long in this picture.
The total telescope in it's stored/travel configuration. The cement
mirror will be replaced with a quality mirror from OWL (Optic Wave Labs).
Once again, the secondary cage is 3" too short.
We now have some paint on the scope. Starting to take shape! The spider has
been replaced, due to vibration in the axis of the OTA.
Here I am next to the stored scope. This includes the base and rocker box,
with bearings removed.
Weight - Actuals
Mirror, mirror box, no bearings
Mirror, mirror box and bearings
Rocker box with base
of the OTA (Optical Tube Assembly)
of heaviest item (mirror and mirror box)
eyepiece at zenith
mirror box and base, secondary, no bearings
mirror box and base, secondary, and bearings