The Idea
As an astronomy educator, I sometimes find things that have much
more potential than they initially appear to. Take, for instance, the little cardboard
tube telescope that Learning Technologies produces. This is designed to introduce young
people to basic telescopic optics. The resulting scope is about equal to Galileo’s
first telescope. The problem is, that’s all you get, a scope. It gives you the basics, but
if you want a student to really have a useful instrument, you have to find a better way to
use that telescope. There are also a lot of small “trash telescopes” out there that are
pretty much in the same range, about 40 to 50 mm. Their optics are pretty decent, but
the mounts they come with leave a lot to be desired, being too flimsy and shaky.All
they need is a better mount to be a good introductory tool. If you have access to
a sturdy camera tripod, you have the beginnings of the solution. What you need is a
cradle to hold the optics.
Building the “Lil’ Mount”
For a modest outlay of money and expenditure of time, one can build
a mount that can handle small scopes up to 50 mm. No major woodworking skills are needed,
just the ability to cut a fairly straight line. Most of the materials can be
found at a craft store, with only a side trip to a hardware store.
(Click On Images for Full Size)
To build the mount, you’ll need the following –
Materials -
3/16” x 3” x 36” (4.5 mm x 75 mm x 900 mm) balsa
3/16” x 36” (4.5 mm x 900 mm) hardwood dowel
Felt sheet
¼” (6 mm) nut
Steel washer
Two rubber bands
Tools –
Razor knife (a box cutter will do)
Ruler or straight edge
Emory boards
Small rat tail file
Scissors
Aleene’s Craft Glue (or equivalent, such as wood glue)
“Invisible” tape
Cut out all of the balsa parts using the pattern and straight edge. Carefully cut out the hexagonal opening in the base. Cut an emory board using the scissors so that you end up with a couple of ¼” (6 mm) “files”. Use one of these to smooth up the hexagonal opening, enough that the nut will fit snuggly into it. Apply a liberal amount of glue to the top bolt cover and, centering it, glue it to the base so that it covers the nut. Make sure that the grain runs in the same direction as the base. Using the rat tail file, drill out the opening in the bottom bolt cover so that it is a little over ¼” (6 mm) wide. Apply glue over the bottom bolt cover and attach it to the bottom of the base so that it covers the nut but so that the openings line up. Cut a piece of felt 1 ½” x 2” (38 mm x 50 mm) and cut a ¼” (6 mm) hole in the center. Now glue the washer in place, apply glue to the bottom bolt cover and glue the felt so that all of the holes line up. Set completed base on a hard surface and put a heavy object (such as a book) on top of it and allow it to dry. Drill out the two opening on the rear support using the file so that the dowel slides in smoothly. Now glue the two supports to the both ends of the completed base, making sure that the rear support holes clear the wood. Attach the braces so that they are flush to the sides of the base and the supports. Allow this assembly to dry overnight. Use tape, if necessary, to insure that all parts are lined up and held together while they dry. Once it has thoroughly dried, cut two strips of felt and glue them to the “V” notches in the supports. Trim after they dry. Now, glue the solar screen braces to the inside of the rear support braces (make sure that they don’t interfere with the holes in the rear support). Glue the solar screen mount between the solar screen braces, leaving about a 3/16” (4.5 mm) gap on both sides (this is important!). Finally, glue the solar screen mount top over solar screen mount and braces, making sure that the grain runs perpendicular (across) the base grain.
To make the solar screen, cut the dowel into two equal pieces 18” (45 cm) long. Using the remaining balsa, cut a rectangle 3” x 6” (75 mm x 150 mm). Use the rat tail file to drill two holes centered 1 7/8” (48 mm) apart, so that the dowels fit snuggly. Cut a 3” x 5 ½” (75 mm x 135 mm) rectangle of poster board and glue it to the front of the balsa “screen”. Lay the screen face up and glue the dowels into the holes and let dry.
Using Your “Lil’ Mount”
Mount the telescope so that it rests in the “V’s” in the supports. Take the rubber bands and put them around the scope and the mount so that it is held firmly in place. Now you can attach the mount to a tripod just as you would a camera. To do solar observing, simply slide the dowels of the solar screen into the holes on the back of the mount, making sure that the screen is up. If necessary, make a sun shield that fits around the scope using the poster board (see image). Just make sure that YOU DO NOT LOOKAT THE SUNWITH YOUR SCOPE! THIS IS DANGEROUS TO YOUR VISION AND CAN RESULT IN PERMANENT LOSS OF SIGHT! Instead, project an image of the Sun on the screen.
There are a lot of possibilities with the basic mount design. It might
be possible to make a sturdier mount using a harder wood. This might even be a larger
mount for larger telescopes, replacing the rubber bands with a “top” that might
be held down with something like bolts. Play with the design, have fun.
