Challenge: Measure the diameter of a crater on the
moon. We can’t get to the moon - unlike Kathy,
Iain, and Kate are going to Meteor Crater in Arizona
- so Jonathan and I are going to make a telescope out
of mirrors from the trunk.
Given good mirrors- something we couldn’t make
in three days
Collect a lot of light- bright so we are able to see
Increase magnification- big mirror and an eyepiece
Secondary challenge: Make soft-light candles to work
by at night while making measurements of the diameter
of a crater on the moon.
Strategy: Collect pine resin, make a wick out of sagebrush
Discuss telescope and mount design with Jonathan. We
decided there was no need to enclose the telescope because
we are using it in the dark. Plus, having it open allows
everyone to see exactly how the telescope works. The
stability of the mount is crucially important because
when we magnify stuff even the littlest shake makes
a big difference. We want an accurate measurement of
the diameter of a crater on the moon - no wiggle allowed.
Setting up the telescope: First, we found the focal
length of the telescope. Then, using similar triangles,
Jonathan and I figured out where to put the small (1
inch) mirror, which will divert the image to the eyepiece,
where it will be magnified further. (Yes, we are using
inches. Some areas of science just haven’t switched
The 6 inch mirror has a focal length of 48 inches.
Our 6 inch mirror is a concave mirror, a parabolic shape
that collects light. Light travels in straight lines,
hits the mirror and comes to a point—the focal
point of the mirror.
We use strips of an old California car license plate
to hold the small mirror in place. Because we are looking
far, far away (the moon) and because light travels in
straight lines from all points, it is okay to have the
thin metal strips in front of the mirrors. They don’t
block very much light and they are much better than
putting one’s head in front of the mirror—which
would make the telescope completely ineffective!