The Galileoscope
• A simple refractor that can be configured to
simulate what Galileo saw through his
• Re-creates the wonder Galileo must have felt
when he became the first to view the sky
through a telescope
• Can be used to demonstrate how telescope
optics work
Let’s Build It….
Step 1
Lay out one half of the main telescope tube, open-half up
Step 1
Examine the objective—the large, main lens. Note that it is
actually two lenses fused together, one thicker than the other.
Step 1
Without touching the face of the glass, snap the objective into
the slot at the large end of the main tube, thinner lens closer to
the end
Step 2
Seat the hexagonal nut into the half-hex hole at the central
mount. Make sure one point faces upward.
Step 3
Lay out the two smaller focuser-tube halves with the glossy and
textured inner faces next to each other. Note the “U” holes.
Steps 4 and 5
Keeping the gloss and textured sections at the same ends, fit the two
halves together and slide on the end cap with its narrower lip toward
the U-holes. Stretch on an o-ring at each end to fasten the tube.
Step 6
Baffles
Lay the focuser tube into the narrow end of the main tube half,
U-holes and end-cap facing out, and the other end between the
two baffles in the main tube half.
Step 7
Adhere the Sun-warning sticker to one of the main telescope
tube halves.
Step 8
Fit the other main telescope tube half over the first, snapping it
into place around the objective. Make sure the focuser tube end
clamp remains outside of the main tube assembly.
Step 9
Pressure-fit the focuser tube end cap onto the main telescope
tube end, and the large front-cap/dew-cap onto the objective
end.
Step 10
Optionally, you may wrap the other (larger) o-rings around the
outer grooves of the main telescope tube.
Step 11
Of the six small eyepiece lenses, remove and examine the four
larger ones. Try not to touch the surfaces of the lenses.
Step 11
Two of the lenses are double-convex. These will magnify
objects like a normal magnifying glass.
Step 11
The other two lenses are plano-concave: one flat side and one
concave side. These will make objects look smaller.
Step 12
The eyepiece lenses fit together: one convex face and one
concave face fit together to make a pair (left).
Place the two paired lens sets into the slots of one of the main
eyepiece housing halves, with the convex lenses facing each
other (right).
Step 13
Slip the small black plastic ring (light baffle) into the narrow slot
at the other end of the main eyepiece housing half.
Step 14
Add the second half of the main eyepiece housing to the first.
Attach the thin black end ring to the narrower end of the
eyepiece, and the thicker ring to the wider end with the
smoothly rounded edge facing out.
Step 15
The main eyepiece, which will give 27x magnifying power when
inserted into the focuser tube, is finished.
Step 16
Now, remove and examine the two smaller eyepiece lenses.
One is plano-convex (one flat side and one concave side) and
the other is double-concave (two concave faces).
Step 16
The plano-convex lens magnifies objects, while the doubleconcave lens makes them look smaller.
Step 17
Fit the convex side of the plano-convex lens into a concave side of the
other lens and place them in the slot in one of the auxiliary eyepiece
holder halves. Make sure the double-concave lens faces the narrower
end of the auxiliary eyepiece holder.
Steps 18 and 19
Fit the other half of the auxiliary eyepiece holder to the first,
and snap the black end-ring over the wider end. Make sure the
two eyepiece lenses remain seated in their groove.
Steps 20 and 21
Fit the narrow end of the auxiliary eyepiece into the narrow end
of the Barlow holder tube, and then fit the main (27x) eyepiece
into the wider end.
Steps 20 and 21
Push both eyepieces firmly into the Barlow holder tube. This
completes the Barlow lens configuration, which will give a
magnification of 50x when used in the Galileoscope.
Steps 23 and 24
Remove the auxiliary eyepiece from the Barlow lens assembly
and snap on the thick, wide eyepiece cap to its narrow end.
This creates the “Galileo” eyepiece that will produce upright
images at about 18x magnification—approximating what Galileo
experienced through his telescope.
Done
Contacts
Ben Burress, Chabot Space & Science Center
[email protected]
Edna DeVore, SETI Institute
[email protected]