The telescope was invented in 1608 by a Dutch
spectacles maker. He held a concave lens
(used for short-sightedness) in front of his eye
and a convex lens (for far-sightedness) towards
an object. With the correct distance between the
lenses he could see a magnied picture of the
object. Galileo Galilei was the rst person to use
a telescope for science in 1609. His telescope
design has the advantage of an upright picture,
but also the crucial disadvantage that the eld
of view becomes increasingly smaller with in-
creasing magnication. This is the reason that
today all astronomical refracting telescopes are
built according to the design of the great math-
ematician and astronomer Johannes Kepler. In
1611 he described a telescope that uses two
convex lenses, which allows high magnication
with a large eld of view. The picture is upside
down, but that is of course no disadvantage
for astronomical observations. This “Plumber‘s
Telescope” uses Kepler‘s principle too, but with
high quality achromatic lenses of which Kepler
wouldn‘t even have dreamt. The colour cor-
recting properties come from the combination
of two lenses with different refractivity which
are cemented together to form one achromatic
lens. Each of the parts on its own would have
great chromatic errors, in combination though
these errors cancel out.
This kit contains:
■1 achromatic lens, 40mm diameter, 450mm
focal length
■2 achromatic lenses, 15mm diameter,
26.5mm focal length, to build a Plössl eye-
piece with 15mm focal length
■4 pre-cut pieces of black cardboard
■1 tripod adapter
What you need for completion:
■1 piece of drain pipe, 40mm diameter, about
430mm long, preferably black, e.g. Mar-
ley/B&Q (for the telescope tube)
■ 2 push t couplings, 40mm, preferably black,
e.g. Marley/B&Q (to hold the objective lens
and the eyepiece)
■ 1 push t socket plug, 40mm (1 1/2”), e.g.
POLYPIPE WP30B (for the eyepiece)
■A small hacksaw to shorten the waste pipe
to the correct length
■A drill and drill bits to drill the 10mm hole of
the eyepiece (you can also use a nail or a
small cross headed screw driver to open the
hole and then widen it with a pair of scissors).
■Sticky tape for the eyepiece
■ Strong sticky tape (gaffer / duct / insulation
tape) to t the telescope to the tripod adapter
■Solvent-containing all-purpose glue (not
water based)
■A sharp knife (scalpel or small carpet knife)
■ A piece of ne grade sandpaper to smooth
the cuts
Assembly instructions:
Please always read completely through each
step before commencing.
A. The objective lens tube
The objective lens (or combination of lenses)
is the one pointing towards the observed ob-
ject, the one through which the light enters the
telescope. It ts just over the end of the waste
pipe and is secured in place with one of the
push t couplings.
Step 1:
Cut the waste pipe to 430mm ± 2mm using the
hack saw. To get a nice straight line at the right
length, wrap a piece of paper around the pipe
and mark the line to cut with a pencil along the
edge of the paper. Cut all around the line, not
just straight through from one side. Smooth the
