Homemade eyepieces,
finder scope, and other misc accessories
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On this page
you can find instructions and ideas on how to make telescope
eyepieces, finder scopes and other misc accessories. A great source of inexpensive, surplus optics is Surplus Shed |
7x50 finder scope for 12$
Parts needed
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This is a 51 mm
diameter, 180 mm focal length , achromatic objective
lens. Cost : 6$
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Originally made as a
projection lens, it makes a very good 25 mm focal
length eyepiece. Cost: 5$
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A scrap piece of 50 mm PVC tubing (drainpipe) about 20 cm long, and a 50 -> 32 mm reduction fitting Cost: 1$
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The lens body has an
outer diameter of 25 mm. To convert it to a standard
1.1/4" eyepiece size, cut a cardboard strip, and glue
it around the bottom (widest) part of the lens. Take
a Kodak film canister, and cut of the bottom . Now
put the lens inside the film canister.
This lens is also good as a telescope eyepiece. If you have a smaller telescope with a 0.96" focuser, you can use this lens as a primary eyepiece. A minute with fine sandpaper on the focuser inside, and it will fit perfectly. Optically, it is by far superior to the usual H20 plastic lenses eyepiece, originally received with the telescope. |
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To assemble the
finder scope, first measure the length of the 50>32 mm fitting
with the eyepiece lens inside. Leave 5 mm spare, for fine focus. |
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Total length of the finder scope for focus at infinity should be
218 mm, from objective lens, to eyepiece end, so cut the 50 mm
tube accordingly. Connect the plastic tubes, paint the inside flat black, and the outside in any color you please :) You can fasten the objective lens at the front by simply winding a few turns of electricians tape around the lens edge and tube. The finished finder scope mounted on the telescope. You can fine focus the finder scope by moving the eyepiece inwards or outwards inside the 32 mm tube. This is usually referred to as a draw tube focuser. |
Illuminated finder
scope
Can't see the
black crosshairs against the dark background of space? A ready
made illuminated finder is too expencive?
All you need is a 3$ reticule, a LED, 2 AAA batteries, and some
electronic components from the "junk bin"
Even just two hairs instead of the reticule will work perfectly
26 mm super Plössl eyepiece
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This
is the "26 mm SuperPlössl eyepiece kit" from
Surplus
Shed Cost is 6.5$ |
Materials needed
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26 mm SuperPlössl eyepiece kit |
32 mm PPR fitting | |
2 Kodak film canisters, black electricians tape, superglue |
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This is a 32 mm PPR
water pipe fitting. The inside diameter is 30 mm, and
it needs to be bored to 1-1/4" (32 mm) A Forstner bit
is ideal for this. It can also easily be done on a
lathe if you have access to one.
The felt pads are temporary, they are used not to scratch the PPR fitting in a vice or lathe while drilling. |
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With a
sharp utility knife , we cut off the upper rim of the
film canister (around 5 mm), and a 30 mm piece. |
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Conveniently enough, the achromatic lenses fit perfectly inside the film canister, and the film canister fits perfectly inside the PPR fitting Use the 30 mm canister section and place the achromatic lenses (thick ones) inside...... |
...then put the canister part with the lenses inside the PPR fitting. Use some electricians tape for a snug fit if necessary...... |
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..now
put the eye lens (single lens) on top, with the
flatter side turned upwards, then add the top part of
the film canister as a lens retainer. Use a drop of
superglue on the upper rim of the canister. Now,
insert the 40 mm , barrel section on the bottom side,
use electricians tape and a drop of superglue to
secure. Done :) Lenses orientation in the "26 mm SuperPlössl" eyepiece |
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This eyepiece has a generous eye relief of aprox 20 mm and has aprox 55°apparent field of view
19 mm Plössl eyepiece
![]() Even simpler is the 19 mm Plossl eyepiece kit . It costs 5.50$ |
Lenses orientation in the 19 mm Plossl eyepiece.
Cut a 5 cm strip of black electricians tape, put it on the desk with the adhesive surface facing upwards. Roll the 2 lenses over the tape and it winds itself around. Put the lenses in the PPR fitting. Plug the fitting into a Kodak film canister with the bottom cut off. Done :) |
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In addition to the lenses you receive from Surplus Shed you only need a 20->25 mm PPR fitting adapter, a Kodak film canister, and a bit of black electricians tape. |
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© 1999-2005 Berislav
Bracun
Amateur telescope making, star charts, planisphere, astronomy
software, eyepieces, findescopes, observing
accessories