SKU 93233
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Page 6
Understanding the various parts in your kit
Beforeassemblinganyopticaldevice,please read the instructions. The various
componentswork together in differentwaysto produce a specificinstrument. After
you understand how each of these parts works, you may experiment to find new
ways to put them together.
Objective Lens #8 is a magnifying lens. It is made of two lenses cemented
together.A lens which is convex on both sides has a lens which is flat on one side
andconcave on the otherattached to it. Thesmaller flat/concave lens helps
sharpentheimageseenthrough the double convex lens. WhenusingObjective
Lens#8, the flat side isalways pointed toward the objectbeing observed. The
rounded,convexsideis pointed toward the eyepiece.
Collecting Lens #4 is a combination of three lenses cemented together.A flat/
concave lens is nearest the objective. It is mounted onto a convex/flat lens which
has a flat/flat lens mounted on the inside nearest the eyepiece. Thislenshelpsalign
theimageintheimageplane,thatmeanstheimageappearsflatinfrontoftheeye.
Inversion Lenses #5 are used to turn the image right side up. A curious effect of
convex lenses like #8 is that, in addition to enlarging the image, they flip them top
tobottom. Inversion lenses areused in “terrestrial” telescopes,which are used on
land. Without an inversion lens it might be confusing to see a bird on a branch
upsidedown.Inversionlenses are often not used in“astronomical”telescopes,
since stars and planets usually look about the same whether they are upside down
ornot.Inversions in astronomical telescopesare confusing only when lookingat
familiar objects like the moon. For that reason, some astronomical telescopes
includeinversionlenses.
Eyepiece #6 is called a “diversion” lens because it bends light outward. It is a
concave lens that is used in combination with a convex magnifying lens like # 8.
Convexlensesbendlightinward,andconcavelenses bend light outward. When
usedtogether at the properfocal length, they producea magnified image withthe
light in alignment again. This is the simple design that Gallileo used, and is the
basicrefracting telescope illustrated onpage 5.
Eyepiece #7 is a “symmetric” combination of lenses. This consists of two sets of
opposite design lenses mounted in opposition to each other.The effect of this lens
is to magnify the image without distortion.
The Body, Drawtube, Eyepieces and Spacers are all provided to adjust the focal
length of any instrument you assemble from this kit. It is necessary to adjust the
focal length to result in an image in the eyepiece which is in focus.
A note on magnification. Magnification is produced by the interaction of lenses of
various sizes and shapes positioned in a certain relation to each other.It is the
perceptionofan image being largerthanit appears in nature. Magnificationis
describedas being so many times (“X”) its appearance with the unaided eye.
