SKU 93233
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Page 6
Understanding the various parts in your kit
Before assembling any optical device, please read the instructions. The various
components work together in different ways to produce a specific instrument. 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
and concave on the other attached to it. The smaller flat/concave lens helps
sharpen the image seen through the double convex lens. When using Objective
Lens #8, the flat side is always pointed toward the object being observed. The
rounded, convex side is 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. This lens helps align
the image in the image plane, that means the image appears flat in front of the eye.
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
to bottom. Inversion lenses are used in “terrestrial” telescopes, which are used on
land. Without an inversion lens it might be confusing to see a bird on a branch
upside down. Inversion lenses are often not used in “astronomical” telescopes,
since stars and planets usually look about the same whether they are upside down
or not. Inversions in astronomical telescopes are confusing only when looking at
familiar objects like the moon. For that reason, some astronomical telescopes
include inversion lenses.
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.
Convex lenses bend light inward, and concave lenses bend light outward. When
used together at the proper focal length, they produce a magnified image with the
light in alignment again. This is the simple design that Gallileo used, and is the
basic refracting telescope illustrated on page 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
perception of an image being larger than it appears in nature. Magnification is
described as being so many times (“X”) its appearance with the unaided eye.
