Coleman AT70 - Using Your Telescope; Terrestrial Viewing Note

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E. USING YOUR TELESCOPE:
1) It is recommended to use your telescope outside or at times through open windows. Your
view can be distorted by reflections in the glass of a closed window or at times by air
currents of differing temperatures passing through an open window.
2) Let your telescope adjust to the outside temperature. Your telescope will perform
much better if the temperature of the mirrors, eyepiece lenses, and the air inside the
tube are the same as the outside temperature. It may take up to 30 minutes to
equalize the temperatures when the difference in temperatures is extreme.
3) Find a location far from glaring light. If you live in an urban area, your viewing will probably
improve the farther you move away from the city’s lights. The sky glow of a town or city can
dramatically reduce the telescope’s performance and viewing capabilities.
4) Remove the dust cap from the end of the telescope. The open end of the optical tube
should be pointed toward the subject you wish to observe.
5) Begin your viewing session by using only the K25 eyepiece. It will give you the widest
angle and the brightest, sharpest views. Adjust the angle and position of the telescope as
outlined in the previous sections.
When possible, avoid sudden temperature changes, as the moisture in the air will condense
on the mirrors and eyepiece lenses. Should this occur after bringing your telescope indoors,
remove the dust caps and allow the moisture to evaporate naturally. Point the telescope
downward to minimize the collection of airborne dust. Once all of the moisture has
evaporated, replace the dust caps.
F. A NOTE ON TERRESTRIAL VIEWING:
When viewing through a standard telescope, you may notice that when you observe a
terrestrial object on land or water it appears upside down.
To correct this, the COLEMAN AT70 is equipped with an erecting diagonal prism (4). This
accessory is inserted in the eyepiece holder of the telescope between the eyepiece and the
telescope. With the erecting image diagonal, objects will appear in their proper orientation for
terrestrial and land observation.
NOTE: The eyepieces must be used together with the erecting diagonal prism.