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does. A ashlight with a red LED light is ideal. Beware, too, that nearby porch,

streetlights, and car headlights will ruin your night vision.

“Seeing” and Transparency

Atmospheric conditions vary signicantly from night to night. “Seeing” refers to the

steadiness of the Earth’s atmosphere at a given time. In conditions of poor seeing,

atmospheric turbulence causes objects viewed through the telescope to “boil.” If

you look up at the sky and stars are twinkling noticeably, the seeing is poor and you

will be limited to viewing at lower magnications. At higher magnications, images

will not focus clearly. Fine details on the planets and Moon will likely not be visible.

In conditions of good seeing, star twinkling is minimal and images appear steady in

the eyepiece. Seeing is best overhead, worst at the horizon. Also, seeing generally

gets better after midnight, when much of the heat absorbed by the Earth during the

day has radiated off into space.

Especially important for observing faint objects is good “transparency”—air free

of moisture, smoke, and dust. All tend to scatter light, which reduces an object’s

brightness. Transparency is judged by the magnitude of the faintest stars you can

see with the unaided eye (5th or 6th magnitude is desirable).

Tracking Celestial Objects

The Earth is constantly rotating about its polar axis, completing one full rotation

every 24 hours; this is what denes a “day”. We do not feel the Earth rotating, but

we see it at night from the apparent movement of stars from east to west. When

you observe any astronomical object, you are watching a moving target. This

means the telescope’s position must be continuously adjusted over time to keep

an object in the eld of view. This is easy to do with the FunScope because of its

smooth motions on both axes. As the object moves off towards the edge of the

eld of view, just lightly nudge the telescope tube to re-center it. Objects appear to

move across the eld of view faster at higher magnications. This is because the

eld of view becomes narrower.

Eyepiece Selection

By using eyepieces of different focal lengths, it is possible to attain many mag-

nications or powers with the FunScope. Your telescope comes with two 1.25"

eyepieces: a 20mm, which gives a magnication of 15x, and a 6mm, which provides

50x magnication. Other 1.25" eyepieces can be purchased to achieve higher or

lower powers. It is quite common for an observer to own ve or more eyepieces

to access a wide range of magnications. To calculate the magnication of a

telescope-eyepiece combination, simply divide the focal length of the telescope by

the focal length of the eyepiece.

Telescope Focal Length (mm)

Eyepiece Focal Length (mm)

= Magnication

Orion FUNSCOPE User Manual

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