Cooling The Telescope; Astronomical Observing - Orion SpaceProbe II 76mm Instruction Manual

Yoke Mount
Hex-shaped hole
Tripod
leg
a.
Figure 5.
a) Attach the three tripod legs to the yoke mount,
making sure the bolt's hex-shaped head seats in the hex-shaped
recess of the tripod leg. b) Place a washer and wing nut on the
exposed end of the bolt.
the finder scope is properly aligned with the telescope.
The red dot finder scope's alignment should be checked
before every observing session.
At the end of your observing session, be sure to slide the
power switch on the red dot finder scope to OFF to preserve
battery life.
Understanding the "Altazimuth" Mount
The SpaceProbe II 76mm Altazimuth Reflector features an
"altazimuth" mount, which permits motion along two perpen-
dicular axes: altitude (up/down) and azimuth (left/right) (see
Figure 2). This makes pointing the telescope easy and intui-
tive. To move the telescope in the azimuth direction, loosen
the azimuth lock knob, take hold of the telescope and gently
rotate it to the desired position. Then re-tighten the azimuth
lock knob. To move the telescope in the altitude direction,
loosen the altitude lock knob then move the tube up or down
to the desired position. Then retighten the altitude lock knob. If
the telescope moves too freely in the in the altitude direction,
then tighten up the yoke knobs a bit. Of course, you can move
the telescope in altitude and azimuth simultaneously by loos-
ening both of the lock knobs.
Because making fine-adjustments in the altitude of the tele-
scope can be difficult, the SpaceProbe II 76mm comes equipped
with an altitude micro-motion rod and thumbwheel (Figure 13).
After making coarse altitude adjustments by moving the tube
by hand, you can then move the telescope incrementally by
turning the micro-motion rod's thumbwheel (the altitude lock
knob must be tightened for this). The telescope will move a
very small amount either up or down, depending on which
direction you turn the thumbwheel. Fine motion can be helpful
when centering an object in the eyepiece

4. Astronomical Observing

For many, this will be your first foray into the exciting world of
amateur astronomy. The following information and observing
tips will help get you started.
Washer
Wing nut
b.
Choosing an Observing Site
When selecting a location for observing, get as far away as
possible from direct artificial light such as street lights, porch
lights, and automobile headlights. The glare from these lights
will greatly impair your dark-adapted night vision. Set up on
a grass or dirt surface, not asphalt, because asphalt radiates
more heat. Heat disturbs the surrounding air and degrades
the images seen through the telescope. Avoid viewing over
rooftops and chimneys, as they often have warm air currents
rising from them. Similarly, avoid observing from indoors
through an open (or closed) window, because the tempera-
ture difference between the indoor and outdoor air will cause
image blurring and distortion.
If at all possible, escape the light-polluted city sky and head
for darker country skies. You'll be amazed at how many more
stars and deep-sky objects are visible in a dark sky!
"Seeing" and Transparency
Atmospheric conditions vary significantly from night to night.
"Seeing" refers to the steadiness of the Earth's atmosphere at
a given time. In conditions of poor seeing, atmospheric turbu-
lence 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
magnifications. At higher magnifications, 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 over-
head, 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).

Cooling the Telescope

All optical instruments need time to reach "thermal equilibri-
um." The bigger the instrument and the larger the temperature
change, the more time is needed. Allow at least 30 minutes
for your telescope to acclimate to the temperature outdoors
before you start observing with it.
Let Your Eyes Dark-Adapt
Don't expect to go from a lighted house into the darkness of
the outdoors at night and immediately see faint nebulas, gal-
axies, and star clusters—or even very many stars, for that mat-
ter. Your eyes take about 30 minutes to reach perhaps 80% of
their full dark-adapted sensitivity. As your eyes become dark-
adapted, more stars will glimmer into view and you'll be able
to see fainter details in objects you view in your telescope.
To see what you're doing in the darkness, use a red-filtered
flashlight rather than a white light. Red light does not spoil
your eyes' dark adaptation like white light does. A flashlight
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