Orion SPACEPROBE 3 ALTAZ 9883 - Manual (Page 6)

replacing the EZ Finder ii Battery
Replacement 3-volt lithium batteries for the EZ Finder II are
available from many retail outlets. Remove the old battery by
inserting a small flat-head screwdriver into the slot on the bat-
tery casing (Figure 4) and gently prying open the case. Then
carefully pull back on the retaining clip and remove the old
battery. Do not overbend the retaining clip. Slide the new bat-
tery under the battery lead with the positive (+) side facing
down and replace the battery casing.
5. using Your telescope —
astronomical observing
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, when you look up at the sky with just your eyes, the stars
are twinkling noticeably, the seeing is bad and you will be lim-
ited to viewing with low powers (bad seeing affects images at
high powers more severely). Planetary observing may also be
poor.
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.
One good way to tell if conditions are good is by how many
stars you can see with your naked eye. If you cannot see stars
of magnitude 3.5 or dimmer then conditions are poor.
Magnitude is a measure of how bright a star is, the brighter a
star is, the lower its magnitude will be. A good star to remem-
ber for this is Megrez (mag. 3.4), which is the star in the “Big
Dipper” connecting the handle to the “dipper”. If you cannot
see Megrez, then you have fog, haze, clouds, smog, or other
conditions that are hindering your viewing. (See Figure 5)
tracking celestial objects
The Earth is constantly rotating about its polar axis, complet-
ing one full rotation every 24 hours; this is what defines a
“day”. We do not feel the Earth rotating, but we can still tell
that it is at night by seeing 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 updated over time to keep an object in the field of
view. When viewing the with the SpaceProbe 3 Altaz, you will
need to give the tube a light tug or push in azimuth as well as
an occasional turn of the altitude micro-motion thumbwheel to
keep the object in the field of view. (Make certain the azimuth
lock knob is slightly loosened before moving the scope in the
azimuth position.) Objects will appear to move faster at higher
magnifications, when the field of view is narrower. Remember
that objects are inverted in the telescope, so when you move
the telescope in one direction, the object in the eyepiece will
move in the opposite direction than you would normally expect.
This takes some getting used to, but becomes second nature
after a few nights out with the telescope.
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 cool to the temperature outdoors.
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.
Figure 5. Megrez connects the Big Dipper’s handle to it’s
“pan”. It is a good guide to how conditions are. If you can not
see Megrez (a 3.4 mag star) then conditions are poor.
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