Focusing The Telescope - Orion SpaceProbe II 76mm Instruction Manual

The maximum attainable magnification for a telescope is
directly related to how much light it can gather. The larger the
aperture, the more magnification is possible. In general, a fig-
ure of 50x per inch of aperture is the maximum attainable for
most telescopes. Going beyond that will yield simply blurry,
unsatisfactory views. Your SpaceProbe II 76mm reflector has
an aperture (primary mirror diameter) of 76mm, or 3.0 inches,
so the maximum magnification would be about 150x (3 x 50).
This level of magnification assumes you have ideal atmo-
Altitude lock knob
Figure 9.
Thread in the altitude lock knob.
spheric conditions for observing (which is seldom the case).
Keep in mind that as you increase magnification, the bright-
ness of the object viewed will decrease; this is an inherent
principle of the laws of physics and cannot be avoided. If mag-
nification is doubled, an image appears four times dimmer.
If magnification is tripled, image brightness is reduced by a
factor of nine!
So start by using the 25mm eyepiece, then try switching to the
10mm eyepiece later if you want to boost the magnification.

Focusing the Telescope

To focus the telescope, turn the focus wheels (see Figure 11)
forward or back until you see your target object (e.g., stars,
the Moon, etc.) in the eyepiece. Then make finer adjustments
until the image is sharp. If you're having trouble achieving ini-
tial focus, rack the focuser drawtube all the way in using the
focus wheels, then while looking into the eyepiece microly
turn the focus wheels so that the drawtube extends outward.
Keep going until you see your target object come into focus.
Note that when you change eyepieces you may have to adjust
the focus a bit to get a sharp image with the newly inserted
eyepiece.
What to Expect
So what will you see with your telescope? You should be able
to see bands on Jupiter, the rings of Saturn, craters on the
Moon, the waxing and waning phases of Venus, and many
bright deep-sky objects. Do not expect to see color in nebu-
las and galaxies as you do in astrophotographs, though. Our
eyes are not sensitive enough to see color in faint deep-sky
objects. But as you become more experienced and your
observing skills get sharper, you will be able to ferret out more
and more subtle details and structure from dim objects.
As mentioned previously (but it's worth repeating), the
SpaceProbe II 76mm reflector is not suitable for daytime ter-
restrial viewing because the image seen in the eyepiece will
be rotated – which is normal for reflector type telescopes. But
in space there is no right-side-up!)
Objects to Observe
Now that you are all set up and ready to go, what is there to
look at in the night sky?
A. The Moon
With its rocky surface, the Moon is one of the easiest and
most interesting objects to view with your telescope. Lunar
craters, maria, and even mountain ranges can all be clearly
seen from a distance of 238,000 miles away! With its ever-
changing phases, you'll get a new view of the Moon every
night. The best time to observe our one and only natural sat-
ellite is during a partial phase, that is, when the Moon is not
full. During partial phases, shadows are cast on the surface,
which reveal more detail, especially right along the border
between the dark and light portions of the disk (called the
"terminator"). A full Moon is too bright and devoid of surface
shadows to yield a pleasing view. Make sure to observe the
Finderscope base
Figure 10.
Insert the red dot finder scope's bracket foot into the
base near the focuser as shown.
Foot
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