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Dec. lock lever
Dec. setting circle
Front opening
Azimuth adjustment knobs (2)
3a). Back the lock ring off by a few turns, for now. Refocus the
finder scope on a distant object by threading the objective
lens cell in or out of the finderscope body. Precise focusing will
be achieved by focusing the finder scope on a bright star.
Once the image appears sharp, retighten the locking ring
behind the objective lens cell. The finder scope's focus should
not need to be adjusted again.
Magnification & Eyepieces
Magnification, or power, is determined by the focal length of
the telescope and the focal length of the eyepiece. Therefore,
by using eyepieces of different focal lengths, the resultant
magnification can be varied.
Magnification is calculated as follows:
Telescope Focal Length (mm)
Eyepiece Focal Length (mm)
The Atlas 10 EQ has a focal length of 1200mm, which when
used with the supplied 25mm eyepiece yields a magnification of:
1000mm
25mm
The magnification provided by the 10mm eyepiece is:
1000mm
10mm
The maximum attainable magnification for a telescope is direct-
ly related to how much light it can gather. The larger the aper-
ture, the more magnification is possible. In general a figure of
60x per inch of aperture is the maximum attainable for most tel-
escopes. Your Atlas 8 EQ has an aperture of 8 inches, so the
maximum magnification would be about 480x. This level of
magnification assumes you have ideal conditions for viewing.
Keep in mind that as you increase magnification, the brightness
of the object viewed will decrease; this is an inherent principle
of the laws of physics and cannot be avoided. If magnification is
doubled, an image appears four times dimmer. If magnification
is tripled, image brightness is reduced by a factor of nine!
Figure 7.
= Magnification
= 40x
= 100x
The Atlas EQ Mount.
Always start with your lowest power eyepiece and work your
way up. Start by centering the object being viewed in the
25mm eyepiece. Then you may want to increase the magnifi-
cation to get a closer view. If the object is off-center (i.e., it is
near the edge of the field of view) you will lose it when you
increase magnification since the field of view will be narrower
with the higher-powered eyepiece. To change eyepieces, first
loosen the securing thumbscrew on the focuser's 1.25"
adapter. Then carefully lift the eyepiece out of the holder. Do
not tug or pull the eyepiece to the sides, as this will knock the
telescope off its target. Replace the eyepiece with the new
one by sliding it gently into the holder. Re-tighten the thumb-
screw, and refocus for your new magnification.
Using 2" eyepieces
The Atlas 8 EQ's focuser is capable of accepting optional 2"
eyepieces. To use 2" eyepieces you must remove the 1.25"
adapter from the focuser by loosening the two thumbscrews
that hold it in place (Figure 4). Once this adapter is removed,
insert a 2" eyepiece into the focuser and use the same thumb-
screws to secure the larger eyepiece.
6. Setting Up and Using the
Equatorial Mount
When you look at the night sky, you no doubt have noticed
that the stars appear to move slowly from east to west over
time. That apparent motion is caused by the Earth's rotation
(from west to east). An equatorial mount (Figure 7) is
designed to compensate for that motion, allowing you to easi-
ly "track" the movement of astronomical objects, thereby keep-
ing them from drifting out of your telescope's field of view
while you're observing.
This is accomplished by slowly rotating the telescope on its
right ascension (R.A.) axis, using the built in motor drive. But
first the R.A. axis of the mount must be aligned with the Earth's
rotational (polar) axis—a process called polar alignment.
R.A. setting circle
R.A. lock lever
Polar axis finder
scope
Latitude scale
Latitude
adjustment L-bolts
7
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