9
Note that the setting circles may be a little hard to rotate.
But just grab it firmly around the edge and twist it and it
will rotate.
Finding Objects with the Setting Circles
Now that both setting circles are calibrated, look up the coordi-
nates of an object you wish to view.
1. Loosen the R.A. lock knob and rotate the telescope until
the R.A. value from the star atlas matches the reading on
the R.A. setting circle. Remember to use the lower set of
numbers on the R.A. setting circle if you’re in the Northern
hemisphere. Retighten the lock knob.
2. Loosen the Dec. lock knob and rotate the telescope until the
Dec. value from the star atlas matches the reading on the
Dec. setting circle. Remember that values of the Dec. setting
circle are positive when the telescope is pointing north of the
celestial equator (Dec. = 0°), and negative when the tele-
scope is pointing south of the celestial equator. Retighten
the lock knob.
Most setting circles are not accurate enough to put an object
dead-center in the telescope’s eyepiece, but they should place
the object somewhere within or near the field of view of the
finder scope, assuming the equatorial mount is accurately polar
aligned. Use the slow-motion controls to center the object in the
finder scope, and it should appear in the telescope’s field of view.
The R.A. setting circle must be re-calibrated every time you wish
to locate a new object. Do so by calibrating the setting circle for
the centered object before moving on to the next one.
Choosing an Observing Site
When selecting a location for observing, get as far away as
possible from direct artificial light such as streetlights, 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
Figure 14.
To find Polaris in the night sky, look north and find the
Big Dipper. Extend an imaginary line from the two "Pointer Stars" in
the bowl of the Big Dipper. Go about five times the distance between
those stars and you'll reach Polaris, which lies within 1° of the north
celestial pole (NCP).
Big Dipper
(in Ursa Major)
Little Dipper
(in Ursa Minor)
Cassiopeia
N.C.P.
Pointer
Stars
Polaris
Figure 15.
Loosen the latitude lock knob, then use the two
latitude adjustment T-bolts to set the latitude scale pointer to your
location’s latitude.
Figure 16.
The R.A. and Dec. setting circles allow you to locate
objects by their R.A. and Dec. coordinates.
Latitude scale
Pointer
RA setting
circle
Pointer
Dec. setting
circle
Mount attachment knob
Latitude lock
knob
Latitude
adjustment
T-bolts
