18
Examples of the telescope moved in R.A. and Dec
Fig.o
Telescope pointing South
Fig.p
1.
2.
Pointing to directions other than due North
Pointing in any direction other than due North
requires a combination of R.A. and Dec
positions (Fig.o). This can be visualized as a
series of Dec arcs, each resulting from the
position of rotation of the R.A. axis. In practice
however, the telescope is usually pointed, with
the aid of a finderscope, by loosening both the
R.A. and Dec locks and swivelling the mount
around both axes until the object is centred in
the eyepiece field. The swivelling is best done
by placing one hand on the optical tube and the
other on the counter-weight bar, so that the
movement around both axes is smooth, and no
extra lateral force is applied to the axis-
bearings. When the object is centred, make
sure the R.A and Dec locks are both re-
tightened to hold the object in the field and
allow tracking by adjusting only in R.A.
Pointing at an object
Pointing at an object, for example to the South
(Fig.p), can often be achieved with the optical
tube positioned on either side of the mount.
When there is a choice of sides, particularly
when there could be a long observing period,
the East side (Fig.p2) should be chosen in the
Northern Hemisphere because tracking in R.A.
will move it away from the mount's legs. This is
particularly important when using an R.A motor,
because if the optical tube jambs against the
mount's legs, it can result in damage to the
motor and/or the gears.
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