HOW TO USE THE TELESCOPE MOUNT
Several techniques can be used to find objects in the sky:
Visual Pointing is the technique used by all beginners-simply move the
telescope to point at the target (usually a planet or Moon or bright star)
and look through the finder to center the object, followed by looking
through the eyepiece.
Star-hopping is a technique used by more advanced beginners and everyone
else, all the way up to the most experienced observers. This entails finding
a relatively bright star near the target then matching the view seen through
the finder with a star chart or finder chart to get close to where the
object should be. This technique is easiest with the Alt-Az mount, but
can be successfully employed by the EQ mount as well.
Offsetting is an additional technique that the EQ-mounted telescope can
employ. With this method, a star near to the target is chosen, and the
mount is offset north or south to a line that allows the telescope to
be moved east or west to find the object. This technique can be easily
matched with the field of view of a low-power eyepiece or the setting
circles on the mount can be used. Either way, it is the easiest way to
find objects for the EQ mount owner.
on the EQ mount can be used to find an object directly. Every object in
the sky has a pair of coordinates describing its position on the Celestial
Sphere. Those coordinates are its N-S position (called DEC, or Declination),
and its East-West coordinates (called RA, or Right Ascension). As on the
surface of the Earth, a position south of the Celestial Equator is preceded
by a minus sign, and all positions E-W are described by the number of
hours east of a North-South line called the Vernal Equinox (where the
sun is in the Sky on the first day of Spring), so this position goes from
0hr0min0sec to 23hr59min59sec.
The Celestial Coordinate System
The setting circles on the mount allow the telescope to be pointed directly
at a particular sky coordinate so long as the Polar Axis is coincident
with the axis of the Earth, and the Polar Axis setting circle is slipped
into the correct position for the current time. Every object directly
crossing the line that runs north and south, which passes directly overhead,
called the Meridian, will do so at a different time of the night. Yet,
each object has a discrete E-W coordinate, called its RA (Right Ascension).
Hence, the RA of a point on the meridian is always changing. Another way
to look at it is that a particular RA is always moving west. In order
to use the RA setting circle on your mount, it is first necessary to slip
the setting circle to read the correct RA for where the telescope is pointed.
This is easily done by centering a bright star and moving the setting
circle until it reads the correct coordinates for that star. After that¡¯s
done, to find an object, simply move the telescope until the coordinates
on both setting circles match the position of the object. This is the
way all professionals found objects prior to the advent of computers.
Computerized mounts are typically lined up on 2 or 3 selected stars,
after which the position of every object in the Celestial Sphere is internally
calculated. This type of mount keeps track of the passage of time, so
it knows where the object is in the sky, regardless of the time of night.
Finding an object is as simple as telling the telescope to find a particular
object or coordinates and pressing GoTo. It can't get much easier than