SKY-WATCHER S11670 User Manual page 30

agnifying Power
The amount by which a system increases the
apparent size of objects. Magnification is determined
by dividing the Focal Length of the telescope by the
Focal Length of the eyepiece.
Mirror
In a telescope, it is a highly polished surface made
to reflect light. Primary mirrors are usually made
spherical or paraboloidal (parabolic) to focus the
light rays.
bjective
The primary or largest element in an optical system;
sometimes called the "fixed optics."
Optical Tube Assembly
The housing and optical train of a telescope; not
including the mount,
accessories.
arabolic Mirror
A parabolic or more accurately a "paraboloidal"
mirror, is ground to a shape which brings all
incoming light rays to a perfect focus, on axis.
Polar Axis
A telescope mount's axis that is parallel with the
earth's axis. With a drive motor, the motion of stars
due to the earth's movement can be counteracted so
that they remain in the field.
Power
See Magnifying Power.
Prime Focus
The focal point of the objective mirror or lens.
esolution
The ability of an optical system to reveal details.
Resolving Power
The ability of a telescope to separate closely
positioned points.
Right Ascension
Similar to but not the same as Latitude on the
Earth's surface. It is the position eastwards from the
Vernal Equinox, in 24 one-hour units. The hours can
be sub-divided into minutes and seconds.
30
diagonal, eyepiece or
etting Circles
Circular scales attached to the telescope. They are
marked off in degrees of Declination and hours of
Right Ascension. Together, the circles allow the
position of a known object to be found by setting the
dials to the equatorial coordinates.
rue Field of View
How much sky, in angular measure, is available at
the eyepiece. It is contrasted with Apparent Field of
View, which measures the field of the eyepiece
alone.
ide Angle Eyepiece
An eyepiece with an Apparent field of view of more
than 50 degrees.
oom Eyepiece
An optical system which provides a variable focal
length.