P
ointing your telescope
11
U
sing the Camera Adapter Tube
Fig.m
Rotate in Azimuth
(90°)
(180°)
S
E
(270°)
W
Zenith
Nadir
Meridian
Line
Tilt in
Altitude
Nadir
(0°/360°)
N
Camera Adapter
Tube
T-adapter
Camera
Focuser
Eyepiece
Holder
Fig.l
When you connect a camera directly to your telescope for "prime focus" photography, you sometimes require an
adapter so that the camera can be focussed. Some reflectors need more length than the focuser can travel, in order to
focus the camera, and some refractors are designed to be used with diagonals, so when used with only a camera,
their focal length has to be extended. This is particularly true when photographing near objects. Your camera with its
telescope "lens" may focus on a distant object such as a star, but will require the 2.5" camera adapter tube to focus on
a near object such as a bird.
The camera adapter tube is easily installed by
screwing it onto the T-threads of the eyepiece
holder, then screwing the specific T-adapter ring for
your camera (optional) onto the T-threads on the
other end of the camera adapter tube (Fig.l). This
makes the telescope into a "lens" which you then
attach to your camera as you would any other lens.
Pointing an altitude-azimuth (alt-az) mounted telescope is relatively easy. With the mount level, you can swivel
the telescope around on a plane parallel to your horizon and then tilt it up and down from there (Fig.c). You can
think of it as turning your telescope in azimuth until it is facing the horizon below a celestial object and then
tilting it up to the object's altitude. However, the Earth rotates and therefore the stars are constantly moving, so to
track with this mount you need to constantly nudge the optical tube in both azimuth and altitude to keep the
object in the field.
In reference material for your local position, the altitude will be listed as ±degrees (minutes, seconds) above or
below your horizon. Azimuth may be listed by the cardinal compass points such as N, SW, ENE, etc., but it is usually
listed in 360 degree (minutes, seconds) steps clockwise from North (0°), with East, South and West being 90°, 180°
and 270 °, respectively (Fig.m).
