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TRACKING CELESTIAL OBJECTS
The Earth is always rotating about its polar axis, completing one full
rotation every 24 hours. This is what defines our “day”, and we see
it in the apparent movement of sun and stars throughout each rota-
tion. In the same way that the sun rises and sets each day, the stars
in the sky rise and set each night. The motion translates to a rate of
approximately .25° per minute, or 15 arc-seconds per second. This
is commonly referred to as the sidereal rate.
As you observe any celestial object, remember that it is in motion.
You will need to continuously update your telescope’s position
throughout a viewing session, which is where your Dobsonian’s fine
altitude and azimuth adjustments become useful. As an object be-
gins to leave your field of view, gently nudge the OTA in the correct
direction and bring it back to center.
Remember, the higher the magnification at which you’re viewing, the
smaller your field of view. Objects will appear to move faster as you
raise magnification, and more frequent positional adjustments will
need to be made.
SELECTING AN EYEPIECE
By using eyepieces of different focal lengths, many different magni-
fications can be achieved with your Zhumell Dobsonian telescope.
The best place to start is with the included 9mm and 32mm Plossl
eyepieces for higher and lower magnifications, respectively. Many
astronomers own a large number of eyepieces in order to customize
their equipment based on the object being viewed. To calculate the
magnification of a telescope/eyepiece combination, divide the focal
length of the telescope by the focal length of the eyepiece.
OBSERVATION TIPS FOR YOUR
ZHUMELL DOBSONIAN TELESCOPE
