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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 rotation.
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 begins 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
magnifications 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
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