Apertura Dobsonian Telescope, Owner'S Manual

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ambient outside air temperature outside. Larger scopes take longer to equalize and
should be given half- to one-full hour depending on the temperature difference (one
hour for a difference of 40 degrees Fahrenheit). Keeping your telescope and optics in an
outside or non-environmentally controlled building such as a garage or shed can
decrease the time it takes for the temperature differential to stabilize. To aid in
equalizing the temperature of your Apertura™ Dobsonian Telescope, plug in the
onboard fan. The fan pulls in outside air to more quickly stabilize the internal
temperature of the scope, especially the large primary mirror.
Viewing Conditions
The quality of the conditions for viewing are referred to as “seeing,” usually rated on a
scale of 1 to 10, with 10 as perfect seeing and 1 as very poor. There are two major
conditions to notice in evaluating viewing conditions on any given night:
atmospheric
disturbance and air transparency . The best conditions for astronomical viewing are
when atmospheric disturbances are at a minimum. Lower your expectations when
trying to use your scope too early in the night or trying to focus on objects close to the
horizon as this will impair your ability to view clearly. Generally, you want to set your
telescope up on the highest point possible as it affords the highest quality viewing and
isn’t as subject to atmospheric disturbances. A good way to determine how well you will
be able to see on any given night is to look at bright stars about 40 degrees above the
horizon and look for twinkling of stars. Twinkling is caused by atmospheric disturbances
and is an indicator that quality viewing may be difficult. Though, often what twinkles
near the horizon will become steadier later in the evening as it moves higher in the night
sky.
Also affecting the viewing quality is the transparency (clarity) of the air. Remember that
our viewing of the universe from the ground begins by looking through many miles of air
that is full of particles and water which is in constant motion and changes regularly.
Tracking Celestial Objects
Since the Earth is always rotating, astronomical objects will appear to move across the
night sky. When using your Apertura™ Dobsonian Telescope for a little while, you need
to manually track the observed objects by carefully moving the scope’s tube to keep the