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magazines.
HAVE A GOOD TIME,
ASTRONOMY IS FUN!
SPECIFICATIONS
Optical tube focal length 700mm
Objective lens diameter 70mm(2.8")
Focal ratio. . . . . . . . . . . . . . f/10
Mounting type. . . . . . . . . . . Altazimuth
What do the specifications mean?
Optical tube focal length is simply a
measurement of the length of the optical
tube. In other words, this is the distance
light travels in the telescope before being
brought to focus in you eyepiece. Your tube
is 700mm long.
Objective lens diameter is how big the
lens is on your scope. Telescopes are
always described by how large their
objective lens is. Your telescope is 70mm
or 2.8 inches. Other telescopes are 90mm,
8 inches, 16 inches, or even 3 feet in
diameter. The Hubble Telescope’s objective
lens has a diameter of 2.4 meters (that’s
7.8 feet across!).
The focal ratio helps determine how fast the
photographic speed of a telescope is. The
lower the focal ratio number, the faster the
exposure. f/5 is faster than f/10. The faster
the ratio, the faster exposure time is needed
when a camera is hooked up to the
telescope. Your telescope has slower focal
ratio at f/10. Sometimes, astronomers use
focal reducers to make slow exposure
telescopes have faster focal ratios.
Altaz mounting simply means your
telescope moves up and down (altitude
12
or “alt”), and side to side, (azimuth or “az”).
Other mounting configurations are
available for other telescopes, such as
equatorial mounting.
USE THE SPECIFICATIONS TO CALCULATE
THE MAGNIFICATION OF YOUR EYEPIECE
The power of a telescope is how much it
magnifies objects. Your 25mm eyepiece
magnifies an object 28 times. Your 9mm
eyepiece magnifies objects 78 times.
But if you obtain other eyepieces, you can
calculate how much magnification they have
with your telescope. Just divide the focal
length of the telescope by the focal length of
the eyepiece.
Focal Length of the Telescope
÷
Focal Length of the Eyepiece
=
Magnification
Look at the specifications. You will see that
the focal length of your scope is 700mm.
Looking at or near the Sunwill cause irreversibledamage to your eye. Do not point this telescope at or near the Sun. Do not look through the telescope as it is moving.
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