Meade Instruments Polaris Series - Manual (Page 19)

POLARIS 127
Optical tube design……..................….Reflector
Optical tube focal length…..................1000mm
Primary mirror diameter…............127mm (5.0”)
Focal ratio…………...................…….....….f/7.9
Mount…….............…Large German Equatorial
POLARIS 130
Optical tube design……..................….Reflector
Optical tube focal length..........................650mm
Primary mirror diameter…..............130mm (5.1”)
Focal ratio…………….............................…….f/5
Mount…………........…Large German Equatorial
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.
For example, the Polaris 90 Refractor tube is
900mm long.
Primary mirror diameter (reflectors) or
Objective lens diameter (refractors) is how
big the mirror or lens is on your scope.
Telescopes are always described by how
large their primary mirror/lens is.
For example, the objective lens
on the Polaris 90 is 90mm or
3.5 inches. Telescopes come in
many different sizes. They can
be 70mm, 8 inches, 16 inches,
or even 3 feet in diameter. The
Hubble Space Telescope’s
primary mirror 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 slower the focal ratio, the longer
the exposure time is needed when a
camera is hooked up to the telescope.
For example, the Polaris 90 Refractor
has slow focal ratio at f/10. Sometimes,
astronomers use focal reducers to
make slow exposure telescopes have
faster focal ratios.
USE THE SPECIFICATIONS
TO CALCULATE THE
MAGNIFICATION OF YOUR
EYEPIECE
The power of a telescope is how
much it magnifies objects. Each
telescope has its own set of focal
lengths and, therefore, different
magnifications when used with
various eyepieces. For example,
the Polaris 90 used with the 25mm
eyepiece magnifies an object 36
times. The 9mm eyepiece used
with the Polaris 90 will magnify
2
1
3
Monture
Diagonale
Miroir Diagonal
Image Focalisée
Miroir Primaire
Vis D'inclinaison
du Miroir Primaire
Secondary Mirror Assembly
The Newtonian Reflecting Telescope
Looking at or near the Sun will cause irreversable damage to your eye. Do not point this telescope at or near the Sun. Do not look through the telescope as it is moving.
Fig. 11
Fig. 12
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