Meade Instruments Polaris 80mm Instruction Manual download pdf (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

Monture

Diagonale

Miroir Diagonal

Image Focalisée

Miroir Primaire

Vis D'inclinaison

du Miroir Pr

imaire

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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Meade Instruments Polaris 80mm Instruction Manual Page 19

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