Meade Infinity 102, Instruction Manual

HAVE A GOOD TIME, 

ASTRONOMY IS FUN!

SPECIFICATIONS
Infinity 80 model:

Objective lens diameter                80mm(3.2”)

Optical tube focal length                     400mm

Focal ratio                                                   f/5

Mounting type                               Alt-azimuth

Viewfinder                                          Red-dot

Infinity 90 model:

Objective lens diameter                90mm(3.5”)

Optical tube focal length                     600mm

Focal ratio                                                f/6.7

Mounting type                               Alt-azimuth

Viewfinder                                          Red-dot

Infinity 102 model:

Objective lens diameter              102mm(4.0”)

Optical tube focal length                     600mm

Focal ratio                                                f/5.9

Mounting type                               Alt-azimuth

Viewfinder                                          Red-dot

What do the specifications mean?

Optical tube focal length is the distance light 

travels in the telescope before being brought 

to focus in you eyepiece. Depending on the 

telescope model, the focal length is either 

400mm or 600mm long. Look at the specifi-

cation table to find out your telescopes focal 

length.
Objective lens diameter is how big the  

front lens is on your scope.  Telescopes are 

always described by how large their objec-

tive lens is.  Depending on your telescope 

model, the lens diameter is either 80mm, 90 

or 102mm.
Other telescopes are 50mm, 8 inches, 16 

inches, or even 3 feet in diameter.  The 

12

Hubble Space 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 shorter the exposure time is 

needed when a camera is hooked up to the 

telescope. For example, the Infinity 80 tele-

scope has fast focal ratio at f/5. Sometimes, 

astronomers use focal reducers to make 

slow exposure telescopes have faster focal 

ratios.
Alt-azimuth mounting simply means your 

telescope moves up and down (altitude  

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 CALCU-

LATE THE MAGNIFICATION OF YOUR 

EYEPIECE

The power of a telescope is how much it 

magnifies objects. For an Infinity 90, the 

26mm eyepiece magnifies an object 23.1 

Looking at or near the 

Sun

 will cause 

irreversible

 damage to your eye. Do not point this telescope at or near the Sun. Do not look through the telescope as it is moving.