Meade Polaris 130mm User Manual - Page 19

POLARIS 127 Optical tube design Reflector Fig. 11 how fast the photographic speed of a telescope is. The lower the focal ratio number, the faster the 17 Optical tube focal length 1000mm exposure. F/5 is faster than f/10. Monture Primary mirror diameter 127mm (5.0") Diagonale Miroir Diagonal Miroir Primaire The slower the focal ratio, the longer the exposure time is needed when a Focal ratio f/7.9 camera is hooked up to the telescope. Mount Large German Equatorial Image Focalisée For Vis D'inclinaison du Miroir Primaire example, the Polaris 90 Refractor has slow focal ratio at f/10. Sometimes, POLARIS 130 The Newtonian Reflecting Telescope astronomers use focal reducers to make slow exposure telescopes have Optical tube design Reflector Primary mirror diameter (reflectors) or faster focal ratios. Optical tube focal length 650mm Objective lens diameter (refractors) big the mirror or lens is on your is how scope. Primary mirror diameter 130mm (5.1") Telescopes are always described by how Focal ratio f/5 large their primary mirror/lens is. Mount Large German Equatorial For example, the objective lens on the Polaris 90 is 90mm or USE THE SPECIFICATIONS Fig. 12 TO CALCULATE MAGNIFICATION OF THE YOUR EYEPIECE 3.5 inches. Telescopes come in The power of a telescope is how What do the specifications mean? many different sizes. They can be 70mm, 8 inches, 16 inches, Optical tube focal length is simply a measurement or even 3 feet in diameter. The much it magnifies objects. Each telescope has its own set of focal l1engths and, therefore, different of the length of the optical tube. In other words, Hubble Space Telescope's 2 magnifications when used with this is the distance light travels in the telescope primary mirror has a diameter various eyepieces. For example, before being brought to focus in you eyepiece. of 2.4 meters (that's 7.8 feet the Polaris 90 used 3with the 25mm For example, the Polaris 90 Refractor tube is across!). 900mm long. The focal ratio helps determine Secondary Mirror Assembly eyepiece magnifies an object 36 times. The 9mm eyepiece used with the Polaris 90 will magnify 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.