Celestron TABLETOP 76 31034 Manuel - Page 5

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Given the celestial coordinate system, it now becomes possible to find celestial objects by translating

their celestial coordinates using telescope pointing positions. For this you use setting circles (if you

have the Firstscope 76 EQ - equatorial mount models) for R.A. and Dec. to find celestial coordinates

for stellar objects which are given in star charts and reference books.

Finding Objects with the Altazimuth Mount

Loosen the clamp locks on the telescope mount (O and S), then move the telescope in the desired

direction.

Look through the finderscope and pan the telescope until the object appears in the field of view.

The object will quickly move out of the field of view and you will have to slowly keep moving the

telescope as the earth rotates on its axis.

5. MAGNIFICATION (POWER)

The magnification (or power) of a telescope is variable depending upon the focal length of the eyepiece

being used along with the focal length of the telescope.

A. Your telescope has a focal length of 600mm.

To calculate the magnification we use the following formula:

where FL(telescope) is the focal length of the telescope and FL(eyepiece) is the focal length of the

eyepiece. So, if you use a 20mm eyepiece your magnification is 600/20 = 30x.

There are numerous optional eyepieces that are available to expand your range of magnification. There

are various types of eyepieces of varying quality to choose from.

B. Magnification through the telescope has its limits. These limits are determined by the laws of optics

and the nature of the human eye. The maximum usable power is equal to 60 times the aperture of the

telescope (in inches). So your telescope has a maximum useful power of 180x (3" x 60). You can

create power higher than this limit but the images will be dark and blurred with poor contrast.

The maximum power is used only under ideal conditions which are not common. Most of your viewing

will be done in the range of 25x to 120x. Higher powers are used mainly for lunar and planetary

observing under ideal seeing conditions.

C. Your telescope also has supplied as standard equipment a 2x Barlow Lens - .96". The Barlow Lens

doubles the power of any eyepiece that you use.

FL telescope

(

Magnification

FL eyepiece

(

)