Celestron FirstScope 60EQ Instruction Manual page 12

The right ascension setting circle does not move as the telescope moves in right ascension, and thus it must be
aligned each time you want to use it to find a new object. However, you don't need to use a bright star each time.
Instead, you can use the object you're observing at the time.
Now, using a star chart or atlas, you can find numerous objects. First, move the telescope in declination to the
correct declination coordinate. Then move the telescope in right ascension until the indicator points to the correct
coordinate.
After moving the telescope to the correct celestial coordinates, look through the lower power eyepiece to see if you
have located the object you wish to view. Center the object in eyepiece. If the object is not visible in the eyepiece,
gradually pan the telescope, using the right ascension and declination cables, until the object is visible.
M A G N I F I C A T I O N
M A G N I F I C A T I O N
The magnification (or power) of a telescope varies depending upon the focal length of the eyepiece being used and
the focal length of the telescope.
The Firstscope 60 telescope has a focal length of 900mm and comes with a 20mm 1¼" eyepiece. To calculate
magnification, use the following formula, in which FL = focal length:
FL (telescope) in mm
Magnification =
FL (eyepiece) in mm
Therefore, if you use the 20mm eyepiece your magnification is 900/20 = 45x. The same formula can be applied to
any of your eyepieces.
Celestron offers numerous optional eyepieces to expand your range of magnification. Eyepieces come in barrel
diameters of .96" and 1¼". In general, 1¼" eyepieces are of a higher optical quality and give you sharper images,
along with a wider field of view and better eye relief.
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 (with sharp images) is equal to 60 times the aperture of the telescope
(in inches). So, with a 80mm telescope it has a maximum useful power of 189x (3.15" x 60) and with the 70mm the
maximum is 165x (2.7559 x 60). Most of your viewing will be done in the range of 30x to 120x. Higher powers are
used mainly for lunar and sometimes planetary observing where you can greatly enlarge the image. The images at
extremely high powers like 675x magnify the image bur remember that the contrast will be very low and the image
somewhat blurred due to the super power. For the brightest images with the most contrast, use the lower powers
with a smaller image scale.
13