Celestron 31041 Manuel d'instruction - Page 11

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then in the telescope. Now, rotate the right ascension circle to match the coordinates of the star with
the indicator mark.
4.
The right ascension setting circle does not move as the telescope moves in right ascension and thus it
must by aligned each time you want to use it to find a new object. However, you do not need to use a
bright star each time but you can use the object you are currently observing.
5.
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.
6.
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.
5
.
M
A
G
N
I
F
I
C
5
.
M
A
G
N
I
F
I
C
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. If you purchased one of the 76mm diameter models, your telescope has a focal length of 700mm.
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 10mm eyepiece your magnification is 700/10 = 70x.
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). For example, if you purchased the 114mm model (4.5") then your maximum
useful power is 270x (4.5" 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.
A
T
I
O
N
(
P
O
W
A
T
I
O
N
(
P
O
W
Magnification
11
E
R
)
E
R
)
FL telescope
(
)
=
FL eyepiece
(
)