15
Instruction manual
Starscopes on azimuthal mount
To view the image captured by the telescope,
you need the eyepieces. The telescope
collects and focuses the light and creates an
image that you view with an eyepiece. The
focal length of the eyepiece determines the
magnification factor. The lower the mag-
nification, the larger the visible area (field
of view).The higher the magnification, the
smaller the field of view and the brightness
of the image decreases. Therefore, there is
a „useful magnification“ for each telescope.
The possible magnification also depends on
the so-called „seeing“ (air turbulence) as well
as the transparency of the atmosphere (haze
etc.).
The highest magnification can only be achie-
ved on particularly clear nights with very
calm, clear air. In addition to the eyepiece,
there are magnification lenses (barlow lenses)
which double the magnification value of the
eyepiece, for example. A 2x Barlow lens thus
turns a 12.5 mm eyepiece into a 6.25 mm
eyepiece. The focal length is halved and the
magnification is doubled!
It is not always advisable to use a Barlow
lens, especially with high magnification
eyepieces (e.g. 4 mm), because there is not
enough collected light for this magnification
in small telescopes. The image becomes very
dark.
If you also want to observe nature with your
new telescope, you will quickly notice that
the image is mirrored vertically and/or hori-
zontally, unlike the image of binoculars.
This is not a problem when observing the
sky at night, but an upright and laterally
correct image is an advantage when obser-
ving nature. To achieve such an image, there
are - depending on the type of telescope -
so-called erect lenses or amici prisms. The
upright lenses usually provide magnification
at the same time. These optical elements are
always inserted between the focuser and the
eyepiece. If your complete package does not
include these parts, you can order them in
our online store.
Using accessories on the eyepiece side
The magnification in a telescope is calculated
by dividing the focal length of the telescope
by the focal length of the eyepiece.
Example:
Telescope focal length 700 mm
Eyepiece focal length 12.5 mm
700/12.5 = 56x magnification
This means that the smaller the eyepiece
focal length, the higher the magnification.
With a 2x Barlow lens, the magnification dou-
bles, in the example to 112x.
Examples for a telescope with 700 mm
Focal length (eyepiece focal length/magnifica-
tion/magnification with 2x Barlow lens ):
20 mm 35 x 70 x
12.5 mm 56 x 112 x
4 mm 175 x 350 x
Useful magnifications and calculation formulas
f.l.: Eyepieces • Barlow lens • Erect lens
