Bresser 114 - Cleaning Instructions; Telescope ABC

6
There is a simple formula for calculating the magnication:
Focal width of the telescope tube / Focal width of the eyepiece
= Magnication
The magnication also depends on the focal width of the telescope tube. The telescope has a focal length of
500 mm. From this formula, we see that if you use an eyepiece with a focal width of 20 mm, you will get the
following magnication:
500 mm / 20 mm = 25X magnication
The table below shows some common magnications.
Telescope tube
focal width
Focal width of eyepiece Magnication Magnication with
2X Barlow lens
500 mm 20 mm 25X 50X
500 mm 6 mm 83X 167X
NOTES on cleaning
• Clean the eyepieces and lenses only with a soft, lint-free cloth, like a microbre cloth. Do not apply excess
pressure to the cloth to avoid scratching the lenses.
• To remove more stubborn dirt, moisten the cleaning cloth with an eyeglass-cleaning solution, and wipe the
lenses gently.
• Protect the device from dust and moisture. After use, particularly in high humidity, let the device acclimatise
for a short period of time, so that the residual moisture can dissipate before storing. Remove the dust cover
and store it in the included bag during use.
• To remove dust on the mirrors, use a ne brush or air blower (from your local camera shop or optician). Don’t
touch any mirror surface with your ngers — they may damage the coating.
Telescope ABC:
What do the following terms mean?
Barlow Lens:
The Barlow lens was named after its inventor, Peter Barlow, a British mathematician and physicist who lived
from 1776–1862. The lens can be used to increase the focal width of a telescope. Depending on the type of
lens, it is possible to double or even to triple the focal width. As a result, the magnication can also be in-
creased. Also, see Eyepiece.
Focal width:
Everything that magnies an object via an optic (lens/mirror) has a certain focal width. The focal width is the
length of the path the light travels from the surface of the lens/mirror to its focal point. The focal point is also
referred to as the focus. In focus, the image is clear. In the case of a telescope, the focal widths of the telescope
tube and the eyepieces are combined.
Mirror:
The mirror bends the light which falls on it in such a way that the light creates a clear image at the focal point,
after it has traveled a certain distance (focal width).