Bresser National Geographic 90-65000 Instrucciones De Uso página 9

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 magnification can also be increased. Also
see Eyepiece.
Focal width:
Everything that magnifies an object via an optic (lens) has a certain focal width. The
focal width is the length of the path the light travels from the surface of the lens 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.
Lens:
The lens 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).
Eyepiece:
An eyepiece is a viewing system comprised of one or more lenses. The eyepiece
magnifies the clear image generated at the focal point of a lens.
There is a simple formula for calculating magnification:
Focal width of the telescope tube / Focal width of the eyepiece
= Magnification
In a telescope, the magnification depends on both the focal width of the telescope
tube and the focal width of the eyepiece.
Magnification:
The magnification corresponds to the difference between observation with the naked
eye and observation through a magnification apparatus (e.g. a telescope). Observa-
tion with the naked eye is considered single, or 1x magnification. Accordingly, if a
telescope has a magnification of 30x, then an object viewed through the telescope
will appear 30 times larger than it would with the naked eye. Also see Eyepiece.
Useful accessories can be found at www.bresser.de
Possible objects for observation:
We have compiled and explained a number of very interesting celestial bodies and
star clusters for you. On the accompanying images at the end of the instruction
manual, you can see how objects will appear in good viewing conditions through your
telescope using the eyepieces that came with it.
The Moon
The moon is the Earth's only natural satellite.
Diameter: 3,476 km
Distance: approx. 384,400 km from Earth
The moon has been known to humans since prehistoric times. It is the second bright-
est object in the sky (after the sun). Because the moon circles the Earth once per
month, the angle between the Earth, the moon and the sun is constantly changing;
one sees this change in the phases of the moon. The time between two consecutive
new moon phases is about 29.5 days (709 hours).
Orion Nebula (M 42)
M 42 in the Orion constellation
Distance: 1,344 light years from Earth
With a distance of about 1,344 light years from the Earth, the Orion Nebula (Messier
42, abbreviation: M 42) is the brightest diffuse nebula in the sky. It is visible with the
naked eye and a rewarding object for telescopes in all sizes, from the smallest field
glass to the largest earthbound observatories and the Hubble Space Telescope.
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