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Bresser 90-65000 National Geographic Manual

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EN
Focal width:
Everything that magnifi es 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 magnifi es the clear image gener-
ated at the focal point of a lens.
There is a simple formula for calculating magnifi cation:
Focal width of the telescope tube / Focal width of the eyepiece
= Magnifi cation
In a telescope, the magnifi cation depends on both the focal width of the telescope tube and the focal width of the
eyepiece.
Magnifi cation:
The magnifi cation corresponds to the difference between observation with the naked eye and observation through
a magnifi cation apparatus (e.g. a telescope). Observation with the naked eye is considered single, or 1x magnifi ca-
tion. Accordingly, if a telescope has a magnifi cation 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 brightest 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 fi eld glass to the largest earthbound observatories and the Hubble Space Telescope.
… 9 …


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