Bresser University of Oxford 114/500 Mode D'emploi page 7

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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). Observation 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 (Page 33), 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 of
all sizes, from the smallest field glass to the largest earthbound observatories and the Hubble Space Telescope.
When talking about Orion, we're actually referring to the main part of a much larger cloud of hydrogen gas and
dust, which spreads out over the half of the Orion constellation. The expanse of this enormous cloud stretches
several hundred light years.
Ring Nebula in Lyra constellation (M 57)
M 57 in the Lyra constellation
Distance: 2,412 light years from Earth
The famous Ring Nebula (M 57) in the constellation of Lyra is often viewed as the prototype of a planetary
nebula; it is one of the magnificent features of the Northern Hemisphere's summer sky. Recent studies have
shown that it is probably comprised of a ring (torus) of brightly shining material that surrounds the central star
(only visible with larger telescopes), and not of a gas structure in the form of a sphere or an ellipse.
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