18
The moon
The moon is Earth's only natural satellite.
Diameter: 3,476 km / Distance: 384,400 km from Earth (average)
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).
Constellation Orion: The Orion Nebula (M 42)
Right Ascension: 05
h
35
m
(hours : minutes) / Declination: -05° 22' (Degrees : minutes)
Distance: 1,344 light years from Earth
Though it is more than 1,344 light years from Earth, the Orion Nebula (M 42) is the brightest diffuse
nebula in the sky. It is visible even with the naked eye and a worthwhile object for telescopes of all types
and sizes. The nebula consists of a gigantic cloud of hydrogen gas with a diameter of hundreds of light
years.
Constellation Lyra: The Ring Nebula (M 57)
Right Ascension: 18
h
53
m
(hours : minutes) / Declination: +33° 02'
(Degrees : minutes)
Distance: 2,412 light years from Earth
The famous Ring Nebula (M57) in the Lyra constellation 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 a gas structure in the form of a sphere or an
ellipse. If you were to look at the Ring Nebula from the side, it would look like the Dumbbell Nebula (M
27). When viewed from Earth, we are looking directly at the pole of the nebula.
Constellation Vulpecula (Little Fox):
The Dumbbell Nebula (M 27)
Right Ascension: 19
h
59
m
(hours : minutes) / Declination: +22° 43' (Degrees : minutes)
Distance: 1,360 light years from Earth
The Dumbbell Nebula (M 27) was the first planetary nebula ever discovered. On 12 July 1764, Charles
Messier discovered this new and fascinating class of objects. We see this object almost directly from its
equatorial plane. If we could see the Dumbbell Nebula from one of its poles, we would probably see the
shape of a ring, something very similar to what we know as the Ring Nebula (M 57). In reasonably good
weather, we can see this object well, even with low magnification.
Telescope ABC’s
What do the following terms mean?
Erecting lens (18):
The erecting lens is set into the eyepiece holder of the telescope before the eyepiece itself. This lens can
produce an additional magnification (mostly around 1.5 X) via the integrated lens in the eyepiece. The image
will be turned around if you use an erecting lens, but it appears upright and even properly oriented on the
vertical axis.
