[10] The wonderful Cocoon Nebula lies in
the northern regions of Cygnus, the Swan.
This object consists of a cluster of stars
known as IC 5146 and a region which
exhibits both emission and reflection
characteristics known as Sharpless 2-125
(Sh2-125). Wide field shots of the nebula
show it sitting at the end of a long finger
of darkness caused by gas and dust
blocking the background stars of the Milky
Way Galaxy.
[11] A long exposure of the Pleiades
cluster (Messier 45) reveals a delicate
reflection nebula – galactic dust
illuminated by the light of the cluster
stars. (Ian Sharp)
[12] Glowing gas and clusters make up
the region of sky known as Orion's Sword.
At the top lies a beautiful reflection nebula
known as NGC 1977. Dark lanes of dust
crossing the nebula give the appearance
of a running figure and the nebula is
known informally as the "Running Man
Nebula". Below NGC 1977 lies the bright
gas cloud known as the Orion Nebula or
M42. The comma shaped region to the
upper-left of the brightest part of the
nebula is classified separately from the
main nebula and is known as M43. Finally,
the sword tip is defined by a small open
cluster below M42 known as NGC 1980.10is equivalent to latitude on the surface of the Earth. Right Ascension
requires a little more explaining, but corresponds more or less to celestial
longitude. Once these coordinates are known, if you are using a Go To
telescope, it is merely a question of punching in the coordinates and
letting the telescope do the rest. If you don’t use Go To, the objects are
best located by finding them on a chart and star hopping to their location.
Observations with the naked eye are very satisfying but today many
astronomers rely on photography.Photographing the Stars
Photographing the stars, clusters, nebulae and other galactic wonders
that exist within our own galaxy is something that can be undertaken with
quite modest equipment. At its simplest, setting a camera on a tripod and
pointing it up to the night sky with the shutter open for several minutes
should record the stars as trails. The motion that causes this isn’t anything
to do with the stars at all of course, but rather by the fact that the Earth on
which you and your camera are standing, is rotating underneath them.
All of the stars and constellations appear to rotate around two points in
the sky known as the celestial poles: the locations in the sky which sit
directly above the Earth's rotational poles. In the northern hemisphere,
the north celestial pole is almost marked by the star Polaris. In the
Southern Hemisphere the closest naked star to its celestial pole is the
rather dim Sigma Octantis. Sigma lies over a degree (two apparent full
Moon diameters) away from the actual pole and is at the limit of naked
eye visibility.
If you point a fixed camera at one of the celestial poles and take an extended
shot of the stars, they will trail around the pole, tracing out arcs of circles. If you
could expose the shot for a whole day, the arcs would eventually join up and
create complete circles.Hemisphere has the best examples with objects such as Omega Centauri
and 47 Tucanae almost literally having the ability to take your breath away
when viewed through a telescope.Cataloguing the Universe
There are many catalogues of these objects in existence. One of the most
famous is the Messier Catalogue, compiled by the French astronomer,
Charles Messier in 1771. The list was compiled to aid Messier in his hunt
for comets, creating a list of objects which he didn’t want to keep tripping
over. Today the 110 objects which now reside in the slightly extended
original catalogue, form essential viewing for amateurs the world over
with objects such as Messier 45, the Pleiades, and Messier 42, the Orion
Nebula. The entries are normally simply listed with an M prefix.
The Messier catalogue is biased towards the Northern Hemisphere
although many of its objects can be seen from the Southern Hemisphere
too. Patrick created his own list which he called the Caldwell Catalogue. In
truth this wasn’t meant to be taken seriously but has stuck. The Caldwell
Catalogue balances the hemispheres somewhat by starting in the far
north with C1, an ancient open cluster in the constellation of Cepheus, and
progressively moving further south with each new entry. The last entry,
C109 is a planetary nebula in the southern constellation of Chamaeleon,
located roughly 9° from the South Celestial Pole.
The more extensive New General Catalogue (NGC) contains 7,840
objects boosted by two further Index Catalogues (IC) adding an additional
5,386 objects.
The catalogues provide information about the object’s appearance
and position in the night sky. Positions are given by a coordinate system
known as Right Ascension and Declination (RA & Dec.). Declination
indicates the angular distance of the star from the celestial equator andAstronomer Book