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A-
Abs The apparent mag at a star wou it were obser a standard di 10
parsecs, or 32.6 li olut Sun e o
would just be visible lear m y .
Air isk The apparent size f a star's disk produced even by a perfect optical system. Since the s r
be focused perfec t of the ligh trate into , and 1
a system of surrounding rings.
Alt-Azimuth Mounting A telescope moun depe of the
Altitude and Azim
Alti In astronomy, the e of a celestial o s Angular Di above or below elestial
horizon.
Ape the diameter of a y len rger reate
telescope's light- ng power.
App A measure of the brightness of a other celestial t as perceived by rver on
Arc lar 60 of a
Arc A unit of angular /3,600 o
Ast
A small unoffici s in
Ast A small, rocky bo star.
Ast
doscientific belie planets exert an influence o
strology has nothing in common with astronomy
.
Ast
ance between the Earth and the t is equal to 149, 0 km., usually rounded off to
00,000 km.
Aur
of l en charged par rom the solar w
s into and exc oms and
a p upper atmosphe
Azi gular dista an object eastwa ng the horizon, red from due no tween
e astronomical meridian (the vertical line passing through th
r of the sky and the north and
and the ver containing th al body whose position is to
.
B -
Binar
Binary
(Double) ars ir m al att
s. If r mo ound
tip eved ly 50 rs be
or multiple system ndiv that tely
are called visual b lti tar , A
is actually our nearest example of a multiple star system, it consists of three stars
, two very similar
to our Sun and one dim, small, red star orbiting around one another.
C -
Celestial Equator The projection of the Earth's equator on to the celestial sphere. It divides the sky into two equal
hemispheres.
Celestial pole
The imaginary projection of Earth's rotational axis north or south pole onto the celestial sphere.
Celestial Sphere An imaginary sphere surrounding the Earth, concentric with the Earth's center.
Collimation
The act of putting a telescope's optics into perfect alignment.
D -
Declination
(DEC)
The angular distance of a celestial body north or south of the celestial equator. It may be said to
correspond to latitude on the surface of the Earth.
E -
Ecliptic The projection of the Earth's orbit on to the celestial sphere. It may also be defined as "the apparent
yearly path of the Sun against the stars".
Equatorial mount A telescope mounting in which the instrument is set upon an axis which is parallel to the axis of the
Earth; the angle of the axis must be equal to the observer's latitude.
F -
olute magnitude nitude th ld have if ved from stance of
ght-years.
The abs
on Earth on a c
e magnitude of the
oonless night awa
is 4.8. at a distanc
m surface light
f 10 parsecs, it
fro
y d o tar can neve
6 per cent into
tly, 84 per cen t will concen a single disk
ting using two in ndent rotation axis allowing movement instrument in
uth.
tude altitud bject is it stance the c
rture telescope's primar s or mirror; the la the aperture, the g r the
gatheri
arent Magnitude relative star or objec an obse
Earth.
minute A unit of angu
size equal to 1/ degree.
second size equal to 1 f a degree (or 1/60 of an arcminute).
erism
al grouping of star the night sky.
eroid
rology
dy that orbits a
f that the positions of stars and
The pseu
affairs; a
n human
ronomical unit
(AU)
The dist
Sun. I 597,90
150,0
ora
The emission
ules in
ight wh ticles f ind slam ites at
molec
muth The an
lanet's
nce of
re.
rds alo
measu rth, be
th e
cente
south points on the horizon) tical line e celesti
be measured.
y Stars
stars are pairs of
on Center
of Ma
st that, because of th
a group of three o
e utual gravitation
re stars revolve a
raction, orbit
one another, it
around a comm
is called a mul
s
le system. It is beli
r
percent of all sta
that approximate long to binary
s. Systems with i idual components can be seen separa by
a telescope
inaries or visual mu ples. The nearest "s " to our solar system lpha Centauri,
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