Transcript Astronomy 101

Astronomy 101
Whats up there?
Stellar Magnitude
Stars are graded by how bright they are
 The brightest stars are stars of the 1st
magnitude.
 The dimmest stars you can see (with just
your eyes) are stars of the 6th magnitude.
 A star of the 1st magnitude is 100x brighter
than a star of the 6th magnitude
 Thus a star of the 2nd magnitude is 2.512
dimmer than a 1st mag star.
Stellar Magnitude
0.03 Vega (chosen as the zero point)
-1.47 Sirius (brightest star in the sky)
-2.94 Maximum brightness of Jupiter
-3.82 Maximum brightness of Venus
-5.9 Brightness of ISS (space station)
-9.50 Iridium flare
-12.92 full moon
-26.74 Sun
Oh Be A Fine Girl Kiss Me
Class Temperature
Color
O
30,000 - 60,000 °K
Blue
B
10,000 - 30,000 °K
Blue
A
7,500 - 10,000 °K
White
F
6,000 - 7,500 °K
White (Yellow)
G
5,000 - 6,000 °K
Yellow
K
3,500 - 5,000 °K
Orange
M
2,000 - 3,500 °K
Red
What to look for?

Star clusters
Open clusters (M11)
 Globular clusters (M13)


Nebula
Planetary (M57)
 Dark (Horsehead Nebula)
 Emission nebula (M42)
 Supernova Remnant (M1)

What to Look for?
What to Look for?
Comets - Watch the web….
 Asteroids – Go to Minor Planet Center
 Satellites – http://heavens-above.com
 Planets

Inferior – Mercury, Venus
 Superior – Mars, Jupiter, Saturn
 Telescope – Everything else.

List of things to look for
Messier catalog – 110 objects List of
things that are not comets…
 Caldwell catalog – 109 objects (list made
by Patrick Moore)
 Herschel 400 catalog (400 of the 2000 or
so objects found by William Herschel)
 NGC catalog - ~7000 objects

Focal Ratio
The focal ratio is the
ratio of the light path
to the size of the
objective.
My telescope has a 8”
mirror, and a 50” light
path.
Thus the focal ratio is
F/6 (F6.25)
Magnification
The magnification of your telescope is the
focal length of your telescope divided by
the focal length of your eyepiece.
 My 8” F/6.25 has a focal length of 50” =
1270 mm
 My widest field eyepiece is a 32 mm.
 SO: This gives me a magnification of ~40.
 My 10mm eyepiece give me 127x.
 Using my 2.5 barlow lens I can get 317.5x

Field of view
Your dark adapted eye has a Pupil size of
4 to 9 mm
 Eyepieces are sold by size (25 mm) and
field of view (50 deg).
 Field of view is Eyepiece
FoV/Magnification
 Thus, for my telescope

50/(1270/25) = 1 degree