1. Mapping the Celestial sphere
Some definitions
Locating stars and deep space objects
Describing an objects position

2. The Celestial Sphere

3. Some Definitions Celestial (Heavens)
Imaginary Points in space directly in line with the earth
Celestial sphere:
The canopy of stars resembling a painting in the night Sky
Celestial Poles:
Points where the earth’s axis intersects with the celestial sphere

4. Celestial North Pole
Polaris (North Star)

5. Celestial South Pole No Southern star
Southern pole: Use the southern cross:

6. Some Definitions Celestial Equator
Extend the earth's equator outward to the celestial sphere

7. Describing an objects position in the night sky with respect to the celestial Equator
Declination
(Latitude)
Right Ascension
(Longitude)

8. Location of a star Betelgeuse (470 light-years away; 20x > Sun)
RA: 5h 55m 10.2s east of vernal equinox
dec: 7°24’26” north of celestial equator

9. Some Definitions Zenith Nadir Horizons
Imaginary point on celestial sphere directly overhead (90°)
Nadir
Exact opposite of the Zenith (you can not see it)
Horizons
Place where the earth and sky appear to meet
Halfway between zenith and nadir

10. It cuts the celestial sphere into two halves
Some Definitions
Meridian
Imaginary north-south line on the celestial sphere that is directly overhead on the observer
It cuts the celestial sphere into two halves
Morning half (a.m.)
Evening half (p.m.)

11. Also known as alpha Canis Major (or aCMa)
Constellations
Every star and object in the celestial sphere is in a constellation
To locate a star
Specify a constellation
Rank it by order of brightness
Brightest star?
Sirius
Found in Canis Major
Also known as alpha Canis Major (or aCMa)

12. Putting the maps together

13. Not a constellation Asterisms
A small grouping of stars, that do not make a constellation
E.g.. The big dipper is part of Ursa Major

14. Location of nearest stars
Alpha Centauri,
Beta Centauri,
and Proxima Centauri
RA: 14h 29m 41s east of vernal equinox
dec: -62°40’46” south
Proxima Centauri
(4.2 l-y but too dim to see w/o telescope)
Alpha and Beta
(4.4 l-y; apparent magnitude of -.28 combined)

15. Changing Constellations
Throughout the seasons positions of constellation change do to earths revolution around the sun
Over long periods of time constellations can change
Star positions mover relative to each other on the celestial sphere