the presentation is about Field Astronomy, generally deals with astronomical terms & Co-ordinate system related to field astronomy. Astronomical terms like celestial sphere, Zenith, Nadir & Celestial pole/ equators all are included in these slides; rather than that Celestial latitude & longitude co-ordinate system, Altitude & azimuth co-ordinate system, declination & Right ascension co-ordinate system & Declination & hour angle co-ordinate system are explained in these slides.

2. Astronomy
the science which deals
with heavenly body
Celestial sphere
A sphere of infinite
radius with the earth at
centre.
INTRODUCTION

3. Zenith
Point immediately above the
observation station
Nadir
Point immediately vertically below
the observation station
Celestial Poles
Points where earth’s axis of rotation
meet with celestial sphere
Celestial equator
Great circle right angle to the axis of
rotation
TERMS RELATED TO CELESTIAL
SPHERE

4. Co-ordinate Systems
The Celestial Latitude & Longitude
system
The Horizon System (Altitude & Azimuth)
The Independent Equatorial System
(Declination & Right Ascension System)
The Dependent Equatorial System
(Declination & Hour angle system)

5. Longitude & Latitude
Latitude
Angle between the direction of
a plumb line & plane of
equator
Co-latitude
The complement of the latitude
(90 degree – latitude)
Longitude
Angle between a fixed
reference meridian (Greenwich)
& meridian of the place.

6. The Horizon System
(Altitude and Azimuth System)
Vertical circle
The great circle passing through the zenith &
nadir
Observer’s meridian
The great circle passes through zenith &
Nadir as well as through the poles.
Altitude
The angular distance above the horizon,
measured on the vertical circle
Co-altitude & Zenith Distance
The complement of the altitude
Azimuth
Angle between the observer’s meridian &
the vertical circle passing through the body

7. The Independent equatorial System
(Declination & Right Ascension System)
Declination
Analogous to latitude & is measured in
degrees north or south of the celestial
equator
Vernal Equinox or First Point of Aries
Point on the celestial equator where
sun crosses the equator
Right Ascension
Analogous to the longitude & is
measured eastward along the celestial
equator from the vernal equinox to its
intersection with the objects hour
circle

8. The Dependent Equatorial System
(Declination & Hour angle system)
Hour Circle
Great circles passing
through the north & south
celestial pole
Hour Angle
Angle between the
observer’s meridian &
declination circle
always measured in
westward direction.

9. Summary
Co-ordinate system

10. Summary
Co-ordinate system (CONTD.)
 Right Ascension is measured east of the vernal equinox in
hours, minutes, and seconds of time (0 to 24 hr).
Declination is measured north or south (+/–) of the celestial
equator in degrees, minutes and seconds of arc (–90o to +90o).
Longitude is measured east or west of Greenwich, England in
degrees, minutes and seconds of arc (180o W to 180o E).
Latitude is measured north or south (+/–) of the Earth's
equator in degrees, minutes and seconds of arc (–90o to +90o).
Azimuth is measured east of the northern horizon, or your
meridian, in degrees, minutes and seconds of arc (0o to 360o).
Elevation is measured up from the horizon in degrees,
minutes and seconds of arc (0o to 90o)

11. Any Question?