Lab note 1
♦Definition of Zenith Angle and sun angle:
Zenith angle: the angle between the sun and the vertical, it could be over 90°.
Sun angle (altitude angle): angle of sun of the sun above the horizon, it is negative when the
sun drops below the horizon.
♦Calculation of Zenith Angle and Noon Sun Angle
In the case of location and declination are both in the same hemisphere:
If Latitude>Declination
Zenith Angle=Latitude-Declination
Noon Sun Angle=90°-Zenith Angle
If Latitude<Declination
Zenith Angle= Declination-Latitude
Noon Sun Angle=90°-Zenith Angle
In the case of location and declination are in different hemisphere:
Zenith Angle=Latitude+Declination
Noon Sun Angle=90°-Zenith Angle
♦Value of Declination
23.5°N (June Solstice)
Declination= 23.5°S (December Solstice)
0° (March/September Equinox)
♦Interpolation: a method of estimating the value at intermediate points according to the
nearby data points.
A (x1, y1), B(x2, y2), C(x3, y3), y2 is unknown, assume gradient of AB= gradient of AC
𝑦2 −𝑦1 𝑦3 −𝑦1
=
𝑥 2 −𝑥 1 𝑥 3 −𝑥 1
, 𝑦2 = 𝑦1 +
𝑦3 −𝑦1 (𝑥 2 −𝑥 1 )
𝑥 3 −𝑥 1
, 𝑦2 -unknown
Example of 8a (Nicosia):
10:12−𝑡 10:12−9:20
35−30
=
40−30
,
t=10:12 -
5∗(10:12−9:20)
10
♦Time calculation:
10:12-9:20=9:72-9:20=0:52
t=10:12-00:26=9:72-00:26=9:46
♦supplementary information for Question 10 of lab 1
Place name
Geographic location
Cape Town
33°S 18°E
Singapore
1°N 103°E
Calcutta
22°N 88°E
Buenos Aires
34°S 58°W
New Orleans
29°N 90°W