sun rise-set.ppt
DESCRIPTION
What are the factors affecting sunrise and sunset timingTRANSCRIPT
Phase 1
Theoretical rising and setting of sun Visible rising and setting of sun Factors affecting sunrise and sunset Continuous sunlight.
Phase 2
Extraction of Sunrise & Sunset times - Air Almanac Corrections for Height of the Observer
THEORETICAL SUNRISE AND SUNSET
“The theoretical sunrise or sunset is said to
occur when the centre of the Sun is on the
Celestial Horizon of the observer”.
THEORETICAL SUNRISE
Celestial Horizon
THEORETICAL SUNSET
Celestial Horizon
Z
NCP
C
H
E Q
Z
NCP
C
H
E Q
SCP SCP
THEORETICAL SUNRISE AND SUNSET
90º 90º
Altitude of sun is 0 & Zenith Distance 90
VISIBLE SUNRISE AND SUNSET
“ When the upper limb of the sun is on the visible
horizon, visible sunrise or visible sunset is said to occur.
At visible s/r or s/s the body has a depression equal to
atmospheric refraction + the Semi-diameter (SD) of the
sun below the sensible horizon.
VISIBLE SUNRISE & SUNSET
Refraction
Visible Horizon
Sensible Horizon
SUN’S DEPRESSION
Visible Horizon
Sensible Horizon
Refraction
Semi-Diameter
Depression
DEPRESSION
At sunrise or sunset the upper limb of the sun is on the visible horizon, its depression below the celestial or sensible horizon is Depression = Atmospheric refraction at 0 alt + Semi diameter = 34 ’+ 16’Depression = 50 ’
Zenith distance = 90 50’
The prediction of timings of sunrise and sunset tabulated in the Air Almanac are calculated using this value.
FACTORS AFFECTING
SUNRISE AND SUNSET.
FACTORS AFFECTING
SUNRISE AND SUNSET
• Declination• Latitude• Longitude• Height of the observer
VARIATION x DECLINATION
Dec- 20
Dec- d1
Dec- d2VH
Z
NCP
EQ
NCP
EQ
VH
Dec- 10
Dec- Lat Same Name Dec- Lat Contrary Name
VARIATION WITH DECLINATION
When the sun’s declination is of the same name to the observers latitude Sun rises early and sets later with increase in sun’s declination.
When the sun’s declination is of the contrary name to the observers latitude Sun rises later and sets early with increase in sun’s declination.
VARIATION OF SUNRISE - LATITUDE
Sun’s Daily Path
Dec & Lat - Same Name
Sun rises Earlier with increase in latitude
VH 1
Z1
VH 2
Z2
NCP
EQ
Declination Same Name
VARIATION OF SUNSET - LATITUDE
Dec & Lat - Same Name
Sun sets Later with increase in latitude
Sun’s Daily Path
VH 1
Z1
VH 2
Z2
NCP
EQ
Declination Same Name
VARIATION OF SUNRISE - LATITUDE
Sun’s Daily Path
Dec & Lat - Contrary Name
Sun rises Later with increase in latitude
VH 2
Z2
VH 1
Z1
NCP
EQ
Declination Contrary Name
VARIATION OF SUNSET - LATITUDE
Dec & Lat - Contrary Name
Sun Sets Earlier with increase in latitude
Sun’s Daily Path
VH 2
Z2
VH 1
Z1
NCP
EQ
Declination Contrary Name
VARIATION WITH LATITUDE
When the sun is in the observer’s
hemisphere it rises earlier and sets later the
increase in observers latitude.
When sun is on the other hemisphere
it rises later and sets earlier with increase in
latitude.
VARIATION WITH LONGITUDE
For a given latitude and declination the local times of
sunset and sun rise for all meridians will be the same since the
relationship between times and that between hour angles are
comparable.
LHA = GHA + LONG (E/W) and
LMT = GMT + LONG (E/W) converted in time.
Thus if the declination is constant on a given latitude the
local time of rising or setting at Greenwich (GMT) would be the
same as the LMT of that at any other meridian
VARIATION WITH HEIGHT
For an Observer at a height
Sun rises Earlier and sets Later
Horizon at sea level
Horizon at 20,000 ft
Sunrise at 20,000 ft
Sunrise at sea level
Observer at 20,000 ft
HEIGHT OF THE OBSERVER
With an increase of height the sun rises earlier and sets
later due to the change in the plane of the observers
horizon.
CONTINUOUS SUNLIGHT AND
NO SUNLIGHT
At higher latitudes the sun may be above the
horizon throughout the day. This is known as
Continuous Sunlight.
Similarly sun can also be below the horizon
and not visible throughout the day which is called
No Sunlight
Calculate the Sunrise for 33 20 N, 115 13E,
on 01 Jan 1987.
Page no A130;
For 02 Jan.
Time of sunrise for 35 N = 07 08
Time of sunrise for 30 N = 06 56
Sunrise for 33 20’ N = 0704 (LMT)
Calculate the Sunrise for 78 N, on 10 Mar 1987.
Page no A153;
Time of merpass = 12 10
The semi duration from graph = 4:45
LMT of Sunrise = 1210 - 4:45 = 0725
Similarly LMT sunset = 1655