Wk 2 Sunshine & Shade

Question 1

What causes the seasons?

Answer 1

The 23.45’ tilt of the earth’s axis relative to its path around the sun.

Question 2

Why should we be interested in measuring the amount of sunlight that falls on an area?

Answer 2

1. ensure NEIGHBOURS receive sufficient light
2. ensure EXTERIOR/EXTERNAL AREAS receive sufficient light
3. ensure INTERNAL/INTERIOR AREAS receive sufficient light and are are sufficiently protected
4. to activate PASSIVE SOLAR HEATING

Question 3

What is the maximum altitude of the sun in WINTER?

What is the position of the sun in the sky relative to East&West?

Answer 3

WINTER - 30’

Sun well NORTH of east& west in morning & afternoon

Question 4

What is the maximum altitude of the sun in SUMMER?

What is the position of the sun in the sky relative to East&West?

Answer 4

SUMMER - 80’

Sun well SOUTH of east & west in morning & afternoon

Question 5

Where are the TROPICS?

Answer 5

between the Tropic of Cancer & the Tropic of Capricorn (23.5’N & 23.5’ S)

Question 6

What is the altitude of the sun at noon on the summer solstice?

Answer 6

= 90 - latitude + 23.5 deg

Sydney Latitude - 35’S

=90 - 35’ + 23.5 = 78.5

Question 7

What and When is the summer solstice?

Answer 7

The most Southerly Sun position and maximum noon altitude for the year. (Longest day length of year)

21 December in Southern Hemisphere

Question 8

What and When is the winter solstice

Answer 8

The most NORTHERLY sun position and MINIMUM noon altitude for the year. (Shortest day of year)

21 June in Southern Hemisphere

Question 9

What is the altitude of the sun at noon on the winter solstice?

Answer 9

= 90 - latitude - 23.5

Sydney Latitude - 35’South

=90 - 35 - 23.5 = 31.5

Question 10

What is the altitude of the sun at noon on the equinoxes?

Answer 10

90’ - (MINUS) latitude of the observer

Question 11

define ZENITH

Answer 11

the point in the sky or celestial sphere directly above an observer.

Question 12

define MERIDIAN

Answer 12

the IMAGINARY CIRCLE in the sky passing from the NORTH to SOUTH POINTS OF THE HORIZON.. through the zenith.

Question 13

define SOLAR NOON

Answer 13

the moment when the sun crosses the meridian.

at this moment the sun is at its highest altitude for the day in question

Question 14

define ALTITUDE:

Answer 14

angular height above the horizon

Question 15

When are the equinoxes?

Answer 15

21 March

23 September

Question 16

What are the equinoxes?

Answer 16

The 2 days of the year when the sun rises and sets at precisely due East & due West respectively.

With a maximum altitude at noon of 90’ minus the latitude of the observer.

Question 17

What are the equinoxes?

Answer 17

The 2 days of the year when the sun rises and sets at precisely due East & due West respectively.

With a maximum altitude at noon of 90’ minus the latitude of the observer.

Question 18

How do you calculate the noon sun altitude for a given location on the summer solstice, winter solstice & equinoxes?

Answer 18

Max altitude summer solstice = 90 - latitude + 23.5
Max altitude winter solstice = 90 - latitude -23.5
Max altitude equinoxes = 90 - latitude

Question 19

define AZIMUTH

Answer 19

The angle of plan between north and the direction of the position of the sun.

Question 20

Why is it warmer in summer than in winter?

Answer 20

Summer is warmer than winter for two reasons:
1) Sun is higher in the sky in summer, thus sunlight is more direct.

2) Sun spends more time above the horizon in summer, thus exposing Earth’s surface to warming sunshine for longer period of time.

Question 21

Define LATITUDE

Answer 21

the angular distance in degrees north or south of the equator (latitude 0’)

equal to the angle subtended at the centre of the globe by the meridian between the equator and the point.

Question 22

What is the latitude of Sydney?

Answer 22

35’S

Question 23

What are the ideal dates between which architects could/should design to exclude sun from buildings in Sydney?

Answer 23

Between 17th October and 26th February

Question 24

Ideally, what date(s) should the maximum admission of sunlight into Sydney buildings be?

Answer 24

19th July & therefore also 26 May

Question 25

How to draw shadow diagrams by hand…

Answer 25

Use solar charts contained in sunshine and shade in Australia

Question 26

How to read the azimuth and altitude from a solar chart

Answer 26

1. Choose chart representing appropriate Latitude (Sydney 35’S)
2. What everything means:
   * The thick black arcs represent the path of the sun on specified dates of the year.
   * The concentric circles represent different angles of altitude (follow the circle back to the vertical bar to read the altitude)
   * The short lines intersecting all the arcs of the sun path represent the times of day
   * The outer circle (that looks like a compass) that is marked with angles - represent the Azimuth for the particular days at particular times.
3. Reading off the solar chart…. e.g. 9AM March 21

> > > > locate the sun path for March 21
Place a dot on the point where the sun path intersects the 9AM line
AZIMUTH: Trace a line from the origin of the chart (0,0/ the very centre) to the outer ring - this is the AZIMUTH. the Azimuth at 9AM on March 21 is 60’ EAST OF NORTH
ALTITUDE: Now go back to the point you marked earlier (for 9AM March 21) and follow the line of the altitude circle around to the Y Axis to read the angle of altitude. The altitude of the sun at 9AM on March 21 is 35’.