PX158 - B2 - maximum altitude

alt/az grid

• for a local observer

• altitude is defined as:
  $0\mathrm{°}=horizon$
  $90\mathrm{°}=directlyoverhead$

• meridian is the north-south line for any observer

• objects reach the maximum altitude as they cross the meridian
  
  $\delta =Dec$ , $\varphi =$ latitude of the observer

for $\delta <\varphi$

for $\delta >\varphi$

• eg: what is the maximum altitude for the sun at the winter solstice from coventry?

  • at winter solstice, $Dec=-23.5\mathrm{°}$ :
  $$al{t}_{max}=90\mathrm{°}-(52-23.5)\mathrm{°}=14.5\mathrm{°}$$

• this method can be used to find the observer's longitude if the declination and the maximum altitude of an object for the observer is known

• the altitude of an object in the sky can be measured using a sextant

• the latitude can be determined using a very accurate clock