Home Search GeoAstro Applets Astronomy Chaos Game Java Miscel- laneous Physics Quiz Who is Who ?

Cole Universal Sun Compass

See also:
Sundial in a Box

Applet instructions:

 To change the input of the "Home Latitude" text field click into the applet area within the red frame first. Enter your latitude in decimal degrees, northern positive, southern negative. In case you don't want to draw the ellipse for your home latitude enter "0" into the "Home Latitude" text field. Enter your longitude in decimal degrees, eastern positive, western negative, then hit the button "Apply input" ! Select from the "Details" menu.

 The pattern of the Sun Compass disk consists of ellipses, each corresponding to a particular latitude, crossed by hyperbola, corresponding to the local apparent time hours. The gnomon has to be placed on the current day of the date scale (divided by intervals of 7 days) taking into account the change of the Sun's declination. To use the compass, the shadow must be kept on the local apparent time of day along the correct ellipse for the latitude of the place. The 12 hours line is pointing True North then.

 The hours on the disk above are Local Apparent Time (LAT), which is computed from Standard Time (ST) taking into account the longitude of own position, the longitude of the Standard Time, and the equation of time (EQT), . The correction (D) is +4 minutes per degree of longitude East of Standard Time, or -4 minutes per degree of longitude West of Standard Time, plus the equation of time (EQT): LAT = ST + D +  EQT Example: For a location at 10° E the longitude of Standard Time is 15° E, thus D=5*(-4min)=-20min. For EQT=-12min, Standard Time 15:00, the Local Apparent Time is: LAT = 15:00 - 00:20 - 00:12 = 14:28

Example: February 15, latitude 56° N, 14:30 local apparent time.

Details about the azimuth angle of the Sun

 Web Links

Updated: 2013, Feb 08