Select a location from the City pulldown menu, OR select "Enter Lat/Long ->" from the pulldown menu, and manually enter the latitude, longitude and time zone information in the appropriate text boxes. For this calculator, latitude is positive to the NORTH, and longitude is positive to the WEST of the prime meridian.

Latitude and Longitude can be in deg/min/sec, or decimal degrees entered in the "Deg:" field. (If you enter decimal degrees in the degrees field, please clear the minutes and seconds fields, or they will be added in.) If you select a city from the pulldown menu, the latitude, longitude and time zone fields will be filled in by the program. If you want to input latitude, longitude or time zone manually, be sure to select "Enter Lat/Long -->" from the City pulldown box, or your numbers will be overwritten by the selected city's location.

You can enter a different time zone for a location by selecting "Enter Lat/Long -->" in the City pulldown box. Otherwise the time zone associated with the selected city's Local Standard Time will be automatically entered. Selecting "Yes" in the Daylight Saving field will cause the solar position calculation to assume the current time has been adjusted forward one hour from standard time. If you are uncertain of the time zone for a location, refer to Time Zone Table.

The program retrieves the current date and time from your computer, and fills in these values in the date/time fields. To perform calculations for a different date, simply select the month in the pulldown box, and enter the day and four digit year in the appropriate input boxes. Time of day for the calculation can be changed in the same way.

Hit the "Calculate Solar Position" button. Once the calculations are complete, you may use your browser's "Print" function to obtain a hardcopy of the results. Results are given in the following units: Equation of Time in minutes of time; Solar Declination in degrees, with positive to the north; Azimuth in degrees clockwise from north; Elevation in degrees up from the horizon; Cosine of Solar Zenith Angle is unitless.

Note that for latitudes greater than 72° north or less than 72° south, accuracy may be lower due in part to the effects of atmospheric refraction.