Sun and moon positions

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Reference locations Show moon on chart
Sunshine0Watts per square meter
UV dose0% of max
Moon0% full
Moonshine0% full

This page tells you where the sun and moon are in the sky for a given time and place. The "latitude" slider lets you move north and south, and the "longitude" slider moves the observation position east and west. An initial guess is made based on the computer's timezone. A modern browser will attempt to estimate your location more precisely, if you allow it. The "date offset" slider changes the date by up to half a year. The "time offset" slider changes the time by up to half a day. The reference locations go to preset latitudes and longitudes, but the time zone does not change.

Altitude: 0 = horizon, 90 = straight up (0 = edge, 90 = center of plot)
Azimuth: degrees clockwise from north (north = top of plot)
At the north or south pole, the program assumes you are a few steps off the pole so that your longitude is still valid.

Sunshine units are watts per square meter incident on a panel facing the sun. UV is the amount of radiation compared to that with the sun directly overhead. The program assumes standard sea-level, clear-sky conditions.

The rise and set times can be a few minutes off, and do not include the seasonal or monthly rises and sets near the poles. The effect of atmospheric refraction is not included.

The "rise and set chart" button will produce a plot below showing rise and set times for a year beginning at the current date. The chart area is blue when the sun is up. When the moon is up, it is shown by a white stripe with opacity proportional to the moon brightness. Vertical gridlines indicate the start of a month. Be sure to use a longitude in your time zone, or set the desired time zone in your system clock and refresh the page.

The javascript for this page draws upon several sources described in the source code, including an ancient version of John Thorstensen's SkyCalc and information in the Astronomical Almanac.

Your browser does not support the HTML5 canvas tag, so the plot cannot be drawn.