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Physics Quiz

Altitude Dial Applet

This horizontal sundial tells the time by measuring the altitude angle of the Sun. The gnomon is located in the  center of the dial and perpendicular to the dial plate.
At first  rotate the dial until the shadow of the gnomon will fall on the radius of the current date.
Read the time (standard or apparent) at the end of the shadow using the hour curves. But it can't be used near surise and sunset.
The Sundial Garden of the Deutsches Museum (Munic) is showing this kind of dial in action (calculated and constructed Yves Opizzo and Christian Tobis).

standard time

Check your time zone offset and select the local standard time.


Click the applet first!
Enter latitude in decimal degrees (southern negative)

enter longitude in decimal degrees (western negative),

then press "Apply input".

You may use the keys "y", "m", "d", "h", "n" to increase the year, month, date, hour, minute, or Shift key and "y", "m", "d", "h", "n" to decrease the year, month, date, hour, minute !

Click into the circle to get the date and the altitude angle at the location of the cross hair cursor.
apparent solar
                  timestandard time
Check the box to choose apparent (solar) time, uncheck for standard time.
apparent time
                  standard time
Select from the "Options" menu.
"on/off" items are working in toggle mode.
                  altitude equation of time rise set
The times of transit, sunrise, and sunset are standard time.

North Finder

My Sundial Applets

Applets: Ancient Sundials and Quadrants

Web Links

The Sundial Primer: Spider Sundials

Horizontal Spider Sundial

Sonnenuhren-Spinne (Wikipedia)

Spinnensonnenuhr / Cadran solaire du type araignée (Yves Opizzo)

The Sundial Garden (Deutsches Museum Munic)

Last Modified: 20.10.2023

© 2009-2023 Juergen Giesen