Calculators for Gnomon Skywatch

Here are some calculators for the gnomon skywatch. Enter values in the required fields and press the ``compute'' button to see the result.

Altitude calculation

Enter the stick height above the paper/cardboard, and length of the shadow. Be sure to use the same length units for the stick height and shadow length (i.e., if the stick height is measured in inches, then give the shadow length in inches!).

Also, enter any fractional amounts as decimal fractions. For example, 6 and 7/8 should be entered as 6.875.

Stick height:
Shadow length:

Here are the results
= the ratio
degrees = the altitude of the Sun

Sun Position and Observer's Location

Enter the date of your observation, the time of the shortest shadow, the number of hours ahead of the Pacific Timezone you are (e.g., 0 for California, +3 for New York, -2 for Hawii, etc.) to find the position of the real Sun and how far from the "mean Sun" it is.

Note! If you are EAST of the prime meridian (0° longitude) that goes through Greenwich, England, enter your timezone middle longitude as a NEGATIVE number---the final result will be a positive number.

Enter the date of your observation:
Enter the maximum altitude of the Sun: degrees
Enter time of maximum altitude
(or time midway between two max altitudes)
Do NOT use military time:
(Enter 00 for the seconds if you did not record the seconds)
Hour Minutes Seconds AM or PM
: : || AM
PM
Was Daylight Savings in effect?
(For most of the United States, this is between the second Sunday in March and the first Sunday in November)		 YES |-| NO
Hours ahead of the Pacific Timezone:
(Example: 0 for California, +3 for New York, -2 for Hawii)

Declination of Sun at this date and time: degrees.

Equation of Time at this date and time: minutes.
Note: Negative Eq. Time means Sun is on the meridian at time zone's meridian after 12:00 noon (Sun is slow).

Be sure to quote the Sun's declination and the Equation of Time value in your report where you write about your derived position on the Earth!

Derived Longitude from your data: degrees (West -- if you're in North or South America; East -- if you're east of the Prime Meridian 0° longitude)

Derived Latitude from your data: degrees North

If the latitude value is less than zero, you are south of the Earth's equator. Ignore the minus sign and quote your latitude as # degrees South. Remember to compare the derived longitude and latitude value with the accepted value for your observation point!

Get Latitude Longitude from Address (just enter your address and it will give the longitude and latitude. Negative longitude means WEST longitude.)

Using Google Maps to find longitude, latitude: enter your address and right click on the marker to bring up the context menu and select the "What's Here" option in the menu. The latitude and longitude will appear in the address field, latitude first then longitude as decimal degrees. The minus sign in the longitude means WEST longitude (California is WEST of the prime meridian).

To map a location given the longitude, latitude: make sure the numbers are in decimal degrees first (see the degree converter calculator if you need to convert). In Google Maps' or MapQuest's address field, enter the latitude first, a comma, and then the longitude with a minus sign if you are WEST longitude (which will be the case if you are in the US, Canada, Mexico, and most of the Pacific Ocean).

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