Monthly Sunrise, Sunset and Twilights


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For today's and yesterday's sea and weather conditions, click here.

For more information, please contact: Tony Amos at afamos@utmsi.utexas.edu

Information about the Sunrise Sunset Twilight Calendar:

The table lists the time of sunrise (RISE), sunset (SET) and the length of daylight (LNGTH) for each day of the 2006 year for Port Aransas, Texas at 27 50.2'N, 097 02.9'W. It also lists two of the twilights, CIVIL and NAUTICAL. In these cases the table lists the start (START) of twilight in the morning and the end (END) of twilight in the evening. The length (LNGTH) is the length of day including the two periods of twilight.

* CIVIL TWILIGHT is defined as the period before sunrise and after sunset when one can still see and distinguish objects at ground level and the horizon is distinct. In some countries this determines when it is legal to turn on headlights on automobiles. It occurs when the center of the sun is 6 degrees below the horizon.

* NAUTICAL TWILIGHT is defined as the period before sunrise and after sunset when objects at ground level can be seen but their outline is indistinct and the horizon is indistinct. It is not possible to do outdoor operations without additional illumination. It occurs when the center of the sun is 12 degrees below the horizon.

There is an additional period of twilight (Astronomical Twilight) recognized and it occurs when the center of the sun is 18 degrees below the horizon. After that ... "Baby it's Dark out There!"

The final column (LAN) is the time of Local Apparent Noon. This is the time of day when the sun is at it's highest point in the sky, expressed in local time. This is of interest especially to scientists doing biological research and to those of you wanting to know when UV radiation is at its peak (put sunscreen on!). Note: All times are given in our local time which is Central Standard and Central Daylight Time.

If you would like a similar calendar for other locations or need Astronomical Twilight calculated, please contact Tony Amos at afamos@mail.utexas.edu. There will be a modest charge (a donation to the ARK)