Posts Tagged ‘DISCOVR’

03/20/2017 – Ephemeris – Spring starts today!

March 20, 2017 Comments off

Ephemeris for Monday, March 20th.  The Sun will rise at 7:45.  It’ll be up for 12 hours and 10 minutes, setting at 7:55.  The Moon, at last quarter today, will rise at 3:39 tomorrow morning.

This morning, at 6:29 (10:29 UT) the sun crosses overhead at the earth’s equator as it appears to head north, starting for us the season of spring.  It’s the vernal equinox.  As you can tell from my intro, we’re already above 12 hours of daylight, and we’ll add another 3 plus hours of daylight before summer begins in three months.  We are already adding about 3 minutes a day of daylight to that goal now, the maximum rate.  With the Sun out longer and its ascension higher in the sky each day, it is rapidly adding energy to the northern hemisphere.  We don’t feel that immediately.  While the land rapidly absorbs heat, the oceans and lakes, especially the Great Lakes are a big heat sink, taking a very long time to warm up.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.


This March equinox also is the beginning of autumn for folks south of the equator.

Earth near equinox

Image from the DISCOVR satellite in halo orbit at the Earth-Sun L1 point, nearly a million miles (1.6 million km) sunward of the Earth. as of March 17, 2017. As usual Michigan is covered by a cloud.  Credit NOAA/NASA.


12/21/2015 – Ephemeris – Except for 12 minutes today is the last day of autumn.

December 21, 2015 Comments off

Ephemeris for Monday, December 21st.  The Sun will rise at 8:16.  It’ll be up for 8 hours and 48 minutes, setting at 5:04.   The Moon, 3 days past first quarter, will set at 4:50 tomorrow morning.

Here we are at the mostly last day of autumn.  The last 12 minutes will be the start of winter.   The winter solstice will occur at 11:48 this evening, here in the Eastern Standard Time Zone.  Next year winter will start 18 hours earlier.  The reason is that next year is a leap year and the addition of an extra day will push all the solstices and equinoxes back by about 18 hours.  Why only 18 hours?  18 hours is three-quarters of a day, and by this time next year we will have used up a quarter of that adjustment already.  The Earth takes approximately 365 and a quarter days to orbit the Sun, so a day is added every 4th year, except century years not divisible by 400.  I’ll discuss more about the implications of the solstice tomorrow.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.


The Earth near December solstice

Not quite the solstice, this is the Earth on December 16th, 2015 taken by the EPIC camera on the DISCOVR spacecraft at the Sun-Earth L1 point, some 1.5 million miles (1 million km) from the Earth.  Credit:  NOAA.