Home > Concepts, Ephemeris Program > 06/15/2015 – Ephemeris – The earliest sunrise

06/15/2015 – Ephemeris – The earliest sunrise

June 15, 2015

Ephemeris for Monday, June 15th.  Today the Sun will be up for 15 hours and 33 minutes, setting at 9:30.   The Moon, 1 day before new, will rise at 6:19 tomorrow morning.  Tomorrow the Sun will rise at 5:56.

This is the day of the earliest sunrise.  We are still six days from the summer solstice, that day the Sun stays up the longest. And 11 days from the latest sunset.  I could be off a day since I don’t calculate sunrise and sunset times to the second.  I use the standard formula for these computations, which, among other things assumes that the horizon is the sea horizon.  If you’re standing on the bluffs overlooking Lake Michigan, sunset would be slightly later than one seen down on the shore, and for the Sleeping Bear Dunes or Empire Bluff, your sunset would be 2 minutes later that Traverse City or Interlochen anyway because that’s west of them.  At the latitude of 45 degrees the rise and set times are 1 minute later for each 12 and a half miles west you are.

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


The discussion turned from sunrises to sunsets.  Well, sunsets are a bigger deal this side of the state.  I suppose that if I lived in Alpena or Rogers City, I’d be more interested in sunrises.  The timing difference for the rising and setting of celestial objects depends on the longitude one is versus the longitude of the position for which it is calculated, as long as one stays at roughly the same latitude.  The times for this program are for a position roughly half way between Interlochen and Traverse City.  Full disclosure:  It’s the Moler homestead.  Back, when I started this program in 1975, it was an era I call BC.  Before Computers, well before personal computers.  I used the rising and setting tables from the Royal Canadian Astronomical Society’s Observer’s Handbook for the year in question, adjusting for longitude.  I climbed op on my rooftop to verify the times several times a year.  That was back when my house wasn’t surrounded by trees.

In the sky east or west, what we call longitude on the Earth is marked not in degrees, but in hours, minutes and seconds.  Since 360 degrees or Earth’s rotation equals 24 hours, one hour equals 15 degrees, and each degree equals 4 minutes.  In Traverse City, near 45 degrees north latitude,  The longitude lines are closer than at the equator.  They are 71% that of the equatorial separation.  Working it out, each minute of rotation equates to 12.31 miles.  The 12 1/2 miles is close enough for radio, and besides I had calculated it a looooong time ago and was pulling it off the top of my head.  I recalculated it just now.

Any change time in the rising and setting of objects for persons north or south of the standard position depends on the object’s declination (latitude in the sky) north of south of the celestial equator, so the calculation isn’t as simple.

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