03/16/2021 – Ephemeris – Tonight we’ll have exactly 12 hours of night

This is Ephemeris for Tuesday, March 16th. Today the Sun will be up for 11 hours and 57 minutes, setting at 7:50, and it will rise tomorrow at 7:50. The Moon, 3 days past new, will set at 11:15 this evening.

Did you notice what I just said? Sunset’s at 7:50 pm and sunrise’s at 7:50 am. Tonight we’ll have exactly 12 hours of night. That’s what the word equinox means, equal night… But the vernal or spring equinox isn’t until Saturday when spring starts. By then night, including twilight, will be down to 11 hours, 50 minutes. The disparity comes down to modern versus older definitions. Equinox, being Latin is an older definition. The modern instant of sunrise and sunset occurs when the top of the Sun’s disc touches the sea horizon. Because our atmosphere bends light, and at its greatest when looking at the horizon, the Sun will have set already, geometrically, by the time the bottom edge of the Sun appears to touch that sea horizon. Making daylight a bit longer than you’d think.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

How the atmosphere bends the light of the Sun or Moon rising or setting to appear higher than it actually is. S is the actual position of the Sun, S’ is the apparent position of the Sun. The blue line is the observer O’s horizon. The gray line is the actual, though much exaggerated, light path bent or refracted by the Earth’s atmosphere. The black line is the apparent sight line to the Sun. Credit Francisco Javier Blanco González, 2017

01/15/2019 – Ephemeris – Welcome 8:19 a.m. listeners

Ephemeris for Tuesday, January 15th. Today the Sun will be up for 9 hours and 11 minutes, setting at 5:28, and it will rise tomorrow at 8:16. The Moon, 1 day past first quarter, will set at 3:11 tomorrow morning.

Welcome to the 8:19 a.m. listeners to this program. Due to the two-hour span from the 6:19 and 8:19 airings it was thought to always give you event times in advance, which is why I’m giving tomorrow’s sunrise times. Don’t worry tomorrow’s sunrise time will never be more than 2 minutes before or after today’s. Right now, sunrise times are retreating by a half-minute a day. It’s faster in spring and fall. For more information see my blog: bobmoler.wordpress.com. Transcripts of the program are there with illustrations and additional information. And today a way to create your own sunrise and sunset calendar.

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

Addendum

The times of rising and setting of celestial objects is accurate for only one spot on the Earth.  In the case of the times I give, it’s for my house.  There’s a good reason for it.  I live approximately half way between Interlochen and Traverse City.  In the early days I interpolated from astronomical tables in the Royal Astronomical Society of Canada’s Observers Handbook.  I preferred it to the Naval Observatory’s Astronomical Almanac, which was more expensive.  Anyway I had a relatively flat horizon everywhere but north, so if I climbed on the roof I could check out and verify the rising and setting times.   Note that the times assume a flat sea horizon.

About accurate times:  At my latitude celestial objects rise and set one minute later for each 12 1/3 miles (19.85 km) you are west of me, or a good landmark would be Traverse City West Senior High School.  For every 12 1/3 miles east of there rising and setting events would be earlier by a minute.  The correction for latitude or north and south isn’t that simple. See the illustration below:

These are snippets of calendars for three locations that are in a straight line from south-southwest to north-northeast in the IPR listening area. A line drawn perpendicular to it to the west-northwest is to the Sun’s setting point. Thus the setting times for all three locations are the same. However their rising times are the most divergent, as are the daylight hours.

On my Ephemeris website, not to be confused with the blog that you are now reading, I have rise and set calendars for:  Cadillac, Interlochen/Traverse City (Source for times on the Ephemeris program), Ludington, Mackinaw City, Petoskey, Eagle Harbor – Keweenaw Peninsula, Houghton Lake, and Earth’s Equator at the Prime Meridian.  Go Here:  http://ephemeris.bjmoler.org/calendar.htm.

If you’d like these times for a different location go to the Complete Sun and Moon Data for One Day, or Sun or Moon Rise/Set Table for One Year from the United States Naval Observatory (USNO). It calculates sunrise, sunset, moonrise, moonset, and twilight  for locations in the US and other locations world-wide.  Note that these do not follow the changes to and from Daylight Saving Time.

 

06/05/2018 – Ephemeris – Green flash

Ephemeris for Tuesday, June 5th. Today the Sun will be up for 15 hours and 25 minutes, setting at 9:24, and it will rise tomorrow at 5:58. The Moon, 1 day before last quarter, will rise at 2:16 tomorrow morning.

Now that it’s June and the season of summer is only two weeks away, thoughts run to heading out to the beach. One of the great pleasures of heading out to a Lake Michigan beach is seeing the sunset. And if the Sun sets on the cloudless horizon, a rare treat is to see the green flash. I’ve heard about it since my youth, but have seen it only once. I’ve seen the sunset many, though not a huge number of, times. The time I did, I was purposely looking for it. The green flash is when as the last part of the upper limb of the Sun disappears it suddenly turns green for a second, then it’s gone. So it’s easy to miss. The flash isn’t really brighter, but the top edge turns suddenly from reddish-orange to green as it disappears.

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

Addendum

The green flash recorded by Brocken Inaglory in January 2006 from Santa Cruz, CA. GNU Free Documentation License from the Green Flash Wikipedia page, which has more examples.

Last night’s sunset was beautiful, but didn’t promise clear skies

Just after sunset from a hill top near Suttons Bay, MI. Credit Bob Moler.

The view is across most of the Leelanau Peninsula, the Manitou Passage, and North Manitou Island at the sunlit bottoms of the clouds just after sunset.

The event was the annual Grand Traverse Astronomical Society picnic and star party.  Most of the evening was consumed by fleeting glimpses of Saturn and deep sky objects through the holes in the clouds by members telescopes and the society’s 25 inch “Dobinator” which was run by a crew headed by telescope “wrangler” Don Flegel.  Before sunset the Sun provided some glorious prominences for us.

06/15/2015 – Ephemeris – The earliest sunrise

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.

Addendum

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.

05/20/2014 – Ephemeris – Special doings at the Sleeping Bear National Lakeshore Friday Night

Ephemeris for Tuesday, May 20th.  Today the sun will be up for 14 hours and 59 minutes, setting at 9:09.   The moon, 1 day before last quarter, will rise at 2:09 tomorrow morning.  Tomorrow the sun will rise at 6:08.

This Friday evening Dr. Tyler Nordgren, astronomer, artist and dark sky advocate will give a presentation at the Sleeping Bear Dunes National Lakeshore Philip A. Hart Visitor Center in Empire at 7 p.m. Afterward he will be signing copies of his beautiful new poster See the Stars from Sleeping Bear Dunes National Lakeshore featuring the Great and Little Bear constellations and the bluffs of the Sleeping Bear Dunes and the Manitou Islands.  After that, weather permitting see the sunset from many of the parks locations, then, for the hardy, settle down for an all night vigil for a possible meteor storm with the Grand Traverse Astronomical Society at the Dune Climb (The bottom, not the top, though you can climb up there for an all-sky view.).

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

Addendum

See the Stars from Sleeping Bear Dunes National Lakeshore Poster by Tyler Nordgren.

06/26/2013 – Ephemeris – Latest sunset and the Summer Triangle

Ephemeris for Thursday, June 27th.  Today the sun will be up for 15 hours and 32 minutes, setting at 9:31.   The moon, 3 days before last quarter, will rise at 12:14 tomorrow morning.  Tomorrow the sun will rise at 5:59.

Last night we had the latest sunset of the year.  The sun is really beginning to head south.  Other than the sunrise and sunset numbers, we’ll begin to notice it for real in a few weeks.  At first that realization strikes me a sad note that summer is beginning to end.  However the astronomer in me realizes that means more night-time hours, and that the summer Milky Way is coming.  Of the three bright stars of the Summer Triangle overhead and in the east, two of its stars are in the milky band.  They are Deneb to the north and Altair to the south.  Vega, closest to the zenith is not in the band.  Actually all the stars we see with the naked eye or small telescopes belong to the Milky Way galaxy.

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

Addendum

The Summer Triangle at 11 p.m. Created using Stellaruim and The Gimp.