Archive for the ‘Twilight’ Category

09/20/2016 – Ephemeris – The twilight zone

September 20, 2016 Comments off

Ephemeris for Tuesday, September 20th.  The Sun will rise at 7:28.  It’ll be up for 12 hours and 14 minutes, setting at 7:43.  The Moon, 3 days before last quarter, will rise at 10:29 this evening.

It’s getting a lot darker a lot earlier now than it did a month or so ago.  We see the same thing in the morning sky.  Now astronomical twilight, that’s when the last vestiges of the twilight glow disappear, ends before the time of sunset we had back in June.  Tonight that’s at 9:21 p.m., when the Sun reaches 18 degrees below the horizon.  Useful stargazing usually starts by nautical twilight which will occur at 8:46 p.m. when the Sun is 12 degrees down.  This is the time when navigators could see the bright stars and the horizon with their sextants to make a star fix.  It is a time when all the naked eye planets and the brighter constellations can be made out.   Twilight lasts the longest near the summer solstice due to the shallow angle of the Sun’s setting path.

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


Below is the twilight table for September through December.  This is a calendar function from Cartes du Ciel (Sky Charts), a free program, which can be downloaded from the panel on the right of this page.  This is, of course, for the Interlochen/Traverse City, Michigan area.  If you’re from somewhere else, download the program, and put in your location to create your own table.  The last two columns on the right are times that the sky will be dark, without moonlight.

Interlochen/ Traverse City Time zone=EDT/EST
Morning twilight Evening twilight Dark night
Date Astronomical Nautical Nautical Astronomical Start End
2016-09-01 5h26m 6h04m 21h27m 22h05m 22h05m 5h26m
2016-09-02 5h28m 6h06m 21h25m 22h03m 22h03m 5h28m
2016-09-03 5h29m 6h07m 21h23m 22h01m 22h01m 5h29m
2016-09-04 5h31m 6h09m 21h21m 21h59m 21h59m 5h31m
2016-09-05 5h33m 6h10m 21h19m 21h56m 22h24m 5h33m
2016-09-06 5h34m 6h11m 21h17m 21h54m 22h55m 5h34m
2016-09-07 5h36m 6h13m 21h15m 21h52m 23h29m 5h36m
2016-09-08 5h37m 6h14m 21h13m 21h50m 5h37m
2016-09-09 5h39m 6h15m 21h11m 21h48m 0h07m 5h39m
2016-09-10 5h40m 6h17m 21h09m 21h45m 0h50m 5h40m
2016-09-11 5h42m 6h18m 21h07m 21h43m 1h39m 5h42m
2016-09-12 5h43m 6h19m 21h05m 21h41m 2h34m 5h43m
2016-09-13 5h44m 6h20m 21h03m 21h39m 3h35m 5h44m
2016-09-14 5h46m 6h22m 21h01m 21h37m 4h40m 5h46m
2016-09-15 5h47m 6h23m 20h59m 21h35m
2016-09-16 5h49m 6h24m 20h57m 21h33m
2016-09-17 5h50m 6h26m 20h55m 21h31m
2016-09-18 5h51m 6h27m 20h53m 21h28m
2016-09-19 5h53m 6h28m 20h51m 21h26m 21h26m 21h47m
2016-09-20 5h54m 6h29m 20h49m 21h24m 21h24m 22h28m
2016-09-21 5h56m 6h31m 20h47m 21h22m 21h22m 23h15m
2016-09-22 5h57m 6h32m 20h45m 21h20m 21h20m
2016-09-23 5h58m 6h33m 20h43m 21h18m 21h18m 0h06m
2016-09-24 6h00m 6h34m 20h41m 21h16m 21h16m 1h02m
2016-09-25 6h01m 6h36m 20h39m 21h14m 21h14m 2h01m
2016-09-26 6h02m 6h37m 20h37m 21h12m 21h12m 3h03m
2016-09-27 6h04m 6h38m 20h36m 21h10m 21h10m 4h05m
2016-09-28 6h05m 6h39m 20h34m 21h08m 21h08m 5h08m
2016-09-29 6h06m 6h41m 20h32m 21h06m 21h06m 6h06m
2016-09-30 6h08m 6h42m 20h30m 21h04m 21h04m 6h08m
2016-10-01 6h09m 6h43m 20h28m 21h02m 21h02m 6h09m
2016-10-02 6h10m 6h44m 20h26m 21h00m 21h00m 6h10m
2016-10-03 6h11m 6h45m 20h24m 20h58m 20h58m 6h11m
2016-10-04 6h13m 6h47m 20h22m 20h56m 21h28m 6h13m
2016-10-05 6h14m 6h48m 20h21m 20h55m 22h04m 6h14m
2016-10-06 6h15m 6h49m 20h19m 20h53m 22h45m 6h15m
2016-10-07 6h16m 6h50m 20h17m 20h51m 23h31m 6h16m
2016-10-08 6h18m 6h52m 20h15m 20h49m 6h18m
2016-10-09 6h19m 6h53m 20h14m 20h47m 0h21m 6h19m
2016-10-10 6h20m 6h54m 20h12m 20h46m 1h19m 6h20m
2016-10-11 6h21m 6h55m 20h10m 20h44m 2h20m 6h21m
2016-10-12 6h23m 6h56m 20h08m 20h42m 3h26m 6h23m
2016-10-13 6h24m 6h58m 20h07m 20h40m 4h36m 6h24m
2016-10-14 6h25m 6h59m 20h05m 20h39m 5h49m 6h25m
2016-10-15 6h26m 7h00m 20h03m 20h37m
2016-10-16 6h28m 7h01m 20h02m 20h35m
2016-10-17 6h29m 7h03m 20h00m 20h34m
2016-10-18 6h30m 7h04m 19h58m 20h32m 20h32m 21h07m
2016-10-19 6h31m 7h05m 19h57m 20h31m 20h31m 21h58m
2016-10-20 6h33m 7h06m 19h55m 20h29m 20h29m 22h54m
2016-10-21 6h34m 7h07m 19h54m 20h27m 20h27m 23h54m
2016-10-22 6h35m 7h09m 19h52m 20h26m 20h26m
2016-10-23 6h36m 7h10m 19h51m 20h24m 20h24m 0h56m
2016-10-24 6h37m 7h11m 19h49m 20h23m 20h23m 1h59m
2016-10-25 6h39m 7h12m 19h48m 20h22m 20h22m 3h01m
2016-10-26 6h40m 7h14m 19h46m 20h20m 20h20m 4h02m
2016-10-27 6h41m 7h15m 19h45m 20h19m 20h19m 5h02m
2016-10-28 6h42m 7h16m 19h44m 20h17m 20h17m 6h02m
2016-10-29 6h43m 7h17m 19h42m 20h16m 20h16m 6h43m
2016-10-30 6h45m 7h18m 19h41m 20h15m 20h15m 6h45m
2016-10-31 6h46m 7h20m 19h40m 20h14m 20h14m 6h46m
2016-11-01 6h47m 7h21m 19h38m 20h12m 20h12m 6h47m
2016-11-02 6h48m 7h22m 19h37m 20h11m 20h42m 6h48m
2016-11-03 6h49m 7h23m 19h36m 20h10m 21h26m 6h49m
2016-11-04 6h51m 7h24m 19h35m 20h09m 22h14m 6h51m
2016-11-05 6h52m 7h26m 19h34m 20h08m 23h08m 6h52m
2016-11-06 5h53m 6h27m 18h33m 19h07m 23h07m 5h53m
2016-11-07 5h54m 6h28m 18h31m 19h06m 5h54m
2016-11-08 5h55m 6h29m 18h30m 19h04m 0h09m 5h55m
2016-11-09 5h56m 6h31m 18h29m 19h03m 1h15m 5h56m
2016-11-10 5h58m 6h32m 18h28m 19h03m 2h24m 5h58m
2016-11-11 5h59m 6h33m 18h27m 19h02m 3h36m 5h59m
2016-11-12 6h00m 6h34m 18h26m 19h01m 4h50m 6h00m
2016-11-13 6h01m 6h35m 18h26m 19h00m
2016-11-14 6h02m 6h36m 18h25m 18h59m
2016-11-15 6h03m 6h38m 18h24m 18h58m
2016-11-16 6h04m 6h39m 18h23m 18h57m 18h57m 19h38m
2016-11-17 6h06m 6h40m 18h22m 18h57m 18h57m 20h39m
2016-11-18 6h07m 6h41m 18h22m 18h56m 18h56m 21h43m
2016-11-19 6h08m 6h42m 18h21m 18h55m 18h55m 22h47m
2016-11-20 6h09m 6h43m 18h20m 18h55m 18h55m 23h52m
2016-11-21 6h10m 6h45m 18h20m 18h54m 18h54m
2016-11-22 6h11m 6h46m 18h19m 18h54m 18h54m 0h54m
2016-11-23 6h12m 6h47m 18h18m 18h53m 18h53m 1h56m
2016-11-24 6h13m 6h48m 18h18m 18h53m 18h53m 2h55m
2016-11-25 6h14m 6h49m 18h17m 18h52m 18h52m 3h54m
2016-11-26 6h15m 6h50m 18h17m 18h52m 18h52m 4h52m
2016-11-27 6h16m 6h51m 18h17m 18h52m 18h52m 5h51m
2016-11-28 6h17m 6h52m 18h16m 18h51m 18h51m 6h17m
2016-11-29 6h18m 6h53m 18h16m 18h51m 18h51m 6h18m
2016-11-30 6h19m 6h54m 18h16m 18h51m 18h51m 6h19m
2016-12-01 6h20m 6h55m 18h15m 18h50m 19h11m 6h20m
2016-12-02 6h21m 6h56m 18h15m 18h50m 20h03m 6h21m
2016-12-03 6h22m 6h57m 18h15m 18h50m 20h59m 6h22m
2016-12-04 6h23m 6h58m 18h15m 18h50m 22h00m 6h23m
2016-12-05 6h24m 6h59m 18h15m 18h50m 23h03m 6h24m
2016-12-06 6h25m 7h00m 18h15m 18h50m 6h25m
2016-12-07 6h26m 7h01m 18h15m 18h50m 0h08m 6h26m
2016-12-08 6h26m 7h02m 18h15m 18h50m 1h17m 6h26m
2016-12-09 6h27m 7h03m 18h15m 18h50m 2h26m 6h27m
2016-12-10 6h28m 7h03m 18h15m 18h50m 3h40m 6h28m
2016-12-11 6h29m 7h04m 18h15m 18h50m 4h54m 6h29m
2016-12-12 6h30m 7h05m 18h15m 18h51m 6h09m 6h30m
2016-12-13 6h30m 7h06m 18h15m 18h51m
2016-12-14 6h31m 7h06m 18h16m 18h51m
2016-12-15 6h32m 7h07m 18h16m 18h51m 18h51m 19h21m
2016-12-16 6h32m 7h08m 18h16m 18h52m 18h52m 20h28m
2016-12-17 6h29m 7h04m 18h13m 18h48m 18h48m 21h35m
2016-12-18 6h30m 7h05m 18h13m 18h48m 18h48m 22h40m
2016-12-19 6h30m 7h06m 18h13m 18h49m 18h49m 23h44m
2016-12-20 6h31m 7h06m 18h14m 18h49m 18h49m
2016-12-21 6h31m 7h07m 18h14m 18h50m 18h50m 0h45m
2016-12-22 6h32m 7h07m 18h15m 18h50m 18h50m 1h46m
2016-12-23 6h32m 7h07m 18h15m 18h51m 18h51m 2h44m
2016-12-24 6h32m 7h08m 18h16m 18h51m 18h51m 3h43m
2016-12-25 6h33m 7h08m 18h17m 18h52m 18h52m 4h40m
2016-12-26 6h33m 7h09m 18h17m 18h53m 18h53m 5h37m
2016-12-27 6h34m 7h09m 18h18m 18h53m 18h53m 6h32m
2016-12-28 6h34m 7h09m 18h19m 18h54m 18h54m 6h34m
2016-12-29 6h34m 7h09m 18h19m 18h55m 18h55m 6h34m
2016-12-30 6h34m 7h10m 18h20m 18h56m 18h56m 6h34m
2016-12-31 6h34m 7h10m 18h21m 18h56m 19h53m 6h34m

03/03/2016 – Ephemeris – How to spot Zodiacal Light

March 3, 2016 Comments off

Ephemeris for Thursday, March 3rd.  The Sun will rise at 7:15.  It’ll be up for 11 hours and 17 minutes, setting at 6:33.   The Moon, 2 days past last quarter, will rise at 4:00 tomorrow morning.

There is a faint glow in the west that lingers after the end of twilight. It is visible to the careful observer.  It’s Zodiacal Light, the reflected glow from countless bits of dust in the plane of the solar system.  Its glow can be seen after twilight officially ends at 8:11 p.m.  You’ll need to go to a spot with no towns or cities immediately to the west of you.  The glow will appear as a thin pyramidal glow tilted to the left.  It’s very difficult to find the first time, but once seen you’ll easily find it again.  Zodiacal Light is easiest seen on spring evenings and autumn mornings when the ecliptic, the path of the planets and zodiac are nearest to vertical.  The farther south one goes the easier it is to see.  I first saw it when I was stationed in the Air Force in Louisiana.

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


Zodiacal Light and Comet Hale-Bopp April 1997

Zodiacal Light and Comet Hale-Bopp April 1997. My image.

Zodiacal Light and Comet Hale-Bopp April 1997. Enhanced contrast.

Zodiacal Light and Comet Hale-Bopp April 1997. Enhanced contrast.

I find I have better luck photographing Zodiacal Light if I take  picture in its general direction of something else.


08/29/2014 – Ephemeris – Twilight is shorter now than it was in June

August 28, 2014 2 comments

Ephemeris for Friday, August 29th.  The sun will rise at 7:01.  It’ll be up for 13 hours and 22 minutes, setting at 8:24.   The moon, half way from new to first quarter, will set at 10:09 this evening.

Here we are at the end of August already.  We have one more night to view the Milky Way in darkness after the moon sets, because the Moon sets at the very end of astronomical twilight.  By the way, astronomical twilight starts and ends when the sun is 18 degrees below the horizon, and the actual twilight glow is completely gone.  The sun sets more than an hour before it did in late June, which means that it gets dark much earlier.  Twilight lasted much longer in June than it does now because the Earth’s rotation now drops the sun below the horizon at a steeper angle.   As a matter of fact while the sun sets an hour earlier now than in June, twilight ends two hours earlier.  It sneaks up on you if you’re not paying attention to it.

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


Tonight's end of astronomical twilight

Distance the Sun must travel from the horizon to 18 degrees below tonight, August 29, 2014. Created using Stellarium.

 Solstice end of twilight

Distance the Sun must travel from the horizon to 18 degrees below, the night after the June solstice, June 22, 2014. Created using Stellarium.

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