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09/27/2018 – Ephemeris – Twilight zone

September 27, 2018 Comments off

Ephemeris for Thursday, September 27th. The Sun will rise at 7:35. It’ll be up for 11 hours and 54 minutes, setting at 7:30. The Moon, 3 days past full, will rise at 9:12 this evening.

It will get dark tonight with the end of astronomical twilight at 9:11 p.m., and a minute later the bright Moon will rise spoiling the dark sky. Speaking of astronomical twilight there are three twilight periods: Civil, Nautical and Astronomical. In the evening civil twilight lasts from sunset to when the Sun drops to 6 degrees below the horizon. The scene around is still quite bright, but car headlights still need to be on. Nautical twilight lasts until the Sun is 12 degrees below the horizon. Bright stars and the horizon are visible for sextant use. After that is astronomical twilight until the Sun is 18 degrees below the horizon, when the stars become more and more numerous. After that it’s officially dark, Moon willing.

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

Addendum

Twilight phases by timeanddate.com.
Twilight phases

More information about twilight, dusk and dawn can be found here:  https://www.timeanddate.com/astronomy/different-types-twilight.html.

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04/06/2018 – Ephemeris – Marking the passage of 13 hours of daylight

April 6, 2018 Comments off

Ephemeris for Friday, April 6th. The Sun will rise at 7:14. It’ll be up for 13 hours and 2 minutes, setting at 8:16. The Moon, 2 days before last quarter, will rise at 2:33 tomorrow morning.

Tomorrow morning early, the crescent Moon will pass Saturn and Mars. These planets will be below the Moon in the dark early morning hours. The dark night hours will be increasingly more inaccessible as summer approaches. Today we’ve broached 13 hours of daylight. By the summer solstice on June 21st the Sun will be out just a bit over 15 and a half hours. Meaning that the Sun will be down for only eight and a half hours, with only three and a half hours of really dark sky, Moon permitting, between the end of evening astronomical twilight and the beginning of morning astronomical twilight. Twilight is really long around the summer solstice because the Sun sets at a shallow angle.

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

Addendum

Definitions

End or start of Civil Twilight:  Sun is 6° below the horizon

Brighter planets become visible

End or start of Nautical Twilight:  Sun is 12° below the horizon

Brighter deep sky objects can be found for public star parties

End or start of astronomical twilight:  Sun is 18° below the horizon

On moonless nights, the twilight glow is gone and the sky is dark

02/01/2018 – Ephemeris – Previewing February skies

February 1, 2018 1 comment

Ephemeris for Thursday, February 1st. The Sun will rise at 8:01. It’ll be up for 9 hours and 49 minutes, setting at 5:51. The Moon, 1 day past full, will rise at 7:30 this evening.

Lets look ahead at our short month of February. It’s so short that this year it has no full moons. To make up for it both January and March have two. We’re in the depths of winter but the Sun is continuing its return to northern climes. This is reflected in the increase in daylight hours, from 9 hours 49 minutes today to 11 hours 7 minutes on the 28th. These times are for the Interlochen/Traverse City area. Daylight durations are slightly shorter in the northern part of our listening area and slightly longer to the south. As the month goes on the weather should generally warm and clear up. Venus is moving away from the Sun and will become more and more visible after sunset as the month wears on. Today Venus will set 24 minutes after the Sun. This will increase to an hour after the Sun.

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

Addenda

February Evening Sky Chart

February Evening Star Chart

Star Chart for February 2018 (9 p.m. EST February 15, 2018). Created using my LookingUp program. Click on image to enlarge.

The planets and stars are plotted for the 15th at 9 p.m. EST in the evening and 6 a.m. for the morning chart. These are the chart times. Note that Traverse City is located approximately 45 minutes behind our time meridian. (An hour 45 minutes behind our daylight saving time meridian. during EDT and 45 minutes behind our daylight standard time meridian. during EST). To duplicate the star positions on a planisphere you may have to set it to 1 hour 45 minutes (Daylight Time) or 45 minutes (Standard Time) earlier than the current time if you are near your time meridian.

Note the chart times of 9 p.m. and 6 a.m. are for the 15th. For each week before the 15th add ½ hour. For each week after the 15th subtract ½ hour. The planet positions are updated each Wednesday on this blog. For planet positions on dates other than the 15th, check the Wednesday planet posts on this blog.

February Morning Star Chart

February Morning Star Chart

Star Chart for February 2018 mornings based on 6 a.m. February 15th. Created using my LookingUp program. Click on image to enlarge.

For a list of constellation names to go with the abbreviations click here.

Star chart annotations

  • Pointer stars at the front of the bowl of the Big Dipper point to Polaris the North Star.
  • Leaky Big Dipper drips on Leo.
  • Follow the arc of the handle of the Big Dipper to the star Arcturus.
  • The Summer Triangle is in red.

Twilight

Evening nautical twilight ends at 6:58 p.m. EST on the 1st, increasing to 7:31 p.m. EST on the 28th.
Evening astronomical twilight ends at 7:30 p.m. EST on the 1st, increasing to 8:04 p.m. EST on the 28th.
Morning astronomical twilight starts at 6:22 a.m. EST on the 1st, and decreasing to 5:45 a.m. EST on the 28th.
Morning nautical twilight starts at 6:56 a.m. EST on the 1st, and decreasing to 6:19 a.m. EST on the 28th.

NASA Calendar of Planetary Events

    Date    Time    Event
Feb 01 	Th	    Venus: 5.7° E
    01  Th  1:24 pm Moon-Regulus: 0.9° S
    07  We 10:54 am Last Quarter
    07  We  2:47 pm Moon-Jupiter: 4.7° S
    09  Fr 12:12 am Moon-Mars: 4.8° S
    11  Su  9:16 am Moon Apogee: 405700 km
    11  Su  9:46 am Moon-Saturn: 2.7° S
    11  Su 11:40 am Mars-Antares: 5.1° N
    11  Su  6:21 pm Moon South Dec.: 20° S
    14  We  4:11 pm Moon Descending Node
    15  Th  3:52 pm Partial Solar Eclipse - S. America, Antarctica
    15  Th  4:05 pm New Moon
    17  Sa  7:08 am Mercury Superior Conj.
    23  Fr  3:09 am First Quarter
    23  Fr 12:07 pm Moon-Aldebaran: 0.7° S
    25  Su  3:07 pm Moon North Dec.: 20.1° N
    27  Tu  9:48 pm Moon Perigee: 363900 km
    27  Tu 12:28 pm Moon-Beehive: 2.3° N
    28  We 12:03 am Moon Ascending Node
Mar 01  Th          Venus: 12.4° E

Sky Events Calendar by Fred Espenak and Sumit Dutta (NASA’s GSFC),
http://eclipse.gsfc.nasa.gov/SKYCAL/SKYCAL.html

If you go to the above site you can print out a list like the above for the entire year
or calendar pages for your time zone.

Sun and Moon Rising and Setting Events

     LU                  Ephemeris of Sky Events for Interlochen/TC
     February, 2018    Local time zone: EST
     +-----------------------------------------------------------------------+
     | DATE |  SUN     SUN  DAYLIGHT|   TWILIGHT*    |MOON  RISE OR    ILLUM |
     |      |  RISE    SET    HOURS |  END    START  |PHASE SET** TIME FRACTN|
     +=======================================================================+
     |Thu  1| 08:01a  05:51p  09:49 | 06:57p  06:55a |      Rise 07:30p   97%|
     |Fri  2| 08:00a  05:52p  09:52 | 06:58p  06:54a |      Rise 08:43p   92%|
     |Sat  3| 07:59a  05:54p  09:54 | 07:00p  06:53a |      Rise 09:53p   85%|
     +------+-----------------------+----------------+-----------------------+
     |Sun  4| 07:58a  05:55p  09:57 | 07:01p  06:52a |      Rise 11:01p   76%|
     |Mon  5| 07:57a  05:57p  10:00 | 07:02p  06:51a |      Rise 12:06a   66%|
     |Tue  6| 07:55a  05:58p  10:02 | 07:04p  06:50a |      Rise 01:09a   57%|
     |Wed  7| 07:54a  06:00p  10:05 | 07:05p  06:49a |L Qtr Rise 02:10a   47%|
     |Thu  8| 07:53a  06:01p  10:08 | 07:06p  06:48a |      Rise 03:09a   37%|
     |Fri  9| 07:51a  06:02p  10:11 | 07:07p  06:46a |      Rise 04:05a   28%|
     |Sat 10| 07:50a  06:04p  10:13 | 07:09p  06:45a |      Rise 04:57a   20%|
     +------+-----------------------+----------------+-----------------------+
     |Sun 11| 07:48a  06:05p  10:16 | 07:10p  06:44a |      Rise 05:45a   13%|
     |Mon 12| 07:47a  06:07p  10:19 | 07:11p  06:42a |      Rise 06:29a    8%|
     |Tue 13| 07:46a  06:08p  10:22 | 07:13p  06:41a |      Rise 07:07a    3%|
     |Wed 14| 07:44a  06:09p  10:25 | 07:14p  06:40a |      Rise 07:42a    1%|
     |Thu 15| 07:43a  06:11p  10:28 | 07:15p  06:38a |New   Set  06:07p    0%|
     |Fri 16| 07:41a  06:12p  10:31 | 07:16p  06:37a |      Set  07:09p    1%|
     |Sat 17| 07:40a  06:14p  10:34 | 07:18p  06:36a |      Set  08:13p    5%|
     +------+-----------------------+----------------+-----------------------+
     |Sun 18| 07:38a  06:15p  10:37 | 07:19p  06:34a |      Set  09:17p   10%|
     |Mon 19| 07:36a  06:16p  10:40 | 07:20p  06:33a |      Set  10:23p   17%|
     |Tue 20| 07:35a  06:18p  10:43 | 07:22p  06:31a |      Set  11:29p   25%|
     |Wed 21| 07:33a  06:19p  10:46 | 07:23p  06:30a |      Set  12:38a   35%|
     |Thu 22| 07:32a  06:21p  10:49 | 07:24p  06:28a |      Set  01:46a   46%|
     |Fri 23| 07:30a  06:22p  10:52 | 07:25p  06:27a |F Qtr Set  02:54a   57%|
     |Sat 24| 07:28a  06:23p  10:55 | 07:27p  06:25a |      Set  04:00a   69%|
     +------+-----------------------+----------------+-----------------------+
     |Sun 25| 07:27a  06:25p  10:58 | 07:28p  06:23a |      Set  04:59a   79%|
     |Mon 26| 07:25a  06:26p  11:01 | 07:29p  06:22a |      Set  05:52a   88%|
     |Tue 27| 07:23a  06:27p  11:04 | 07:31p  06:20a |      Set  06:38a   94%|
     |Wed 28| 07:22a  06:29p  11:07 | 07:32p  06:18a |      Set  07:17a   99%|
     +-----------------------------------------------------------------------+
     * Nautical Twilight
     ** Moonrise or moonset, whichever occurs between sunset and sunrise

 

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.

Addendum

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.

Addendum

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.

Addendum

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.

Categories: Ephemeris Program, Twilight Tags: