08/31/2021 – Ephemeris – Previewing September skies

This is Bob Moler with Ephemeris for Tuesday, August 31st. Today the Sun will be up for 13 hours and 16 minutes, setting at 8:20, and it will rise tomorrow at 7:05. The Moon, 1 day past last quarter, will rise at 1:07 tomorrow morning.

Let’s look at the skies for the month of September. The sun will be moving at its greatest speed in its retreat to the south. Daylight hours in the Interlochen/Traverse City area and will drop from 13 hours and 13 minutes tomorrow to 11 hours and 44 minutes on the 30th. The altitude of the Sun above the southern horizon at local noon will be 54 degrees tomorrow, and will descend to 42 degrees on the 30th. Local noon at mid-month will be around 1:37 pm. The season of summer is getting short, so enjoy it while you can. Summer ends and autumn begins at 3:21 p.m. on September 22nd, the autumnal equinox. This year the Harvest Moon, the nearest full moon to the equinox, will fall two days before it on the 20th.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.

Addendum

September Star Chart

Star Chart for September 2021. Created using my LookingUp program. Click on the image to enlarge it. Created using my LookingUp program.

The planets and stars are plotted for the 15th at 10 p.m. EDT 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, West 75° longitude. (An hour 45 minutes behind our daylight saving time meridian during EDT). To duplicate the star positions on a planisphere you may have to set it to 1 hour 45 minutes earlier than the current time.

September Morning Star Chart

Star Chart for September 2021 (10 p.m. EDT, September 15, 2021). Click on the image to enlarge it. Created using my LookingUp program.

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

• Pointer stars at the front of the bowl of the Big Dipper point to Polaris, the North Star.
• Leaky 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 Limits, Nautical and Astronomical

			EDT
	Morning	Twilight	Evening	Twilight	Dark	Night	Moon
Date	Astro.	Nautical	Nautical	Astro.	Start	End	Illum.
2021-09-01	5h26m	6h04m	21h28m	22h06m	22h06m	1h07m	0.24
2021-09-02	5h28m	6h06m	21h26m	22h04m	22h04m	1h57m	0.16
2021-09-03	5h29m	6h07m	21h24m	22h02m	22h02m	2h55m	0.09
2021-09-04	5h31m	6h08m	21h22m	22h00m	22h00m	4h01m	0.04
2021-09-05	5h32m	6h10m	21h20m	21h57m	21h57m	5h11m	0.01
2021-09-06	5h34m	6h11m	21h18m	21h55m	21h55m	5h34m	0
2021-09-07	5h35m	6h12m	21h16m	21h53m	21h53m	5h35m	0.02
2021-09-08	5h37m	6h14m	21h14m	21h51m	21h51m	5h37m	0.06
2021-09-09	5h38m	6h15m	21h12m	21h49m	21h49m	5h38m	0.13
2021-09-10	5h40m	6h16m	21h10m	21h46m	22h06m	5h40m	0.21
2021-09-11	5h41m	6h18m	21h08m	21h44m	22h35m	5h41m	0.32
2021-09-12	5h43m	6h19m	21h06m	21h42m	23h12m	5h43m	0.43
2021-09-13	5h44m	6h20m	21h04m	21h40m	23h57m	5h44m	0.54
2021-09-14	5h46m	6h22m	21h02m	21h38m	–	5h46m	0.65
2021-09-15	5h47m	6h23m	21h00m	21h36m	0h53m	5h47m	0.76
2021-09-16	5h48m	6h24m	20h58m	21h34m	1h59m	5h48m	0.84
2021-09-17	5h50m	6h25m	20h56m	21h31m	3h10m	5h50m	0.91
2021-09-18	5h51m	6h27m	20h54m	21h29m	4h24m	5h51m	0.96
2021-09-19	5h53m	6h28m	20h52m	21h27m	5h37m	5h53m	0.99
2021-09-20	5h54m	6h29m	20h50m	21h25m	–	–	1
2021-09-21	5h55m	6h31m	20h48m	21h23m	–	–	0.99
2021-09-22	5h57m	6h32m	20h46m	21h21m	–	–	0.95
2021-09-23	5h58m	6h33m	20h44m	21h19m	–	–	0.9
2021-09-24	6h00m	6h34m	20h42m	21h17m	21h17m	21h26m	0.84
2021-09-25	6h01m	6h36m	20h40m	21h15m	21h15m	21h52m	0.76
2021-09-26	6h02m	6h37m	20h38m	21h13m	21h13m	22h23m	0.67
2021-09-27	6h04m	6h38m	20h36m	21h11m	21h11m	23h00m	0.58
2021-09-28	6h05m	6h39m	20h34m	21h09m	21h09m	23h46m	0.49
2021-09-29	6h06m	6h41m	20h32m	21h07m	21h07m	–	0.39
2021-09-30	6h07m	6h42m	20h31m	21h05m	21h05m	0h40m	0.3

Twilight calendar was generated using Cartes du Ciel (Sky Charts).

See my blog post: Twilight Zone for the definitions of the different periods of twilight here: https://bobmoler.wordpress.com/2018/09/27/.

NASA Calendar of Planetary Events

Sep  1  We            Venus: 39.9° E
     1  We   8:23 pm  Moon North Dec.: 25.9° N
     4  Sa  12:07 am  Moon-Beehive: 3.1° S
     5  Su  10:32 am  Venus-Spica: 1.6° N
     6  Mo   8:52 pm  New Moon
     9  Th  10:09 pm  Moon-Venus: 4.1° S
    11  Sa   6:06 am  Moon Perigee: 368500 km
    12  Su  12:35 pm  Moon Descending Node
    13  Mo   4:39 pm  First Quarter
    13  Mo  11:59 pm  Mercury Elongation: 26.8° E
    14  Tu   4:10 am  Neptune Opposition
    14  Tu  11:48 pm  Moon South Dec.: 26° S
    16  Th  10:37 pm  Moon-Saturn: 3.9° N
    18  Sa   2:50 am  Moon-Jupiter: 4.1° N
    20  Mo   7:55 pm  Full Moon, Harvest Moon 
    20  Mo  10:03 pm  Mercury-Spica: 1.4° S
    22  We   3:21 pm  Autumnal Equinox
    26  Su   3:33 am  Moon Ascending Node
    26  Su   5:44 pm  Moon Apogee: 404600 km
    28  Tu   9:57 pm  Last Quarter
    29  We   4:26 am  Moon North Dec.: 26.1° N
Oct  1  Fr            Venus: 44.9° E

All event times are given for UTC-4 hr: Eastern Daylight Saving Time.

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
September, 2021    Local time zone: EDT
+-----------------------------------------------------------------------+
| DATE |  SUN     SUN  DAYLIGHT|   TWILIGHT*    |MOON  RISE OR    ILLUM |
|      |  RISE    SET    HOURS |  END    START  |PHASE SET** TIME FRACTN|
+=======================================================================+
|Wed  1| 07:05a  08:18p  13:13 | 09:25p  05:59a |      Rise 01:57a   25%|
|Thu  2| 07:06a  08:17p  13:10 | 09:23p  06:00a |      Rise 02:55a   17%|
|Fri  3| 07:07a  08:15p  13:07 | 09:21p  06:01a |      Rise 04:01a   10%|
|Sat  4| 07:09a  08:13p  13:04 | 09:18p  06:03a |      Rise 05:11a    5%|
+------+-----------------------+----------------+-----------------------+
|Sun  5| 07:10a  08:11p  13:01 | 09:16p  06:04a |      Rise 06:24a    1%|
|Mon  6| 07:11a  08:09p  12:58 | 09:14p  06:06a |New   Set  08:30p    0%|
|Tue  7| 07:12a  08:07p  12:55 | 09:12p  06:07a |      Set  08:53p    1%|
|Wed  8| 07:13a  08:06p  12:52 | 09:10p  06:08a |      Set  09:16p    5%|
|Thu  9| 07:14a  08:04p  12:49 | 09:08p  06:10a |      Set  09:40p   11%|
|Fri 10| 07:16a  08:02p  12:46 | 09:06p  06:11a |      Set  10:05p   19%|
|Sat 11| 07:17a  08:00p  12:43 | 09:04p  06:12a |      Set  10:35p   29%|
+------+-----------------------+----------------+-----------------------+
|Sun 12| 07:18a  07:58p  12:40 | 09:02p  06:13a |      Set  11:12p   40%|
|Mon 13| 07:19a  07:56p  12:37 | 09:00p  06:15a |F Qtr Set  11:57p   52%|
|Tue 14| 07:20a  07:54p  12:33 | 08:58p  06:16a |      Set  12:53a   63%|
|Wed 15| 07:21a  07:52p  12:30 | 08:56p  06:17a |      Set  01:59a   73%|
|Thu 16| 07:23a  07:51p  12:27 | 08:54p  06:19a |      Set  03:10a   82%|
|Fri 17| 07:24a  07:49p  12:24 | 08:52p  06:20a |      Set  04:24a   90%|
|Sat 18| 07:25a  07:47p  12:21 | 08:50p  06:21a |      Set  05:37a   95%|
+------+-----------------------+----------------+-----------------------+
|Sun 19| 07:26a  07:45p  12:18 | 08:48p  06:23a |      Set  06:47a   99%|
|Mon 20| 07:27a  07:43p  12:15 | 08:46p  06:24a |Full  Rise 08:03p  100%|
|Tue 21| 07:29a  07:41p  12:12 | 08:44p  06:25a |      Rise 08:23p   99%|
|Wed 22| 07:30a  07:39p  12:09 | 08:42p  06:26a |      Rise 08:43p   96%|
|Thu 23| 07:31a  07:37p  12:06 | 08:40p  06:28a |      Rise 09:03p   91%|
|Fri 24| 07:32a  07:35p  12:03 | 08:39p  06:29a |      Rise 09:26p   85%|
|Sat 25| 07:33a  07:33p  12:00 | 08:37p  06:30a |      Rise 09:52p   78%|
+------+-----------------------+----------------+-----------------------+
|Sun 26| 07:35a  07:32p  11:57 | 08:35p  06:31a |      Rise 10:23p   69%|
|Mon 27| 07:36a  07:30p  11:53 | 08:33p  06:33a |      Rise 11:00p   60%|
|Tue 28| 07:37a  07:28p  11:50 | 08:31p  06:34a |L Qtr Rise 11:46p   51%|
|Wed 29| 07:38a  07:26p  11:47 | 08:29p  06:35a |      Rise 12:40a   41%|
|Thu 30| 07:39a  07:24p  11:44 | 08:27p  06:36a |      Rise 01:42a   32%|
+-----------------------------------------------------------------------+
* Nautical Twilight
** Moonrise or moonset, whichever occurs between sunrise and sunset

Generated using my LookingUp for DOS program.