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01/07/2020 – Ephemeris – What the heck is an ephemeris? Plus my Betelgeuse update

January 7, 2020 Comments off

Ephemeris for Tuesday, January 7th. Today the Sun will be up for 8 hours and 58 minutes, setting at 5:18, and it will rise tomorrow at 8:19. The Moon, 3 days before full, will set at 6:09 tomorrow morning.

What the heck is an ephemeris? According to Wikipedia: “In astronomy and celestial navigation, an ephemeris (plural: ephemerides; from Latin ephemeris, meaning ‘diary’, from the Greek,… meaning ‘diary, <or> journal’) gives the positions of… astronomical objects… at a given time or times. Historically, positions were given as printed tables of values, given at regular intervals of date and time.” My tables are now databases which I generate for the year during the prior December from published algorithms. I will show all on my blog today: It’s at bobmoler<dot>wordpress<dot>com. (You are already here) I used to have to interpolate values from printed ephemerides for the first 5 or so years.

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

Addenda

An Ephemeris Example

Ephemeris for 2I/Borisov

Here’s an ephemeris for the Interstellar comet for 2I/Borisov AKA C/2019 Q4 (Borisov) from the Jet Propulsion Laboratory’s (JPL) Horizons system.

R.A. is right ascension – East-west position in the sky, like longitude on the Earth, only it’s in hours, minutes and seconds.  One hour = 15 degrees.

DEC is declination – North-south position, in the sky, exactly like latitude on the Earth in degrees, minutes and seconds.

J2000.0 means that the above coordinates are based on where the vernal equinox point in the sky was on January 1, 12:00 Terrestrial Time, 2000.  Or January 1, 2000, 11:58:55.816 UTC as reported in Wikipedia.

APmag – Apparent visual magnitude.  Magnitudes are like golf scores.  The higher magnitude the dimmer the object.  It’s really, really dim.

delta – Distance from the Earth in terms of Astronomical Units (AU).  1 AU is Earth’s mean distance from the Sun.

deldot – The change in delta.  It’s in kilometers per second.  If positive, it’s going away.

For more information on how I produce ephemerides for this program go here: https://bobmoler.wordpress.com/2019/01/22/

The dimming of Betelgeuse

I finally got a clear evening.  However snow and freezing rain the rest of the week.

Orion at 7:07 p.m. January 6, 2020

Betelgeuse in Orion at 7:07 p.m. January 6, 2020. Taken with my Samsung Galaxy S10+ in the moonlight. Compare the brightness of Betelgeuse with Rigel, Bellatrix and the belt stars.

Orion's brightest stars

Orion’s brightest stars with their names for 9 p.m. January 7, 2019. Click on the image to make Orion a giant hunter. Created using Stellarium.

See last Thursday’s post on the dimming of Betelgeuse: https://bobmoler.wordpress.com/2020/01/02/

01/06/2020 – Ephemeris – The Earth was closest to the Sun in its orbit yesterday

January 6, 2020 Comments off

Ephemeris for Monday, January 6th. Today the Sun will be up for 8 hours and 57 minutes, setting at 5:17, and it will rise tomorrow at 8:19. The Moon, half way from first quarter to full, will set at 5:02 tomorrow morning.

Yesterday’s perihelion, or closest point of the Earth to the Sun of roughly 91.4 million miles (147 million km) is only 1.7% closer to the Sun than average. It doesn’t do much to make our winters warmer, but it does make winter the shortest season. That’s because the Earth travels faster when near the Sun than when it’s farther away. Winter lasts only 89 ½ days. The Earth’s aphelion, when it’s farthest from the Sun will be on the 4th of July, in summer, making that the longest season at 93 ½ days. Of course being this far north it feels like winter is longer than summer, but astronomically it’s the other way around. Being a leap year, with February having 29 days, spring will arrive a calendar day early on the 19th of March.

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

Addendum

Earth's orbit

The Earth’s orbit, somewhat exaggerated, showing perihelion and the seasons. Credit “Starts with a Bang” blog by Ethan Siegel.

Seasons for 2020

The Seasons for 2020 from data in Astronomical Tables of the Sun, Moon, and Planets Third Edition by Jean Meeus. Date and times are in TD, Dynamical Time. Subtract about 1 minutes to convert to Universal Time (UT).  Also subtract 5 hours for Eastern Standard Time and 4 hours for Eastern Daylight Time.

For and explanation of the Cross-Quarter Days column, check out my Ground Hog Day post last year:  https://bobmoler.wordpress.com/2019/02/02/02-02-2019-ephemeris-extra-groundhog-day-and-other-seasonal-days/

 

04/19/2019 – Ephemeris – Why Sunday is Easter

April 19, 2019 Comments off

Ephemeris for Good Friday, Friday, April 19th. Today the Sun will be up for 13 hours and 40 minutes, setting at 8:32, and it will rise tomorrow at 6:50. The Moon, at full today, will rise at 8:56 this evening.

Easter will be celebrated by western Christian churches this Sunday. Easter is a movable feast in that it falls on a different date each year following the first full moon of spring. It’s an attempt to follow the Jewish Passover, which starts on the 15th of the month of Nisan. Being a lunar calendar the 15th the generally the night of the full moon. And since the Last Supper was a Seder, the Christian church wanted to follow Passover as closely as possible using the Roman solar based (Julian*) calendar where the year was 365.25 days long. Passover starts at sunset tonight. The western churches eventually adopted the Gregorian calendar to keep in sync with the seasons. The Eastern churches kept the old Julian Calendar and other considerations to calculate the date of Easter, which arrives a week later.

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

* The Julian calendar is named after Julius Caesar who proposed it in 46 BC.  It took effect on January 1, 45 BC.  By the Julian calendar today is April 6.

03/18/2019 – Ephemeris – Spring, the full moon and Easter

March 18, 2019 Comments off

Ephemeris for Monday, March 18th. Today the Sun will be up for 12 hours and 2 minutes, setting at 7:52, and it will rise tomorrow at 7:48. The Moon, 2 days before full, will set at 7:21 tomorrow morning.

Spring is two days away. In checking my astronomical calendars I noticed an odd thing related to the date of Easter for western churches. If I said that the date of Easter was the first Sunday after the first full Moon after the vernal equinox. I’d be wrong. Even if I replaced vernal equinox with first day of spring, I would still be wrong by ecclesiastical standards. The ecclesiastical vernal equinox is March 21st, no matter what. Plus the full moon date is a tabulated value and not necessarily the astronomical full moon date. This year the astronomical first full moon of spring falls less than 4 hours after the astronomical vernal equinox on March 20th. Therefore Easter will be late this year on April 21st, 4 days earlier than its latest possible date.

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

01/22/2019 – Ephemeris – What the heck is an ephemeris?

January 22, 2019 Comments off

Ephemeris for Tuesday, January 22nd. Today the Sun will be up for 9 hours and 25 minutes, setting at 5:37, and it will rise tomorrow at 8:11. The Moon, 1 day past full, will rise at 7:41 this evening.

What the heck is an ephemeris? According to Wikipedia: “In astronomy and celestial navigation, an ephemeris (plural: ephemerides; from Latin ephemeris, meaning ‘diary’, from the Greek,… meaning ‘diary, <or> journal’) gives the positions of… astronomical objects… at a given time or times. Historically, positions were given as printed tables of values, given at regular intervals of date and time.” My tables are now databases which I generate for the year during the prior December from published algorithms. I will show all on my blog today: It’s at bobmoler.wordpress.com. (You are already here)  I used to have to interpolate values from printed ephemerides.

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

Addendum

An ephemeris

Here are sections of an ephemeris of the positions of 2014 MU69, Ultima Thule that the New Horizons flew past on New Years day. Created by JPL’s Horizons web site.

R.A. is right ascension – East-west position in the sky, like longitude on the Earth, only it’s in hours, minutes and seconds.  One hour = 15 degrees.

DEC is declination – North-south position, in the sky, exactly like latitude on the Earth in degrees, minutes and seconds.

J2000.0 means that the above coordinates are based on where the vernal equinox point in the sky was on January 1, 12:00 Terrestrial Time, 2000.  Or January 1, 2000, 11:58:55.816 UTC as reported in Wikipedia.

APmag – Apparent visual magnitude.  Magnitudes are like golf scores.  The higher magnitude the dimmer the object.  It’s really, really, really dim.

delta – Distance from the Earth in terms of Astronomical Units (AU).  1 AU is Earth’s mean distance from the Sun.

deldot – The change in delta.  Note that is negative.  5 days after New Horizons passed Ultima Thule that spacecraft and Ultima Thule passed behind the Sun.  Now the Earth in its orbit is approaching Ultima as we are coming around the Sun.

How my data is created

LU for DOS

I use my LookingUp for DOS program to generate sunrise/sunset, moonrise/moonset tables for the year.  I also create planetary ephemeris tables here.

Almanac Master

My Ephemeris Helper program massages the raw data from the above program to create this Almanac Master table.

Intro creation

The first 15 or so seconds of the Ephemeris program is created by the Ephemeris Helper program from the Almanac Master, a Holiday Table, A One Time Event Table created from NASA’s SKYCAL Calendar Table, and Reoccurring Events Table.

Planet Master table

The Planet Master table in the Ephemeris Helper program which I use each Wednesday for planet positions.

LookingUp for Windows

First tab of the LookingUp for Windows program which I don’t use much for the radio program but has uses on this blog and for illustrations for the Stellar Sentinel, the newsletter for the Grand Traverse Astronomical Society, that I edit, which is sent to members and distributed free via email to educators.

Source for the algorithms that I use is Astronomical Algorithms by Jean Meeus, Willmann-Bell 1991.

 

 

 

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

January 15, 2019 Comments off

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:

Calendar excerpts

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.

 

05/01/2018 – Ephemeris – Previewing May Skies

May 1, 2018 Comments off

Ephemeris for Tuesday, the first day of May. The Sun rises at 6:32. It’ll be up for 14 hours and 15 minutes, setting at 8:47. The Moon, 2 days past full, will rise at 10:32 this evening.

They say April showers bring May flowers, but I don’t think they meant snow showers. Daylight hours in the Interlochen/Traverse City area will increase from 14 hours and 15 minutes today to 15 hours 19 minutes on May 31st. The altitude, or angle, of the sun above the southern horizon at local noon will ascend from 60 degrees today to 67 degrees at month’s end. The altitude of the sun in the Straits area will be a degree lower than that but your length of daylight will be a few minutes longer. Local apparent noon this month, when the sun passes due south, will be about 1:38 p.m. The Eta Aquariid meteor shower will reach its peak about 3 a.m. this Saturday morning the 5th, but the bright morning Moon will interfere.

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

Addendum

May Evening Sky Chart

May evening star chart

Star Chart for May 2018 (11 p.m. EDT May 15, 2018). Created using my LookingUp program. Click on image to enlarge.

The planets and stars are plotted for the 15th at 11 p.m. EDT in the evening and 5 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.

Note the chart times of 11 p.m. and 5 a.m. are for the 15th. For each week before the 15th add ½ hour (28 minutes if you’re picky). 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.

May Morning Star Chart

May Morning Star Chart

Star Chart for May 2018 mornings based on 5 a.m. May 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 and
  • Continue with a spike to Spica.
  • The Summer Triangle is in red.
  • EAqr is the Eta Aquariid meteor shower radiant.  This shower will be plagued by a waning gibbous moon. It will be addressed in the May 3rd program.  This is a shower of bits from Halley’s Comet.

Twilight

Evening nautical twilight ends at 10:02 p.m. EDT on the 1st, increasing to 10:44 p.m. EDT on the 31st.
Evening astronomical twilight ends at 10:46 p.m. EDT on the 1st, increasing to 11:42 p.m. EDT on the 31st.
Morning astronomical twilight starts at 4:40 a.m. EDT on the 1st, and decreasing to 3:45 a.m. EDT on the 31st.
Morning nautical twilight starts at 5:25 a.m. EDT on the 1st, and decreasing to 4:44 a.m. EDT on the 31st.

NASA Calendar of Planetary Events

    Date    Time    Event
May 01  Tu          Venus: 27.2° E
    02  We  9:24 am Venus-Aldebaran: 6.4° N
    04  Fr  4:31 pm Moon-Saturn: 1.9° S
    04  Fr  7:00 pm Moon South Dec.: 20.6° S
    05  Sa  3:03 am Eta Aquarid Shower: ZHR = 60
    05  Sa  8:35 pm Moon Apogee: 404500 km
    06  Su  3:24 am Moon-Mars: 3° S
    07  Mo  6:24 am Moon Descending Node
    07  Mo 10:09 pm Last Quarter
    08  Tu  8:10 pm Jupiter Opposition
    13  Su  1:21 pm Moon-Mercury: 2.5° N
    15  Tu  7:48 am New Moon
    17  Th  2:11 pm Moon-Venus: 4.8° N
    17  Th  5:06 pm Moon Perigee: 363800 km
    18  Fr 11:02 am Moon North Dec.: 20.7° N
    20  Su  7:57 am Moon-Beehive: 1.7° N
    20  Su  9:13 am Moon Ascending Node
    21  Mo  8:53 pm Moon-Regulus: 1.5° S
    21  Mo 11:49 pm First Quarter
    27  Su  1:39 pm Moon-Jupiter: 4.3° S
    29  Tu 10:20 am Full Moon
    31  Th  9:20 pm Moon-Saturn: 1.8° S
Jun 01  Fr          Venus: 34.5° 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
     May, 2018    Local time zone: EDT
     +-----------------------------------------------------------------------+
     | DATE |  SUN     SUN  DAYLIGHT|   TWILIGHT*    |MOON  RISE OR    ILLUM |
     |      |  RISE    SET    HOURS |  END    START  |PHASE SET** TIME FRACTN|
     +=======================================================================+
     |Tue  1| 06:32a  08:47p  14:15 | 10:00p  05:20a |      Rise 10:32p   96%|
     |Wed  2| 06:31a  08:49p  14:17 | 10:01p  05:18a |      Rise 11:31p   91%|
     |Thu  3| 06:29a  08:50p  14:20 | 10:03p  05:17a |      Rise 12:26a   85%|
     |Fri  4| 06:28a  08:51p  14:23 | 10:04p  05:15a |      Rise 01:15a   78%|
     |Sat  5| 06:27a  08:52p  14:25 | 10:06p  05:13a |      Rise 02:00a   69%|
     +------+-----------------------+----------------+-----------------------+
     |Sun  6| 06:25a  08:53p  14:28 | 10:07p  05:12a |      Rise 02:39a   60%|
     |Mon  7| 06:24a  08:55p  14:30 | 10:09p  05:10a |L Qtr Rise 03:14a   51%|
     |Tue  8| 06:23a  08:56p  14:33 | 10:11p  05:08a |      Rise 03:45a   41%|
     |Wed  9| 06:21a  08:57p  14:35 | 10:12p  05:06a |      Rise 04:14a   32%|
     |Thu 10| 06:20a  08:58p  14:38 | 10:14p  05:05a |      Rise 04:42a   23%|
     |Fri 11| 06:19a  08:59p  14:40 | 10:15p  05:03a |      Rise 05:09a   15%|
     |Sat 12| 06:18a  09:00p  14:42 | 10:17p  05:02a |      Rise 05:38a    8%|
     +------+-----------------------+----------------+-----------------------+
     |Sun 13| 06:16a  09:02p  14:45 | 10:18p  05:00a |      Rise 06:09a    3%|
     |Mon 14| 06:15a  09:03p  14:47 | 10:20p  04:59a |      Rise 06:45a    1%|
     |Tue 15| 06:14a  09:04p  14:49 | 10:21p  04:57a |New   Set  09:20p    1%|
     |Wed 16| 06:13a  09:05p  14:52 | 10:23p  04:56a |      Set  10:32p    3%|
     |Thu 17| 06:12a  09:06p  14:54 | 10:24p  04:54a |      Set  11:40p    9%|
     |Fri 18| 06:11a  09:07p  14:56 | 10:26p  04:53a |      Set  12:41a   17%|
     |Sat 19| 06:10a  09:08p  14:58 | 10:27p  04:51a |      Set  01:33a   26%|
     +------+-----------------------+----------------+-----------------------+
     |Sun 20| 06:09a  09:09p  15:00 | 10:29p  04:50a |      Set  02:17a   37%|
     |Mon 21| 06:08a  09:10p  15:02 | 10:30p  04:49a |F Qtr Set  02:55a   48%|
     |Tue 22| 06:07a  09:12p  15:04 | 10:32p  04:47a |      Set  03:27a   59%|
     |Wed 23| 06:06a  09:13p  15:06 | 10:33p  04:46a |      Set  03:56a   70%|
     |Thu 24| 06:05a  09:14p  15:08 | 10:34p  04:45a |      Set  04:24a   79%|
     |Fri 25| 06:05a  09:15p  15:09 | 10:36p  04:44a |      Set  04:52a   87%|
     |Sat 26| 06:04a  09:16p  15:11 | 10:37p  04:43a |      Set  05:20a   93%|
     +------+-----------------------+----------------+-----------------------+
     |Sun 27| 06:03a  09:16p  15:13 | 10:38p  04:42a |      Set  05:51a   97%|
     |Mon 28| 06:02a  09:17p  15:15 | 10:39p  04:41a |      Set  06:24a   99%|
     |Tue 29| 06:02a  09:18p  15:16 | 10:41p  04:40a |Full  Rise 09:21p  100%|
     |Wed 30| 06:01a  09:19p  15:18 | 10:42p  04:39a |      Rise 10:18p   98%|
     |Thu 31| 06:00a  09:20p  15:19 | 10:43p  04:38a |      Rise 11:10p   95%|
     +-----------------------------------------------------------------------+
     * Nautical Twilight
     ** Moonrise or moonset, whichever occurs between sunset and sunrise