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02/27/2020 – Ephemeris – Saturday is the intercalary day

February 27, 2020 Comments off

Ephemeris for Thursday, February 27th. Today the Sun will be up for 11 hours and 2 minutes, setting at 6:27, and it will rise tomorrow at 7:22. The Moon, half way from new to first quarter, will set at 10:28 this evening.

Saturday we’re going to have one of those special days that only occur once every 4 years making this a leap year. It’s the intercalary day that compensates for the fact that the earth takes 365 and nearly a quarter day to orbit the Sun. That orbit is a year, and those quarter days are accumulated and added as the last day of February on years divisible by 4. The Gregorian reform makes a slight adjustment on most century years, making century years not divisible by 400 ordinary years to keep the calendar in sync with the seasons. The Romans, from who we’ve gotten our calendar considered the month of February as unlucky, and so they shortened it. Enjoy your extra day on Saturday.

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

 

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.