Notes by George Gladfelter
Changes may be shown in green or blue.
Meteor Shower Calendar (Best viewing after midnight looking east. Dates vary from year to year.)
Dates (maximum) Shower Name
Jan 1-5 (3-4) Quadrantids
Jan 15 - Feb 8 (7-8) Alpha Aurigids
Apr 19-24 (22) April Lyrids
May 1-12 (5) Eta Aquarids
June 10-21 (15) June Lyrids
Jul 15 - Aug 15 (28) Delta Aquarids
Aug 1-18 (12) Perseids
Oct 17-26 (20) Orionids
Nov 14-20 (17) Leonids
Dec 4-16 (13-14) Geminids
Click here for the data (world wide) on moon phases,
solar and lunar eclipses, equinoxes and solstices, lunar perigee and apogee,
lunar perihelion and aphelion, and various data for Mercury, Venus, Mars,
Jupiter, and Saturn for 2023-2024. Also available are detailed data on
solar eclipses for 2023-2024.
Note: Copies of previous editions should be discarded.
2. Click here for ephemerides for the Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune. For 2023, the apparent right ascension, declination, distance, and visual magnitude are listed for each day in the year at zero hours Terrestrial Dynamical Time (TT) . For objects other than the Sun, the angle of separation from the Sun is also listed. For the planets, the visual magnitude is also listed for the planet only (not including any rings).
3. Click here for revised sunrise, sunset, and twilight times at the Journey Museum and Learning Center (JMLC) for 2023-2026. For an explanation of the table, click here.
4. Click here for times of moonrise, moonset, and transits of the moon (as seen from JMLC) and also the percentage of the moon's disk that is illuminated, and the Moon's declination, at 9 PM MST for 2020-2024. Note: rising and setting times of any celestial object are subject to uncertainty due to topography, and especially variations in atmospheric refraction. Also, the calculations are specific to a single location and cannot be easily adapted to locations more than a few miles away; therefore, treat the tabulated times for rising and setting as approximations. The other times listed are not affected by refraction, but are specific to the observer's longitude or position. Only phenomena that will be visible (assuming no clouds) are listed.
5. The planets are best placed for observing from the Earth when the angle from Sun to Earth to object is greatest. For Mercury and Venus this is the time of greatest separation or elongation (they are not exactly the same), and for the others the time called opposition (this is the time when the planet's right ascension is 180 degrees away from the Sun's). For a table of these times for 2018-2050 click here.
6. Click here for a table showing data at dusk, the middle of the night, and dawn for the sun, moon, and the five bright planets for each night 2020-2023. If the moon, or a planet, is within five degrees of a planet, another line of data shows the visual separation of the pair. Click here for an explanation of the table. Also, click here for times of rising, setting, and transit (marked "r", "s", or "t") of the sun, moon, and bright planets in 2020-2023. Included are the times for morning and evening twilight (mt and et), the four phases of the moon, and the seasons (ME = March Equinox, JS = June Solstice, SE = September Equinox, DS = December Solstice). Note: the rising and setting times are for the center of the sun, moon, or planet without correcting to the upper limb of the object; the twilight times are for when the sun is 15 degrees below the horizon - this is intermediate between nautical and astronomical twilight. Note well - this file is close to 150 pages long.
7. Click here for a table listing the transit times of twenty stars, as seen from JMLC, for 2022-2023. These data can be used easily to calculate approximate rising and setting times. Click here for an explanation of the table. Click here for a list of bright stars with their coordinates for mid-2023.
8. Click here for dates and times of Transits of Mercury 2016-2100.
9. Click here for a list (2022-2024) of Lunar Occultations of (A) bright planets and (B) certain bright stars (magnitude 3.5 and brighter), and (C) solar eclipses. When appropriate, data for observers at the Journey Museum in Rapid City are shown. revised 06/22/2022. Click here for a listing of all solar eclipses for 2014-2040.
10. Posted here is a text file giving the coefficients for apparent Right Ascension, Declination, Distance, and Horizontal Parallax of the Moon for 2021-2022. The distance is the true distance (light time not factored in) in kilometers. The angular coordinates are in degrees. Each quantity is to be computed as:
quantity = A0 + A1x + A2x2 + ... + A5x5
where x = h/24 with h = time (TT) in hours
thus, 0.0 <= x < +1.0.
The results for the angular quantities should agree very closely with the tabulated values in the Astronomical Almanac, and the distance should be consistent within a few meters.
For the years1990-2020, click here. For 2023-2050, click here.
11. Posted here is a text file listing DUT1 (DUT1 = TT - UT1) and DUTC (DUTC = TT-UTC) for the first of each month, starting with 1972. The table extends 12 months into the future using predictions by IERS, and a few years beyond that by extrapolation. Observable events whose timing depends on the observer's location (such as eclipses of the Sun, stars, and planets) typically also depend on the Earth's rotational angle, and therefore on DUTC and/or DUT1.
12. For 2022-2024, astronomical phenomena are listed below with an emphasis on those events that will be visible from western South Dakota. Note: lunar occultations are listed below only if visible from JMLC.
The Islamic dates listed below are tabular and may vary from observation at any particular location.
Distances to the Moon, Sun, or a planet are for Earth-center to object-center.
01/02&03 - 07:27:54 MST - Latest sunrise at JMLC
01/04 - 09:18 MST - Earth closest to the Sun (0.98330 au)
01/14 - Year 2776 Ab Urbe Condita starts (Roman/Julian calendar)
01/22 (Sunday) - Chinese New Year (year of the Rabbit) - see notes
01/29 - 23h MST - Mercury at greatest elongation, 25.0deg. W.
03/12 - MDT in effect
03/20 15:24 MDT - Spring Equinox
03/22 evening - Ramadanstarts
04/05 evening - Passover
04/09 - Easter Sunday
04/11 - 16h MDT - Mercury at greatest elongation 19.5° E.
04/16 - Orthodox Easter
04/19 - a partial solar eclipse starts at 19:34 MDT, becomes an annular eclipse from 20:37:06, a total eclipse at 20:37:17, reaches the mid-point at 22:16:46, again becomes annular at 23:55:31, becomes partial at 23:56:40, and ends at 24:59:20, but from JMLC, and nearby, none of the sun's disk will be obscured. Best observer's position: 9.61 S, 125.77 E, magnitude 1.007.
04/21 evening - Eid ul-Fitr
05/05 - a Partial Penumbral Lunar Eclipse occurs from 09:14 to 13:31 MDT. The Moon will not be visible from the USA during this time.
05/28 23h MDT - Mercury at greatest elongation 24.9° W.
06/04 - 5h MDT - Venus at greatest elongation 45.4° E.
06/15 - 05:09:05 MDT - Earliest sunrise at JMLC
06/21 08:58 MDT - Summer Solstice, longest day of the year at JMLC: 15h 30m
06/26&27 - 20:40:15 MDT - Latest sunset at JMLC
07/06 13h MDT - Earth farthest from the Sun (1.01668 au)
07/18 evening - Year 1445 Anno Hegira starts (Islamic)
08/09 19h MDT - Mercury at greatest elongation 27.4° E.
08/24 A lunar occultation of the star Antares (mag. 1.06) will begin, for observers at the Journey Museum, at 19:59:37.9 MDT and end at 21:11:41.4.
08/27 1h MDT - Saturn at opposition
08/27 5h MDT - Saturn appears closest to Earth (8.7630 au)
09/15 evening - Year 5784 Anno Mundi starts (Jewish)
09/22 - 7h MDT - Mercury at greatest elongation 17.9° W.
09/23 00:50 MDT - Fall Equinox
09/24 evening - Yom Kippur (Jewish)
10/14 - An annular solar eclipse occurs, but will be visible from anywhere near here as only a partial eclipse . The best view will be at 12:00 MDT as seen from 11.36 N, 83.10 W., magnitude 0.9764. From JMLC, the eclipse will be seen as a partial eclipse from 9:17:04 MDT until 12:02:32 with 64% of the Sun being blocked by the Moon at 10:36:33.
10/23 - 17h MDT - Venus at greatest elongation 46.4° W.
11/01 15h MDT - Jupiter appears closest to Earth (3.9824 au)
11/02 23h MDT - Jupiter at opposition
11/05 - MST returns
12/04 7h MDT - Mercury at greatest elongation 21.3° E.
12/07 evening- Hanukkah (Jewish)
12/09 - 16:14:25 MST - Earliest sunset at JMLC
12/21 20:27 MST - Winter Solstice- Shortest day of the year at JMLC: 8h 52m 45s.
Planets: Also see notes, below. Dates, in this section, mostly refer to the date on which the night starts, "midnight" means the middle of the night, not always 12:00 A.M. For events at "midnight" the date refers to the start of the night in question. Dates associated with dawn or morning only are not referenced to the previous night. The data given here are valid for observers in western South Dakota.
Pairings, within 5 degrees: 01/03 - the Moon and Mercury 4.2° at dusk, 01/08 - Mercury and Saturn (5.0 deg) begin a series at dusk, they grow closest on January 12 and 13 (3.4 deg) and end 01/16; 01/29 - the Moon and Mars 3.2° at dawn, 02/02 - the Moon and Jupiter 4.5° at dusk, 02/27 - the Moon and Mars 4.9° at dawn, 03/01 - Venus and Mars are 5° apart in the pre-dawn sky with the separation down to 3.9 degrees on 03/13 to 03/18 then widening out for a few days, 03/25 - Venus and Saturn 3.9° at dawn converging to 2.1° on the 28th and 29th then diverging to 4.8° by 04/02, 03/31 - Venus, Mars, and Saturn within 3.2° of each other; 04/05 - Mars and Saturn 0.4° at dawn then 5.0° on the 12th, 04/25 - Venus and Jupiter 5.0° at dawn closing to 0.4° on the 30th and widening to 4.3° on 05/05, 05/21 - Mars and Jupiter 4.6° at dawn closing to 0.6° on the 29th then 4.7° on 06/06, 06/21 - the Moon and Jupiter 4.3° at dawn, 06/22 - the Moon and Mars 4.4° at dawn, 06/26 - the Moon and Venus 2.9° at dawn, 06/27 - the Moon and Mercury 3.8° at dawn, 07/18 - the Moon and Jupiter 3.8° at midnight, 07/20 - The Moon and Mars 4.0° at midnight closing to 2.3° at dawn, 07/26 - the Moon and Venus 3.7° at dawn, 08/11 - the Moon and Saturn under 5° most of the night, 08/14 - the Moon and Jupiter about 3° most of the night, 08/18 - the Moon and Mars 2.2 deg, 09/11 - the Moon and Jupiter 4.1° at dawn, 09/16 - the Moon and Mars 4.7° at midnight, 10/08 - the Moon and Jupiter 4.2° at dusk, 10/14 - the Moon and Mars 3.7° at midnight, 10/24 - the Moon and Mercury 0.7° at dawn - but barely above the Eastern horizon, 11/01 - the Moon and Saturn 4.9° at dusk, 11/04 - the Moon and Jupiter 3.3° at dusk and 4.8° at midnight, 11/10 - the Moon and Mars 3.7° at midnight then 2.2° at dawn, 12/01 - the Moon and Jupiter 3.5° at dusk then 2.8° at midnight, 12/07 - the Moon and Mars 1.8° at dusk, 1.3° at midnight then 4.2° at dawn, 12/22 - Mercury and Venus 5° at dusk closing to 1.4° on the 28th then 3.7° on January first, 12/24 - the Moon and Mercury 4.9° at dusk (with Venus also near),
Mercury: Mercury can only be seen when it is sufficiently high in the sky before sunrise or after sunset. Its appearances typically last only a few days at a time. On 01/01 it is low in the sky and chasing the setting Sun in the evening sky. By the 01/12 it becomes a dim object appearing in the morning sky just before sunrise. By 01/22 and 01/23 it is at its highest point for this apparition and has brightened to magnitude 0.0 after which it continues to brighten, but appears lower in the sky on successive mornings, sinking out of sight by around 02/13. Mercury reappears as a bright magnitude -1.4 evening object (and near Jupiter for three evenings) on 03/26. By 04/11 it will be as high as it will get for this apparition, but will then be dimmer at magnitude 0.0 as it continues to get lower and dimmer toward the end of the apparition around 04/24. Mercury will briefly make an appearance as a morning object low in the ENE sky from 06/02 to 06/11. It will reappear around 07/15 as an evening object around 07/15, rising higher (but losing some brightness) until around 07/28 and will then sink out of view around 08/10. As a morning object it will reappear around 09/12 as a dim magnitude 2.6 object in the morning getting higher and brighter until 09/22 (magnitude -9.5) and then while still gaining brightness sink back into the Sun's glare around 10/07. On about 11/26 it begins its last evening apparition of the year as a bright object that never gets very high, peaks around 12/08, and ends its show around 12/15. On 12/27 a morning apparition will start and extend into 2024.
Venus starts the year as an evening object low on the horizon, rising higher day by day until reaching its highest point around 04/30, and sinking back into the Sun's glare around 07/22. It becomes a bright morning object around 08/23, peaking around 10/21, then continues its show into 2024 while losing altitude.
Mars starts the year as an evening object at magnitude -1.2 and sets before sunrise. It slowly loses a little brightness each day until by early May it sets before the middle of the night and has dimmed to magnitude 1.4. It then continues to sink lower against the western horizon night after night until early September when it has dimmed to magnitude 1.7 or so and is seen only briefly after sunset and is done for the year.
Jupiter starts the year as an evening object until it sets soon after the Sun by late March. Jupiter becomes a morning object in mid-May. It is best on the night of 11/02 at magnitude -2.9 and is then an all-night object. It finishes the year as a bright evening object.
Saturn starts the year as an evening object (magnitude 0.8) until early February. It then reappears as a morning object around 03/18. By the night of 08/27 it is an all-night object at magnitude 0.4, and thereafter becomes an evening object for the rest of the year.
Full Moon Nights: 01/05, 02/04-05, 03/06, 04/05, 05/04, 06/03, 07/02, 07/31, 08/30, 09/28, 10/27-28, 11/26, 12/26. (See notes below.)
2024Note: Previous editions of this section (up the information on viewing planets) were full of inadvertent errors
01/03 - 07:27:54 MST - Latest sunrise at JMLC
01/02 - 17:38 MST - Earth closest to the Sun (0.9833 au)
01/08 - 06:47:12.8 - Antares, as seen at JMLC, will be eclipsed by the Moon; but the Sun will rise before the star reemerges.
01/12 - 08h MST - Mercury at greatest elongation, 23.5 deg. W.
01/14 - Year 2777Ab Urbe Condita starts (Roman/Julian calendar)
02/10 (Saturday) - Chinese New Year (year of the Dragon) - see notes
02/14 - Ash Wednesday
03/10 - MDT in effect
03/10 evening - Ramadan begins
03/19 21:06 MDT - Spring Equinox
03/24 17h - Mercury greatest elongation, 18.7 deg. E.
03/25 01:13 - From about 2 hours before to 2 hours after a partial penumbral lunar eclipse will be in progress, but will be too faint to impress observers on Earth.
03/31 - Easter Sunday
04/08 - A partial solar eclipse will last from 09:42 to 14:52; it will be total from 11:39 to 13:59; but from JMLC it will appear as a partial eclipse from 11:39 to 13:58 and maximum obscuration will be 58% at 12:48:27.
04/09 evening - Eid ul-Fitr
04/22 evening - Passover
05/05 - Orthodox Easter
05/10 - 15h MDT - Mercury at greatest elongation 26.4 deg. W.
06/14&15 - 05:09:05 MDT - Earliest sunrise at JMLC
06/20 14:51 MDT - Summer Solstice, longest day of the year at JMLC: 15h 30m
06/25&26 - 20:40:13 MDT - Latest sunset at JMLC
07/04 23h MDT - Earth farthest from the Sun (1.0167 au)
07/07 evening - Year 1446Anno Hegira starts (Islamic)
07/13 - As seen from JMLC, Spica will be eclipsed by the Moon from 20:44:34.2 MDT until 22:04:24.7
07/22 01h MDT - Mercury at greatest elongation 26.9 deg. E.
09/04 121h MDT - Mercury at greatest elongation 18.1 deg. W.
08/24 A lunar occultation of the star Antares (mag. 1.06) will begin, for observers at the Journey Museum, at 19:59:36.6 MDT and end at 21:11:40.2.
09/07 23h MDT - Saturn at opposition
09/08 1h MDT - Saturn appears closest to Earth (8.658 au)
09/17 - As seen from JMLC, Saturn will be eclipsed by the Moon; first contact at 05:13:15.6 MDT, total blockage by 05:13:47.4, but Saturn will set before emerging from behind the Moon.
09/17 - A partial lunar eclipse: first contact 18:41, umbral phase at 20:12, max (4% in umbra) at 20:44, umbral phase ends at 21:17, last contact at 22:47. Note: first and last contact with the penumbra are not detectable from the Earth.
09/22 06:44 MDT - Fall Equinox
10/02 - A solar eclipse. Globally: at 09:43 MDT it starts as a partial eclipse, 10:51 becomes annular, 12:45 mid-point at 114.515 W. 21.953 S. magnitude 0.9667, 14:39 reverts to partial, 15:47 ends. For observer at JMLC: no obscuration of the Sun by the Moon will be seen.
10/02 evening - Year 5785 Anno Mundi starts (Jewish)
10/11 evening - Yom Kippur (Jewish)
10/14 - An annular solar eclipse occurs, but will be visible from anywhere near here as only a partial eclipse . The best view will be at 11:59 MDT as seen from 11.36 deg. N, 83.11 deg. W., magnitude 0.9764. From JMLC, the eclipse will be seen as a partial eclipse from 9:17:03 MDT until 12:02:31 with 64% of the Sun being blocked by the Moon at 10:36:32.
11/01 15h MDT - Jupiter appears closest to Earth (3.9824 au)
11/02 23h MDT - Jupiter at opposition
11/03 - MST returns
11/16 - 1h MST - Mercury at greatest elongation 22.6 deg. E.
11/27 - As seen from JMLC the Moon will block the light from Spica before the star rises, but the emergence of the star from behind the Moon at 04:27:24.7 should be visible.
12/08&09 - 16:14:25 MST - Earliest sunset at JMLC
12/21 02:21 MST - Winter Solstice - Shortest day of the year at JMLC: 8h 52m 45s.
12/24 20h MDT - Mercury at greatest elongation 22 deg. W.
12/25 evening - Hanukkah (Jewish)
Planets: Also see notes, below. Dates, in this section, mostly refer to the date on which the night begins, "midnight" means the middle of the night, not always 12:00 A.M. For events at "midnight" the date refers to the start of the night in question. Dates associated with dawn or morning only are not referenced to the previous night. The data given here are valid for observers in western South Dakota.
Pairings, within 5 degrees:01/18 the Moon and Jupiter 3.7 degrees at dusk, 01/19 to 01/29 Mercury and Mars at dawn 0.25 degrees on 01/27, 02/10 the Moon and Saturn 2,6 deg at dusk, at dawn 02/12 to 04/04 Venus and Mars (0.6 deg on 02/22), 03/13 the Moon and Jupiter 3.2 deg, 04/03 to 04/17 Mars and Saturn (0.5 deg on 04/10), 04/10 the Moon and Jupiter 4.8 deg ay dusk, 05/31 the Moon and Saturn 1.85 deg at dawn, 06/26 the Moon and Saturn 4.6 deg at midnight and 2.8 deg at following dawn, 07/01 the Moon and Mars 3.9 deg at dawn, 07/07 the Moon and Mercury 3.4 deg at dusk, 07/30 the Moon and Mars 4.7 deg at dawn, 08/05 to 08/20 Mars and Jupiter at dawn (0.3 deg on 08/14) also at midnight on the nights 08/20 through 08/23, 09/01 the Moon and Mercury 4.3 deg at dawn, 09/16 the Moon and Saturn 2.6 deg at midnight, 09/24 the Moon and Mars 3.9 deg at midnight and 4.6 deg the following dawn, 10/05 the Moon and Venus 4.6 deg at dusk, 10/14 the Moon and Saturn 4.3 deg at dusk, 11/04 the Moon and Venus 3.9 deg at dusk, 11/10 the Moon and Saturn 1.2 deg at dusk and 2.1 deg at midnight, 12/04 the Moon and Venus 3 deg at dusk, 12/17 the Moon and Mars 1 deg ar midnight and 2.1 deg the following dawn.
Mercury: Mercury can only be seen when it is sufficiently high in the sky before sunrise or after sunset. Its appearances typically last only a few days at a time. On 12/27/2023 a morning apparition will start and extend to 01/29/2024 reaching an altitude of 9.6 deg on 01/07 and reaching a maximum brightness of magnitude -0.3 from 01/09 to 01/18. An evening apparition will begin on 03/09 with Mercury bright at magnitude -1.4 fading to -0.2 on 03/24 when the planet will be 12 deg above the horizon at dusk, after 04/05 Mercury will be below 3 deg at dusk. On 06/25 Mercury will again appear as an evening object and bright at magnitude -0.9 but fading as it reaches 6.6 deg above the horizon on 07/10 and magnitude -0.1 after which it moves closer to the Sun and exits from view after 07/27. As a morning object Mercury reappears as a dim object 08/26 (mag 2.4) but brightens up until it ends this apparition after 09/19 (mag -1.9); it will be highest above the horizon on September 5 and 6 (10.5 deg). On 11/12 it will begin an evening apparition at magnitude -0.3, but again fade thereafter to mag 0.3 at the end on 11/25; the high point will be on 11/19-21 at 3.8 deg (pretty low) and mag -0.2. The last apparition of the year will be in the mornings from 12/10 (mag 2.3) but brightening up to -0.4 on 12/22 when Mercury will be 10.7 deg above the horizon and mag -0.4 at dawn finishing the year at an altitude of 8.4 deg and continuing its apparition into 2025.
Venusstarts the year as a morning object low on the horizon, sinking lower day by day until it is lost in the Sun's light around 03/03,. It becomes a bright evening object around 08/15, and thereafter appears higher and higher after sunset while growing in brightness to magnitude -4.5 by the end of the year.
Marsappears as a morning object around 01/15 at magnitude 1.4 as it rises shortly before dawn. By 08/20 it rises before midnight and has brightened to mag 0.8 brightening to -1.2 by the end of the year when it still rises after dusk, but is visible most of the night.
Jupiterstarts the year as a bright magnitude -2.6 object which sets before dawn, but slowly dims as it sets earlier and earlier. By February it is too low to be seen around midnight and is mag -2.4. By early May it disappears into the Sun's glare, but reappears in mid-June as a mag -2.0 object at dawn. It rises before midnight by 08/17 (mag -2.2) and is an all-night object on 12/07 (mag -2.7) and finishes the year as an evening object setting before dawn.
Saturnstarts the year as an evening object (magnitude 0.9) until mid-February. It then reappears as a morning object around 03/31. By the night of 09/08 it is an all-night object at magnitude 0.6, and thereafter becomes an evening object for the rest of the year.
Full Moon Nights:01/24, 02/23, 03/24, 04/23, 05/22, 06/21, 07/20, 08/18, 09/17, 10/16, 11/15, 12/14. (See notes below.)
Observing The Sun -- WARNING -- WARNING -- WARNING !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Extreme caution must be used by anyone trying to view the sun. You must block most of the visible light, and virtually all of the UV and infra-red coming from the sun. Viewing the sun is inherently dangerous. Dark photographic materials are NOT designed to reduce sunlight to a safe level, especially UV and IR! If a filter slips off your telescope, or your binoculars, your eye can be permanently damaged before you can react. Sunlight concentrated by a lens or telescope can overheat a filter causing it to melt or crack, and then you or your equipment will be at severe risk; therefore, sunlight must be filtered BEFORE entering any optical instrument or camera. Prolonged viewing of the sun requires great care and knowledge. Viewing the sun safely requires previous study and setting up the equipment well in advance. Last minute preparation is likely to lead to disaster! Please be sure you know what you are doing, and that you have the proper equipment with secure attachments if you wish to view or record solar phenomena. Do not hesitate to seek help from an experienced observer.
About the precision and accuracy of the listed times for specific events: Where times are listed to a precision of one second, or better, it should be understood that the calculation process has yielded a result to that precision, but several caveats apply: (1) even though the calculation in question might depend only on TT, the quantities DUTC = TT-UTC, and DUT1 = TT-UT1, for future dates can only be estimated. For events that directly depend on DUT1, even TT becomes an estimate. (2) For most events, observational precision is difficult and expensive - if not impossible. The chief exception to this is a lunar occultation of a bright star; but even in this case there are difficulties requiring great care in recording the event, determining accurately the observer's position, and establishing the time with high accuracy (in general, battery operated clocks are rated as good only to one-second accuracy at best) and clocks that use GPS, or frequent NTP updates, are required for errors no more than one tenth of a second.
About the dates of religious observances: These dates are conceptually tied to astronomical phenomena, and cannot be simply predicted. In the case of Christian and Jewish festivals the dates are determined by rigorous, but complicated, mathematics. In the case of Islamic observances, many adherents believe that the calendar can only be determined from direct observation in each community; the dates shown here are determined algorithmically and should differ from direct observation by no more than a day or two. The numbering of years in the Roman system (A.U.C.), although relatively simple, is also shown because of its historical importance. For a table showing the dates of Ash Wednesday, Easter, and Eastern Orthodox Easter for 1900-2100 click here. For the dates of the Chinese New Year, see the note below.
About visibility of the planets: The narrative provided above on this page is specific to the latitude of the Journey Museum and Learning Center in Rapid City, South Dakota, (JMLC) and should be reasonably accurate for latitudes between 42 and 46 degrees north, but increasingly inaccurate for observers farther north or south. The dates given are for the date on which a given night begins. The times given are for the end of evening twilight (E), the middle of the night (m), and the start of civil twilight in the morning (M); they are specific to the vicinity of the observatory. The elevation of a planet above the horizon is given in degrees for those times - if the planet's elevation is at least 3 degrees. Click here for more detailed information.
About Full Moon Nights: On the night of a full moon, and for a few nights before and after, the brightness of the moon may hinder observation of objects other than the moon. It occasionally happens that two nights in succession "enjoy" being about equal in moon brightness. Click here for more detailed information on visibility of the moon (corrected 10/14/2016).
About "Super Moons": The Moon is "full" when it is 180 degrees away from the Sun (in right ascension) and thus appears fully illuminated. However, its distance (from the Earth's center to the Moon's center) varies as the Moon moves in its orbit, and ranges from less than 357,000 km (at perigee) to more than 406,000 km (at apogee). Naturally, it appears bigger when it is closer, and the popular press has taken to calling a full moon near a perigee that is particularly close to the Earth a "Super Moon". In this discussion, particularly close will be defined as closer than 357,000 km. The full moon of September 27, 2015 in the evening at a distance of 356,878 km thus qualifies as a Super Moon, and the next one was on the morning of November 14, 2016 at 356,520 km - this will be the closest Super Moon until 2034, but there will be less notable Super Moons in 2018, 2019, 2025, 2026, 2028, 2029, 2032, and 2033 also.
About Lunar Occultations: The moon can, for a time, block an observer's view of a star or a planet. Only occultations of bright stars and bright planets are listed on this page; and only if the event is visible for an observer at the JMLC - the Journey Museum and Learning Center. The timing of an occultation is highly dependent on the observer's location, and is very sensitive to any inaccuracies in the computation of the coordinates of the moon and the star or planet involved. Therefore, accurate times for actual observations are of great interest. An extensive listing of lunar occultations is available here.
About Chinese New Year (Lunar New Year): This is determined by the date and time in China (UTC+8 hours) and is assigned to the date when a new moon first occurs on or after January 21. The last possible date for this is February 20. Once this date is calculated according to Chinese time, the same date is used also in the United States and the rest of the world (although, as an example, 6 PM in the evening on January 21 in San Francisco corresponds to 10 AM on the 22nd in China; moreover, it seems that celebrations outside of China may indeed start according to the time in China rather than local date-time). No correction for the equation of time is made when computing the date of the new year, i.e. the calculations are referenced to UTC+8 hours, not local solar time on a selected meridian. The actual time of day for the new moon is irrelevant unless it is so close to midnight as to introduce an ambiguity as to the date. For a listing of the dates from 2015 through 2050, click here.
About daily polynomials for lunar coordinates: The Astronomical Almanac lists the apparent right ascension, apparent declination, and true distance (light time not factored in) of the moon at zero hours Terrestrial Time for each day of the year.
The online web site at http://asa.hmnao.com/SecD/LunarPoly.html gives daily polynomials (for the years 2001-2021) for apparent right ascension, apparent declination, and horizontal parallax for any desired time during the day listed. Note: the coefficients listed by USNO are slightly different from those I list because I adjust the coefficients to minimize the discontinuities in the coordinates for 24 hours of one day versus zero hours of the next day.
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