MOON-JUPITER-VENUS-CONVENTIONS ============================ John Pazmino NYSkies Astronomy Inc www.nyskies.org firstname.lastname@example.org 2008 December 21
Introduction ---------- On 1 December 2008 there was a tight convention of Moon, Jupiter, and Venus in the southwest at dusk. For NYSkies territory the sky was on-off cloudy during the day with low chance of seeing the apparition. Clouds broke after sunset to reveal the triplet dancing over the skyline. This show was mentioned in news media for about a week before, with the suggestion to watch Jupiter and Venus approach on their way to conjunction. The Moon, rounding new phase, would join them on December 1st to form the convention. Clouds rolled in again after dark to close the show. Altho it cleared up later at night, the planets by then set. Never the less, a substantial segment of the public and most home astronomers got good views during the clear period. A few news accounts mentioned that this convention (as a meet up of three or more planets is sometimes called) will next occur in year 2050. I could find no reason for this claim, in as much as I personally recall several Moon-Jupiter-Venus conventions in the last 20 and more years. I did my own inquiry about these apparitions.
The planets --------- Here I include, like the ancients, the Moon and Sun as 'planets'. Moon, Jupiter, and Venus are consistently the brightest planets in the night sky. The phase of Venus about compensates for her angular diameter to keep her roughly the same brilliance all around her orbit. She is alway brighter than other planets, except the Moon when more than a thinner crescent. Jupiter does vary slightly over his orbit but remains quite among the brightest of stars in the sky. However, like in 2008, Jupiter can look utterly anemic next to Venus, in spite of his luster at night. Mercury, Mars, and Saturn are usually dimmer than Jupiter and Venus. Mars can at close oppositions excede Jupiter, as he did in 2003, but normally he about equals Jupiter at best. Saturn's brightness is strongly modulated by the tilt of his rings. When open, they add to the presented area of the planet to reflect more sunlight to us. In 2009 the rings are closing up so the planet will be rather dimmer than usual, with sunlight coming to us only from his globe. In spite of the variation in planet brilliance, a planet is unmistakable in the sky for being the bright intruder into a given constellation. If you know your stars flanking the ecliptic, you'll always recognize a planet among them. in this article the planets are symboled by their initials. -------------------------------------------------- Sun $ (fancy 'S', avoid conflict with Saturn) Mercury H (Hermes, avoid conflict with Mars) Venus V Moon L (Luna, avoid conflict with Mars) Mars M Jupiter J Saturn S ----------
Outer planets ----------- The outer planets, Uranus, Neptune, Pluto, are also called telescopic or modern planets, ar skipped here. almanacs routinely note aspects of these with the other planets, but in most cases the alignment is a geometric one not readily observable. This is specially so when they conjunct with the Moon, whose luminance almost always overpowers them. many home astronomers configure their planetarium programs to leave out the three modern planets to maintain the bare-eye view of the sky. Uranus and Neptune are in empty parts of the sky and can be found with detailed starcharts. Pluto is entering the western edge of the Milky Way, where there are thousands of stars of competing brightness to hide among.
Conjunctions ---------- When two planets, or a planet and a bright star, attain to the same ecliptic longitude, they are in conjunction. Some astronomers calculate conjunctions by equality of right ascension. Both are valid but can yield different moments for the conjunction. It can also happen that there is a conjunction in longitude but not in right ascension or vice versa. The star must be within the zodiac, within 8 degrees of the ecliptic to be considered for conjunction. It is possible to compute a conjunction of Saturn with, say, Sirius, being that Sirius has an ecliptic longitude that at some time or other is touched by Saturn. No one in his right mind will list such an event! The star-planet meet has to be within a few degrees to be an attraction in the sky. When two planets are in conjunction, by equal longitude in this article, they may be far apart in ecliptic latitude. There is a subjective notion of two planets being associated when they are close enough in latitude. What is this margin of approach? There is no generally agreed on limits. However, if the latitude difference is too great, the planets may not be treated as associated, but are just two nice bright stars in the same quarter of the sky. Hence, conjunctions are usually calculated by the longitude (or right ascension) with the latitude (or declination) ignored. The result is a bunch of geometric conjunctions that are some how not really all that special.
Sun and Moon ---------- Conjunctions with the Sun are not observable well from the ground because the planet is masked by daylight. The reason to list such conjunction is to alert for the crossover of the planet from morning to evening, or vice versa, sky. The superior planets have only one conjunction, Conjunctions with the Sun are grouped by inferior and superior planet. The inferior planets are Mercury and Venus, called such because they are in the ancient scheme of the heavens below the Sun in the spheres of the world. Mars, Jupiter, and Saturn are the superior planets because their spheres sit above the Sun. Un the real solar system the classification still holds. Mercury and Venus run in lower orbits than that of Earth, as seen from the Sun, while the orbits of the other planets are higher than Earth's. A superior planet has only one conjunction with the Sun, a superior conjunction, when it crosses from evening to morning sky. An inferior planet has two, on when it passes closer to us than the Sun and when it passes behind the Sun. The former is inferior conjunction, the transition of the planet from evening to morning. The latter is superior conjunction, the planet passing from morning to evening. The seeming opposite sense of the crossing for a superior and inferior planet comes from the direction of motion relative to the Sun. An inferior planet in superior conjunction overtakes the Sun from the morning (west) side and moves to the evening (east) side. In its inferior conjunction the planet slides backward, in retrograde motion, to get around the Sun from evening to morning. A superior planet in its one conjunction lags the Sun, the Sun overtaking it. It slides toward the Sun from the evening (east) side to the morning (west). The Moon is a special planet orbiting Earth, not Sun. It overtakes the Sun in an inferior conjunction to get from morning to evening sky. She is 'new' at the conjunction. The figures here clarify the motions of planets near conjunction, with the Sun held fixed. North is up for a northern hemisphere bare eye view. Mind well that a planet east of the SUn remains in the sky after sunset, in the western sky, as an evening star. Vice versa for a morning star.
evening sky | morning sky | <----------H,V----------< inf planet, sup conj east $ west >----------H,V----------> inf planet, inf conj
evening sky | morning sky | >--------M, J, S--------> sup planet, sup conj east $ west
evening sky | morning sky | <-----------L-----------< Moon, inf conj east $ west
East is west, west is east ------------------------ One of the puzzling features of planet apparitions for the newcomer is the use of the directions east and west. Because the planets trend eastward thru the zodiac, the eastward motion is direct or prograde. When a planet reverses direction to travel westward for a while, it is in retrograde motion. This is against the sense of diurnal motion of the entire sky, where westward is direct motion. There is no retrograde concept here because, thankfully, Earth has a nearly uniform and continuous rotation in only one direction, that which imparts the westward drift of th stars across the sky. The distance downrange along the ecliptic, neglecting its latitude from the ecliptic, from the Sun is its elongation. Numericly it is the (longitude of planet) - (longitude of Sun). Positive elongations mean the planet is EAST of the Sun, farther downrange in prograde motion. A negative elongation puts the planet WEST, uprange, of the Sun. When a planet has western elongation, it lags the Sun in the diurnal rotation of the sky and remains in the sky after sunset. It is visible in twilight, usually in the western part of the sky as an evening star. See that an EASTERN elongation puts the planet generally in the WESTERN sky in dusk. Similar logic applies to the western elongations in the eastern sky at dawn. It is easy to mix up the sense of elongation and visibility! When a planet is near 180 degree elongation, whether east or west, we lose track of where the Sun is. The planet is seen in a night sky with no obvious location for the Sun far below the horizon. As long as the planet's elongation is positive, east, it is in the sky at sunset and will be seen in the early night hours. When the elongation becomes negative, by progressing farther along in the ecliptic to start catching up to the SUn from the west, it is no longer in the early night sky. It rises after sunset and is best viewed in the owl or predawn hours. A corollary to elongation are the stations. When a planet enters its retrograde loop it stop advancing in longitude and begin to backtrack. The turning point is the station and is either east or west of the Sun. The confusion comes in when you look at a typical diagram of a retrograde loop. The planet moves in prograde, stops, reverses, swings backward in retrograde motion, stops again, and resumes prograde motion. One station is east of the middle of the loop; the other, west. The east station is really the WESTERN station and the west station is really the EASTERN station! The problem is that all the while when the planet is doing its loopy-loop, the SUn continues his own prograde march thru the zodiac. When the planet stops to enter the loop it is CLOSER to the Sun in the western direction being than less than 180 degrees west elongation. When it stops again to leave the loop it is closer to the SUn in the eastward direction, with an east elongation less than 180 degrees. If your planetarium program can show the entire sky at once, or some very large portion of it, try animating a retrograde loop and see how the planet's elongation from the Sun switches from western to eastern during the loop.
SOHO pictures ----------- Until the late 1990s it was impossible, save in extremely special situations, to observe a planet near solar conjunction. The daytime sky totally veiled out the planet. There was also the hazard of accidently looking into the Sun, specially with optical instruments, when hunting for the planets. Severe and permanent eye damage could result. In the 1990s the SOHO satellite, built to study the Sun, was placed at Earth's L1 libration point, about 1-1/2 million kilometers toward the Sun. At this point the satellite with adjustment by onboard rocket stays in line with the Sun so it rise and sets with him. Comms with SOHO are by radio on frequencies where the Sun is relatively quiet. Among the instruments on SOHO are two cameras that photograph the Sun continuously in a wide and narrow field. The wide field camera is LASCO, covering a circle 7 degrees radius centered on the Sun. The Sun himself is masked by a paddle extending into the field; this shows in the pictures. Intended to record the outer corona, the camera also records stars beyond the Sun! By examining pictures on sequential days, the motion of the Sun thru the zodiac can be followed. The pictures soon turned up many comets, otherwise invisible from Earth. These, the SOHO comets, now number some 2.300 and account for MORE THAN HALF of ALL comets recorded in human history! That is, you right now live in a time when you could 'see' more comets, thru the SOHO pictures' than all the astronomers of all the ages before you. Besides the comets, planets in conjunction pass thru the camera field. You can select from the SOHO archive those pictures near a given conjunction and see the planet among the stars. A series of pictures traces the planet's motion relative to the Sun and stars in accordance with the diagrams above.
Superior planets -------------- The superior planets trend eastward thru the zodiac passing from a one sign or constellation into the next. Near opposition, when they are near 180 degrees from the SUn, they execute a looping motion and regress backward in the stars for a few weeks or months. This is the retrograde loop. It is merely an effect of our line of sight to the planet from a moving earth temporarily overtaking it on an inner orbit. This happens in the sky opposite the Sun, so the planet rises near sunset and sets near sunrise. It crosses the local meridian near midnight. A superior planet can not conjunct with Venus when near its opposition or in its retrograde loop. it may pass Venus only while it its prograde, eastward, direct motion.
Inferior planets -------------- Mercury and Venus, because their orbits are enclosed by Earth's, are constrained in angular distance they can recede from the Sun. Mercury can excurse from the Sun a maximum of about 27 degrees east or west. He must then retreat back to the Sun. The moment of greatest elongation is, erm, greatest elongation. Venus can range to about 47 degrees from the Sun and, like Mercury, has greatest elongations on both east and west sides of the Sun. Conjunctions of other planets with Venus must take place within this range 47 degrees east or west of the Sun, so they are visible only in dawn or duck along with the very Venus herself. Conjunctions of other planets with Mercury are hard to observe because Mercury is usually smothered in twilight. Such events are useful to FIND Mercury when otherwise you have trouble spotting him. He is then next to the other brighter planet. Both Moon and Venus are favorite markers for finding Mercury.
Computation --------- It is trivial to compute when conjunctions occur between two planets. Many astronomy computer programs do this by specifying the two planets and a date range. Others include two=planet conjunctions in their canned calendar of celestial events, so all you need give is the date range. Conjunctions of three planets, a convention as it's sometimes called, is trickier. You have to hunt for conjunctions of one pair of planets AND ALSO those of the second pair. You can do this by brute force, computing the two separate sets of conjunctions and manually picking out those which occur on the same date. This may the be simplest way for a short look into the future, like a year or two, Conjunctions among pairs of planet are tabulated in celestial almanacs and calendars but not always for all of them. The author picks out the 'nice' ones by some subjective choice. Conventions of three planets are noted by the three separate pair conjunctions. Here's an example from the event of 2008 December 1:
--------------------------------------- 2008 Nov 30 19h - Venus 2d S of Jupiter Dec 1 10h - Jupiter 1.3d N of Moon 11h - Venus 0.8d S of Moon -----------------------------
You could suppose that Jupiter and Venus are still close together when the Moon comes by a few hours after their own conjunction. The date is in EST for New York. An other way is to set a planetarium program in slow animation and watch the screen for planet alignments. You have to stay awake and ride the 'pause' function to stop the motion and write down the date and time. You may have to do a single-step back and forth to get the best alignment. This method can be fun, fiddly, fatiguing. You could by a lapse of attention miss events.
Astrology?! --------- Astronomers narrowed down their concern with alignments of the planets, being that these have nothing to do with earthly fates and fortunes. The main residual configuration of planets still listed in almanacs are those relative to the Sun. These include conjunctions and oppositions, and greatest elongations. These are handy to assess the visibility of the planets in the sky. Elongations in general are almost only calculated relative to the Sun. To get the elongation of one planet relative to an other, yu must manually subtract the solar elongations. You have to mind the sense of the subtraction. Astrologers, on the other hand, maintain a set of alignments, which they call 'aspects', relative to each planet, not only to the Sun. To them, the proximity of planets combines their power to influence your life. Thus they care about the opposition of one planet with an other, when they stand 180 degrees apart in longitude Over the years, seeking 'better' fortune=telling success, astrologers now use the same computation tools as the astronomer. These tools allow computation of all kinds of alignment among planets and stars, most of which were long ago abandoned by astronomers. Thus, in an ASTROLOGY computer program, it is likely that three- way conjunctions can be found in a direct way. Such a program was used to develop the table below. A planetarium program was then used to simulate each event. Do note that the fancier, many free for the download!, astrology programs have quite the same precision and accuracy of mainstream astronomy programs for computing the locations and motions of the planets and stars. They sometimes include, as an extra 'goodie' for the astrologer, legitimate astronomy information about the planet, like phase, distance, angular size. So, if you can walk straight thru the astrology house and leave out the back door, it is very handy to have an good computation astrology program at the ready.
Conventions --------- It is essentially impossible to have equality of longitude among three planets at once. Each pair achieves equality with the third out of line. The best to look for is a close grouping, the convention, of the three such that an observer considers them obviously associated together and not just three separate stars in the sky. Some leeway or tolerance is needed when looking for conventions. Not exact equality but some approach within so many degrees. In this way, all three can be close enough without demanding they be exacta mente on the same longitude of the ecliptic. What's needed is a zone around each planet within which an other can enter to form a conjunction. Astronomers have no such concept. Astrologers, for their own reasons, assign such zones by which the planet forces mix together when they come too close. This zone is the 'orb'. When the orbs of two planets touch or overlap, the planets are in conjunction and are extra active against you, even if they don't have the same longitude. The problem is that there seems to be no accepted radius for these orbs. Over the ages astrologers assigned various radii in degrees for the planets, sometimes changing them according to their brightness or elongation from the Sun. Astrology programs have a panel to set the orbs if the default values don't suit you. For my explorations, I left the orbs alone. Astronomers do have a residual concept of orb in the twilight zone around the Sun. If stars or planets are within 15 (this varies among astronomers) degrees of the Sun, they are too hard to observe. This accounts for the 'blackout' period around solar conjunction, when the planet is nowhere in either morning or evening sky. You must wait until the planet gets far enough away from the Sun. beyond 15 degrees, to observe it again. For here, a three-way conjunction occurs when the orbs of the three planets touch or overlap all together. Having the date of this event in hand, I simulated the event with a planetarium program. The value of the orbs embedded in the astrology program didn't matter because I manually inspected the event on screen. The output from the astrology program is a range of dates for each event. The orbs take time to move across each other. It's one day if the Moon is one of the planets on account of her swift motion, some 12 to 13 degrees per day downrange along the zodiac. For the far slower moving planets, a degree or so at most per fay, the range of orb contingency is a few days.
Moon-Jupiter-Venus ---------------- With Venus as one of the convening planets, the event must take place within 47 degrees of the Sun. This restricts visible hours to those in dusk or dawn, according as Venus be an evening or morning star. The convention is seen in the western sky in dusk or eastern sky in dawn. In the dawn, the planets rise before the Sun, perhaps in dark sky, and are all up as twilight waxes. Evening events have the planets in the sky in twilight, after which they set, sometimes in a dark sky. The Moon is always within a couple days age from new phase, so she is always a crescent for this convention. You can not get a Venus conjunction with the Moon for 1st quarter thru full thru 3rd quarter. Jupiter is near his superior conjunction. No Venus conjunctions can occur near his opposition or retrograde loop. To generate the table below I asked the astrology program for dates when Venus conjuncts the Moon AND ALSO Jupiter conjuncts the Moon. I allowed the program to apply the default orbs for checking contingency. In a few cases, the Moon could stay near Venus and Jupiter for two days, being near a one on the first day and near the other on the second. I wither chose the 'nicer' of the two or kept both for being pretty good.
Latitude ------ The fact that a conjunction occurs does not mean the apparition is visible in the sky. In particular, many astronomers check only the elongation of the Moon or other planet from the Sun to declare a visible event. As long as the conjunction is farther than 15 (or what ever) degrees from the Sun, they announce the event. Elongation alone is not enough to determine visibility! In an assessment parallel to that for first-Moon visibility in some cultures, there are many other factors to consider. It is simplest to roll these together thru a planetarium simulation than to figure an analytical method. First is the latitude of the planets from the ecliptic. Since we're dealing with three planets, I used the Moon as the representative of the trio. She can deviate from the ecliptic by up to 5-1/2 degrees north or south. This deviation is what makes new Moons usually miss crossing the Sun to cause a solar eclipse. She passes too far north or south of the Sun. For an evening apparition in New York a southern Moon places her closer to the horizon than the ecliptic and lowers the visibility of the convention. A northern Moon raises the apparition into higher sky, above the ecliptic, for better visibility. The figure here clarifies this factor.
\ \ V J \ L---northern Moon \ V J \ southern Moon---L \--ecliptic \ \ ================$======--horizon
Inclination --------- The slope of the ecliptic near the horizon, staying with a New York evening event, varies with the season. It is more vertical in winter and spring and less so in summer and fall. In 2008 this caused Venus, while far from the Sun by elongation, to be missed behind skyline and haze for several months after she entered the evening sky. it wasn't until the coming of fall when the ecliptic started too tilt up that she came over the skyline. For a Moon on the ecliptic, the effect is illustrated here
\ \ L---steep ecliptic \ V J \ \ \ \ shallow ecliptic--L \ V J \ \ \\ ==============================$=====horizon
Elongation -------- I measured the actual angular separation of the Moon from the Sun for each event, rather than just the elongation. The elongation is only the difference of longitude while separation is the great circle arc between the two bodies. It is the hypotenuse of the triangle of Sun. Moon, and ecliptic point of lunar longitude. In the planetarium program it was far easier to bank off of the Moon herself with its distance tool.. If the Moon is too close to Sun, she rises too late before him or sets too soon after him. She is seen in strong twilight, which may veil the other planets from easy view. Note well that the maximum distance of the Moon from Sun is NOT the greatest elongation of Venus, 47 degrees. The configuration of the trio can be such that the Moon is the farthest east (for evening event) of the three, with Venus either the middle or western planet. Thus in the table, there are some distances of Moon rather more than 47 degrees. Lo here the figure
\ V J L--large distance from Sun \ ecliptic--\ \ V J L--small distance from Sun ================================horizon $
How close is close? For this study I let the Sun stand 12 degrees below the horizon, the begin or end of nautical twilight. I then took the altitude of the Moon. If this was less than 5 degrees, I deemed the event too hard to see in twilight. Of course, there were many instances when the Moon was so close, her altitude was negative; she was below the horizon. These invisible events I call 'day' events because they possibly with care and skill be observed while the Sun is up. The optimal time for this attempt when the Moon is near her culmination. Between Sun rise/set and nautical twilight you could watch the event in a bright twilight. It's just harder to see and appreciate and would not be a good one for public attention.
Configuration ----------- I did not try to draw ASCII diagrams of the events. I do in the table give the order along the zodiac of the planets, including others that happen to be near the trio. I list them from west to east. You lose the exact shape of the triangle, whether full, flat, or thin. In the latter case, two of the three planets are close with the third a distance away. For an evening event, planets east of the Moon tend to be in higher altitude; western, lower. In the morning, the western planets tend to be higher than the Moon; eastern, lower. At least you get some idea of where the planets are relative to the Moon by the sequence of the letters. If a bright star is among the planets, I note iy in the comments.
Constellation ----------- I list the constellation where the Moon is. based on the formal frontiers. This is not the zodiac sign. The other planets may be in adjacent constellations. Recall that the zodiac sweeps across many constellations other than the traditional 12. Remember that the frontiers are precessed with the stars. This is a fact sometimes missed in planetarium programs when set to remote dates! Stars on a frontier could migrate by proper motion into the adjacent constellation.
Table of events ------------- This table gives Moon-Jupiter-Venus conventions from 1990 thru 2050 for New York City. The date can be a day off from that cited in calendars and almanacs for other timezones or UT. 'Sun' is the distance of the Moon from the Sun at either dawn of dusk, which ever is the better situation 'Vsbl' is the visibility of the event, fin dawn, dusk, or only by day. The last is assigned if at dawn or dusk the Moon is less than 5 degree altitude or one of the planets is below the horizon. 'cns' is the constellation where the Moon is. 'W->E' is the the west-to-east sequence of the planets.
----------------------------------------------- EST date Sun vsbl alt cns sep W->E comments ----------- --- ---- --- --- --- ----- ------- 18-Aug-1990 27W dawn +11 Cnc 3.4 LJV Beehive 15-Jun-1991 45E dusk +14 Cnc 4.5 JVML Beehive 10-Aug-1991 9E day -11 Leo 9.5 $JLHV Regulus 6-Sep-1991 27W dawn +12 Cnc 13 LVHJ Regulus 4-Oct-1991 42W dawn +28 Leo 6.2 LVJ Regulus 12-Nov-1993 19W day + 4 Vit 4.5 JVLH Spica 7-Oct-1994 39E dusk + 6 Lib 8.1 JVL Venus down 3-Nov-1994 5W day -10 Lib 9.1 VL$J 27-Jan-1995 46W dawn +17 Oph 7.4 JVL 23-Nov-1995 18E day + 2 Oph 5.7 LJMV 6-Feb-1997 16W day + 0 Cap 3.2 JLV Venus & Jupiter down 23-Apr-1998 43W day + 4 Aqr 3.6 JVL 3-May-2000 12W day -13 Cet 11 VHL$JS 27-Aug-2003 6W day - 7 Leo 4.4 JL$V Regulus, dawn do 5E day - 7 Leo 6.1 J$LV Regulus, dusk 9-Nov-2004 40W dawn +25 Vir 4.6 LJVM Spica 6-Sep-2005 34E day + 3 Vir 3.8 LJV Spica 20-Nov-2006 7W day -10 Lib 8.2 ML$JV 4-Feb-2008 32W day + 2 Sgr 3.9 JLV 1-Dec-2008 45E dusk +17 Sgr 2.7 JVL 14-Feb-2010 9E day - 3 Aqr 3.8 $LVJ 30-Apr-2011 32W day + 4 Psc 11 LVHMJ Venus & Jupiter down 17-Jun-2012 25W day + 1 Tau 5.6 JLV Aldebaran/Pleiades, Ven down 15-Jul-2012 43W dawn +18 Tau 4.8 JLV Aldebaran/Pleiades 9-Jun-2013 15E day - 6 Ori 8.8 JLVH 23-Aug-2014 24W dawn + 6 Cnc 6.7 LJV Beehive 19-Jun-2015 42E dusk + 8 Cnc 8.5 LVJ Beehive 20-Jun-2015 52E dusk +14 Leo 7.0 VJL 18-Jul-2015 34E day + 1 Leo 4.6 JLV Regulus 6-Nov-2015 57W dawn +40 Leo 8.2 LJMV 7-Nov-2015 46W dawn +30 Vir 7.7 JMLV 2-Sep-2016 18E day - 4 Vir 4.0 LHJV 16-Nov-2017 23W dawn + 9 Vir 6.6 LJV 17-Nov-2017 12W day + 0 Lib 5.1 JVL 28-Nov-2019 28E dusk + 6 Sgr 3.9 JVLS 10-Feb-2021 17W day - 7 Cap 5.0 SVLJH 26-Apr-2022 41E day + 0 Aqr 4.3 SMLVJ 22-Feb-2023 36E dusk +21 Cet 5.1 VLJ 20-Aug-2025 35W dawn +21 Gem 6.9 JLVS Castor/Pollux 31-Aug-2027 5E day -10 Leo 8.5 J$LVH Regulus 14-Nov-2028 28E dawn +11 Vir 4.0 JVL Spica 10-Sep-2029 36E day - 1 Vir 5.5 LJV Spica 25-Nov-2030 8E day - 7 Oph 3.6 $JLVH Antares 8-Feb-2032 39W dawn +12 Sgr 7.6 LJV 5-Dec-2032 39E dusk +18 Sgr 7.0 LVJ 19-Feb-2034 13E day + 1 Aqr 2.9 VLJ Venus down 25-May-2036 8W day -14 Tau 10 LJ$V Aldebaran/Pleiades, dawn do 7E day -14 Tau 7.6 J$LV Aldebaran/Pleiades, dusk 21-Jun-2036 38W dawn + 5 Tau 12 MVJH Aldebaran/Pleiades, Jup down 19-Jul-2036 55E dawn +24 Tau 10 LVJ Aldebaran/Pleiades 14-Jun-2037 17E day - 4 Gem 8.3 JLV Castor/Pollux 28-Aug-2038 26W dawn +12 Cnc 8.2 LJHV Beehive 25-Jun-2039 48E dusk +18 Leo 8.1 NLJS Regulus 8-Sep-2040 27E day + 2 Vir 5.5 JHSVLM Spica, Jup & Ven down 22-Nov-2041 15W day + 1 Lib 3.9 SLJV Venus down 5-Feb-2043 53W dawn +13 Oph 8.6 LJV 3-Dec-2043 25E day + 1 Sgr 5.5 HLJV 15-Feb-2045 17W day - 6 Cap 6.9 LVJ 2-May-2046 42W dawn + 9 Psc 5.8 LVJ 27-Feb-2047 35E duck +23 Psc 8.0 MVLJ 24-Aug-2049 44W dawn +26 Gem 8.8 LJV Castor/Pollux 22-Jun-2050 43E dusk + 7 Cnc 8.5 JVL Beehive ----------------------------------------------
Conclusion -------- It is evident from the table that elongation or distance of the Moon from the Sun is insufficient to make a conjunction visible. The slope of the ecliptic and the latitude of the planets must also be considered. This is easiest done by simulating the event with a computer planetarium and taking measurements off of the screen. Occasionally an event can be seen a day earlier in dawn or a day later in dusk when the Moon is in higher altitude. The triangle is looser but you do see the three bodies in alignment. In addition, the shape of the trigon is a factor in the aspect of the convention. A roughly equilateral triangle is overall more pleasing than a thin or flat one. Presence of other planets or bright stars also adds to the pleasure of the event. A major factor often neglected in announcements is the timezone or longitude of the observer. Dawn and dusk migrate around the clock with longitude, carrying the Moon with them. The convention may be good for one timezone but loose for an earlier or later one. The lesson here is that it takes intimate understanding of the workings of the planets and sky to properly call attention to the better events and pass over those of only geometric interest.