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MOON LIKE A BRIDGE

To many it will be happened to observe, expecially in the southern regions, the particular phenomena in which the Moon,a little before the sunset, after the new Moon, has a characteristic shape of a small boat, with the cuspids turned towards the high one nearly to equal height. Much less observed the mutual phenomenon in which the our satellite before its rising appears with the cuspids towards the bottom that touching the horizon form an onlooker little bridge. If the illuminated part is under that dark one it speaks therefore about "Moon like a boat", while if the illuminated part is over it speaks about "Moon like a bridge". After the rising the height of the Moon increases, the scythe is straightened until to being perfectly vertical when the Moon passes in meridian. A lot interesting to photograp is obviously the moon "seated", when floating in the air seems to slip on our horizon. In March and still better in April, we will be able to begin to observe it; the Moon in the first days after the conjunction with the Sun will be lowland on the horizon with the characteristic position like a small boat. Since the phenomena is strongly dependent as from the latitude of the observer as from the ecliptical longitude of the Moon, will be well to begin in this spring to take to learn to see this event, initially unsatisfactory then more and more obvious inasmuch as the lunar ascending node will be to 270° in February 2011. Obviously all it has a precise astronomical explanation that are taken advantage of the trigonometry laws and celestial mechanics that regulate the complicated lunar motion. The variable that determines if and when we can observe the small boat is the parameter ZABL, zenithal angle of bright limb, that is the angle of position of the means point of the illuminated lunar border, calculated not regarding the lunar north but regarding the zenith of the observer. Since the illuminated face of the Moon is always revolted towards the Sun, this angle allows us therefore to know the position of the scythe regarding the horizon, expecially when the Sun is set down. If such angle is close to 180° the lunar scythe it assumes the shape to a little boat. Obviously it is not necessary that the precise value is caught up, we say that in range of approximately ±5° is however an optimal vision of the phenomenon. Necessary condition is that the phase is smaller of 50%, in how much the more is small and more the cuspids are sharp, and that the Sun is sufficiently distant to allow to see the Moon to the twilight.

The ZABL depends a lot from the latitude of the observer: it appears obvious that in the equatorial regions, in which the ecliptic it is much tilting on the horizon, it is frequent to see the Moon as a boat, while in Italy it is rarer, and at the latitudes beyond the 50° it is quite impossible. Therefore it can even succeed that two places distant they also only a pair of latitude degrees are one excluded and one favorable to the observation. In the following table are indicated the cities from which the phenomenon will be visible, with the times of beginning and ending observation, based on the parameters over indicated to you. In any case it will be well to watch carefully towards the west after the sunset of the Sun in order to notice the first possible the lunar scythe and to prepare the photographic equipment.


ANCONA

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.

AOSTA

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.

BARI

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.

BOLOGNA

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.

CAGLIARI

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.

21/ 7/2012   6:50  350.2    5    2    28
21/ 7/2012   7: 0  350.5    5    4    30
21/ 7/2012   7:10  350.7    5    6    32
21/ 7/2012   7:20  350.8    5    8    34
21/ 7/2012   7:30  350.9    5   10    35
21/ 7/2012   7:40  351.0    5   12    37
21/ 7/2012   7:50  350.9    5   14    39
21/ 7/2012   8: 0  350.9    5   15    41
21/ 7/2012   8:10  350.8    5   17    43
21/ 7/2012   8:20  350.6    5   19    45
21/ 7/2012   8:30  350.4    5   21    47
21/ 7/2012   8:40  350.1    5   23    49

20/ 8/2012   7:40  350.4    9   -0    33
20/ 8/2012   7:50  350.2    9    1    35

CAMPOBASSO

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.

CATANZARO

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.

21/ 7/2012   6:10  350.3    5    1    26
21/ 7/2012   6:20  350.6    5    3    28
21/ 7/2012   6:30  350.8    5    4    30
21/ 7/2012   6:40  351.0    5    6    32
21/ 7/2012   6:50  351.2    5    8    33
21/ 7/2012   7: 0  351.3    5   10    35
21/ 7/2012   7:10  351.3    5   12    37
21/ 7/2012   7:20  351.3    5   14    39
21/ 7/2012   7:30  351.3    5   16    41
21/ 7/2012   7:40  351.2    5   17    43
21/ 7/2012   7:50  351.0    5   19    45
21/ 7/2012   8: 0  350.8    5   21    47
21/ 7/2012   8:10  350.5    5   23    49
21/ 7/2012   8:20  350.1    5   25    51

20/ 8/2012   7:10  350.8    9    0    33
20/ 8/2012   7:20  350.6    9    2    35
20/ 8/2012   7:30  350.3    9    3    37

FIRENZE

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.

GENOVA

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.

L AQUILA

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.

MILANO

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.

NAPOLI

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.

PALERMO

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.

21/ 7/2012   6:20  350.9    5    0    25
21/ 7/2012   6:30  351.2    5    2    27
21/ 7/2012   6:40  351.5    5    4    29
21/ 7/2012   6:50  351.7    5    6    31
21/ 7/2012   7: 0  351.9    5    7    33
21/ 7/2012   7:10  352.0    5    9    35
21/ 7/2012   7:20  352.1    5   11    37
21/ 7/2012   7:30  352.1    5   13    39
21/ 7/2012   7:40  352.1    5   15    41
21/ 7/2012   7:50  352.0    5   17    43
21/ 7/2012   8: 0  351.8    5   19    45
21/ 7/2012   8:10  351.6    5   21    47
21/ 7/2012   8:20  351.4    5   23    49
21/ 7/2012   8:30  351.1    5   24    50
21/ 7/2012   8:40  350.7    5   26    52
21/ 7/2012   8:50  350.2    5   28    54

22/ 7/2012   7:40  350.0   11    3    41
22/ 7/2012   7:50  350.1   11    5    43
22/ 7/2012   8: 0  350.1   11    7    45
22/ 7/2012   8:10  350.0   11    9    47

20/ 8/2012   7:20  351.6    9   -0    33
20/ 8/2012   7:30  351.4    9    1    35
20/ 8/2012   7:40  351.1    9    3    37
20/ 8/2012   7:50  350.7    9    5    39
20/ 8/2012   8: 0  350.4    9    7    40

PERUGIA

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.


POTENZA

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.

ROMA

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.

TORINO

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.

TRENTO

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.

TRIESTE

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.

VENEZIA

DD MM YYYY  HH MM   ZABL    K  ALT  ALT.S.


K = % of illuminated Moon
ALT. = height of the Moon above the horizon, in degrees
ALT.S. = height of the Sun above the horizon, in degrees

ALL TIMES ARE IN T.D.T.

See also Standing Moon
See also Moon like a boat