The paper discusses moon sighting and the use of modern technology. It starts by explaining how a new moon occurs, then goes on to explain the different technologies that aid moon sighting.
The methodology for determining the appearance of the crescent has since assumed different dimensions. Apart from the actual physical sighting by the naked eye, these days, the exercise can also be done effectively with the use of astronomical calculation, the use of new technological devices e.g telescope etc, and the use of planetarium software on computers to aid naked eye sighting which is recognized by Sharia in Islam.
The Moon orbits the Earth once every 29.53 days (average of synodic month). Because of this revolution, phases of the Moon changes as the Moon’s position changes relative to the Earth and the Sun.
So, during the Moon’s orbit, if the Moon, Earth and the Sun lie exactly at the same line and the Moon is in the middle, the Sun will illuminate half of the Moon that faces it, and the other half which faces us, will be dark because it does not reflect rays of the Sun
At this point, the Moon is called Astronomical new Moon. After that, the Moon continues orbiting the Earth and begins to reflect a small amount of Sun’s rays and now we see the Moon as a very small waxing crescent. Afterwards, it becomes first quarter, full Moon, last quarter, waning crescent and then wane again. The New Moon phase is certainly a unique instant all over the world. But in reality the Sun, the Moon, and the Earth are viewed as disks not points, and so, observers on the Earth in different locations will not see the centers of the Sun and the Moon at the same longitude in the same instant. The difference may reach up to four hours. This would be obvious during a solar eclipse, which can be considered as a “visible” New Moon phase, since it is well-known that a solar eclipse does not begin at the same instant all over the world.
For most purposes, it is suitable to consider the New Moon phase as a unique instant all over the world, and so nearly all the astronomical books and magazines publish times of New Moon phase as a unique instant, which is for the center of the Earth. But to observe the very thin crescent(Hilaal) shortly after the New Moon phase, and to know the exact interval between the New Moon phase and the observation time (Moon’s age), we should adopt the instant of the New Moon phase that occurs from the location of observation..
Moon’s age is measured from the moment of conjunction (New Moon). We often say this Full Moon is 14 days old, which means that the number of days after the new Moon is 14. And we say this crescent is about 2-3 days old.
Generally, through a telescope, it is not likely to see a crescent that is less than 12 hours, i.e. if we want to observe the thin waxing crescent to determine the beginning of an Islamic month, the Moon should be in the wane phase (New Moon) 12 hours ago or more and not less than 17 hours with the unaided Naked eye.
The new Moon is located exactly at the Sun’s direction, so the Sun’s glare will prevent us from seeing it, in addition, the percentage of the reflected rays out of the new Moon is nearly equal to zero, and this percentage increases as the Moon’s age increases. GENERALLY human eye through a telescope can’t detect any reflected rays on Moon if the Moon’s age is less than about 12 hours, while unaided naked eye cannot detect any reflected rays on the new Moon until after about 17 hours. The new waxing crescent is located near the Sun, so its not possible to sight it w until after Sunset, because it is obviously not possible to observe the thin waxing crescent before Sunset. In addition, we must wait a reasonable time until the twilight decreases, i.e. until we can differentiate between Moon’s light and twilight glare, a 10-minute period could be enough sometimes to detect the thin waxing crescent.
The Moon, like the Sun, rises from the East and sets after about 12 hours at the west (with exceptions at high-latitude areas) each day, and since the waxing crescent lies near the Sun, it will set after the Sunset. The new moon rises and sets at about the same time as the sun, but as the Moon moves in its orbit around the Earth, it will progressively move towards the Eas,t away from the Sun as the days passes by after the new Moon. The Moon will rise about 48minutes late after a day, that is why a new Crescent on a second day is seen for a longer period after sunset before it sets.
There are several factors that must be met in order to view the thin waxing crescent: Some of these factors are:-
· The crescent’s altitude.
· The angular distance between the centers of Sun and Moon.
· The Moon’s Lag time (the interval between the Sunset and the Moon set).
· The azimuth difference between the Sun and the Moon.
Astronomical Calculations of the Crescent
Moon Astronomical calculations is done by knowing the following factors:
1. The time of a new Moon conjunction (New Moon) must be determined, and this time is accurately calculated. For sure there is no chance for any error. Based on the time of the conjunction of the new moon occurred, it is possible to calculate the time that the moon will be visible with an optical aid or the naked eyes.
2. Some other factors are, the angular distance between the centers of the Sun and the Moon at Sunset, Sunset time and the Moon set time, Moon’s staying period after Sunset, …etc.
Note: It is absolutely impossible to see the thin waxing crescent after sunset before conjunction (New Moon). Claims of sighting the thin waxing crescent before the New Moon instant, is like claiming of sighting the Sun before dawn, or seeing a baby before delivery”, ancients say.
Planetarium Software on Computers
Planetarium software is an application that renders a three dimensional image of the sky on to a two dimensional computer screen. Planetarium software allows a user to simulate daytime and night time on a computer, it. Such applications can be used to monitor the movements of celestial bodies. While some planetarium softwares are meant to be used exclusively on personal computers, some applications can be used to interface with and control telescope.
With planetarium software it is possible to determine the following.
1) Time of conjunction of a new moon.
2) Moon rise and moon set
3) Sun rise and sun set.
4) Angular distance between the center of the moon and sun.
5) Azimuth of the moon and sun.
6) Moon’s position at any given time.
7) Coordinates of the Moon.
8) Moon’s altitude.
OPTICAL AID (TELESCOPES AND BINOCULARS)
Telescope and binoculars help in sighting new crescents. It’s very important to know the coordinates of the moon in other to locate the moon easily.
From our point of view on the earth, the sky is sphere. If you stretch out or project the
Geographical coordinates of Earth into space, a grid work of celestial coordinates is formed on the Sky. And just like the earth spherical surface, the celestial sphere will have an equator, Poles and the equivalents of latitude and longitude. This makes it easy to measure positions on the Sky.
The celestial equator is a full 360-degree circle splitting the celestial sphere into the Northern and Southern celestial hemispheres or simply the Northern and Southern sky. It is the projection of our equator in space. It is directly overhead at the earth’s equator. Measurements North and
South on the sky are called declinations (commonly abbreviated as Dec, DEC or dec). Just like
Latitude, declination is measured in degrees, minutes and seconds north (positive) and south
(Negative), with 60 minutes in each degree and 60 seconds in each minute of declination. The
Celestial equator is 0 degrees declination, and the north and south celestial poles are +90 and -90 Degrees.
Measurements east and west on the sky are called right ascensions (commonly abbreviated RA,
R.A.). RA is measured in hours minutes and seconds of time. The reason for this is the sky turns
Once a day to the west as the earth rotates to the east. The celestial sphere moves one hour of RA
west per hour of time and 24 hours of RA during the course of the whole day. Since this is a
360-degree rotation, one hour of RA is equal to 15 degrees of turning (360/24 = 15). Otherwise, just like lines of longitude, RA lines are also great circles converging on the north and south celestial poles.
Longitude has the Greenwich meridian as the zero line dividing east and west. On the sky, the zero meridian in RA is labeled 00h00m00s. It intersects the celestial equator at a point called the vernal equinox (where the sun crosses the celestial equator in late March of each year).
These are the basics of the celestial coordinate system. They relate to your telescope because,
It uses these coordinates to find objects in the sky just like latitude and longitude are used to find cities, mountains and towns on the earth.
At this age and time of modern technology when man sends astronauts to space, sighting a new crescent shouldn’t be a big challenge.
Modern technology is used to compliment and aid sighting of the crescent by the naked eye (Islamically the crescent has to be sighted by the naked eye).
SIMWAL USMAN JIBRIL
Member Islamic crescent observation project Abu Dhabi UAE www.icoproject.org
Member National Moon sighting committee, Nigerian Supreme council for Islamic Affairs Abuja Nigeria.
Member Islamic research and timing organization Kaduna Nigeria (Producers of Timing Committee Islamic Hijri Calendar).
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