Why Is this Moon Not Visible?

A crescent moon’s first sighting depends on several interrelated factors. (For details see “Earliest Visibility Criteria” section.                       

Moon’s Age:

For a crescent moon to be visible its age should be around 24 hours, although the youngest sighted moon was only 14+ hours old. Often moon’s age may be 30+ hours but you cannot see it because its angle from the sun (elongation) and altitude (above the horizon) do not reach a minimum (12+10 degrees) visibility threshold.

Angle (Elongation):

For a naked-eye sighting the moon’s angle from the sun at sunset should be approx. 12 degrees.

Altitude:

Moon’s altitude at the sunset should be 10 degrees or more for a casual observer.

(Higher elongation may sometimes compensate lower (8+ degrees) altitude.

Moonset After Sunset:

You cannot see a faint crescent moon within the first ten minutes after the sunset when the time lag between the moonset and the sunset is less than 42 minutes. Usually a 29 days old moon will be visible 20-30 minutes after the sunset and a 30 days old moon will be seen after 10-12 minutes after the sunset.

Visibility Curve:

A crescent moon may first become visible from as far east as New Zealand or as far north as Japan, but it may not be seen in Saudi Arabia hours later. Moon’s visibility extends within a parabola and it takes 48+ hours to cover most of the globe.

Words of Caution:

Experienced professional moon-watchers may SEE a crescent moon at a little lower visibility threshold after meticulous preparation when the horizon is exceptionally clear. A good example was Sha’ban 1426 (Sep. 2005) moon from Arizona:

    Sunset (at sea level)   = 18:49                                     Moonset (at sea level)  = 19:30

    Age at  18:39 pm         = 31 hr. 50 min.                      Moon lag time             = 41 minutes

    Relative Altitude        = 8.45 degrees                        Elongation from sun   = 13.77degrees

    Crescent width           = 26     arcseconds                 Illumination                  = 1.44  percent

Casual Muslim Observers:

However, casual Muslim observers all over the world claim seeing moons that are “Impossible”. Naïve “experts” and Ulema accept their claim only because they are “Adil”. The results are disastrous. Eid al-Fitr on the last day of Ramadan, Eid al-Adha on 9^thD. Hijja and Ramadan on 28 Shaban.

If the earliest sighting is not by a large group and not confirmed from places located west of the first claim the “Shahadah” should be rejected as doubtful.