Crescent Visibility 2019

  • The term ‘New Moon’ means when the moon has gone through all its phases and is approximately at the same longitude as the sun. This is know as conjunction
  • From one conjunction to next conjunction occurs around 29.5 days and is known as the lunar month
  • At conjunction, it is impossible to see the moon
  • By using astronomical calculations, it is possible to calculate precisely when conjunction occurs
  • What is more difficult to calculate, is the actual visibility of the new moon by the unaided eye
  • We as Muslims are interested in this sighting, because it was the practice of the Holy Prophet Muhammad (peace and blessings of Allah be upon him) to determine the beginning and ending of the month of Ramadhan by sighting the moon with the unaided eye
  • The thin crescent visibility is dependent on several factors, such as: –
    1. The age of the moon – generally the age of the moon should be at least 22 hours
    2. How far the moon lags behind the sun before it sets. The greater the ‘lag time’ after the sun has set, the better the chance of witnessing the new moon
    3. Of course, if the moon sets before the sun, it will not be possible to view the moon!
    4. The altitude of the moon is how high the moon is above the horizon at sunset. The higher the altitude the greater the chance of visibility
    5. The moon azimuth is how many degrees along the horizon with 0 degrees being North. The important factor is the delta azimuth – i.e. the difference between the sun and the moon on the horizontal plane
    6. The angular separation – or the elongation – between the sun and the moon. This is one of the most important factors
    7. It is not possible to see the moon, even with a telescope if the elongation is around  7 degrees
    8. This limiting factor is known as the Danjon limit
    9. For unaided eye, elongation must be at least 12-15 degrees, but much will depend on other factors also being favorable, for example lag time, age of the moon, altitude etc
    10. Atmospheric conditions – on a cloudy day it will not be possible to see the moon
  • Many crescent visibility criteria have been developed over time and they have become reasonably accurate
  • A criteria developed by Dr Brian Yallop, known as the Yallop’s criteria has proved to be one of the most reliable
  • Yallop’s criteria has been adopted by H.M. Nautical Almanac Office. The visibility maps shown below are based on calculations from Yallop’s criteria

Moon Calculations May/June 2019

Date Moon Age Moon Alt Moon Az Sun Az Moon Set Sun Set Lag time Code
h:mm deg deg deg h:mm h:mm mins
05/05/2019 20:44 4 288 298 21:04 20:30 34 F
06/05/2019 44:46 14 281 299 22:17 20:32 106 A
03/06/2019 10:08 0 303 309 21:13 21:10 3 F
04/06/2019 34:09 8 294 309 22:17 21:11 72 A
A Easily visible
B Visible under perfect conditions
C May need optical aid to find the crescent Moon
D Will need optical aid to find the crescent Moon
E Not visible with a telescope
F Not visible, below the Danjon limit

Saturday, 4th of May 2019

Moon is not visible anywhere in the world. Most of the world is Red – i.e. moon sets before sun, so therefore will be impossible to view.

The purple area in South America is the old moon – conjunction has not occurred yet

Sunday, 5th of May 2019

Moon can be visible in parts of North and South America. However it can also be visible in most of Africa but may need the help of a telescope.

Therefore, for Asia, Europe and most of Africa, moon is not yet visible by the unaided eye

Monday, 6th of May 2019

Most of the world is now covered in Green (A – easily visible to the unaided eye)

Therefore the following day, i.e. Tuesday 7th of May is the 1st of Ramadhan for Asia, Europe and most of Africa

Monday, 3rd of June 2019

The moon is not visible anywhere in the world, except in some small islands to the west of America

Tuesday, 4th of June 2019

The moon is easily visible to the unaided eye in most of the world.

Therefore, Wednesday 5th of June will be the 1st of Shawwal.

Eid ul Fitr will inshaAllah be on Wednesday 5th of June.


References

Data: http://astro.ukho.gov.uk/psp/index_beta.html
Visibility maps:  http://www.staff.science.uu.nl/~gent0113/islam/islam_lunvis.htm
Yallops Criteria: http://astro.ukho.gov.uk/download/NAOTN69.pdf
Moon Watch: http://astro.ukho.gov.uk/moonwatch/