Assume that the solar eclipse is witnessed towards the end of the 27th day of the Islamic month - for example, 26.9 days after the sunset which marked its start.

The time elapsed since the birth of the previous New Moon has to be approximately 29½ days. Of course, that time-interval can be ‘squeezed down’ slightly if desired. (However, a shorter lunation also means a fast-moving moon (see below*) - which negates the ‘advantage’ of deliberately selecting a short month in order to try and make a 27th-day eclipse look more feasible). The diagram above illustrates a value of 29.4 days.

Simple arithmetic shows that the new Islamic month would then have commenced about 2½ days after New Moon birth.

In other words, no sighting would have been made 1½ days after conjunction. It is worth adding that lack of success here is more likely if the New Moon is migrating comparatively slowly. *However, it tends to travel faster than normal whenever the lunation is particularly short (because those circuits are always associated with New Moon occurring near perigee).

Lunar latitude will not be all that great at the beginning of the month (because an eclipse will shortly take place), so in these circumstances the latitude factor will not drastically prejudice the prospects for crescent-sighting.

Thus, if the Ahmadiyyas wish to regard the 27th as one of their ‘possible days’ for a solar eclipse, then they will have to recognise that 36-hour crescents will sometimes not be spotted (from a specified location, admittedly). Therefore, they will also have to accept that lunar eclipses can occasionally occur on the 12th of their Islamic month. (This last phenomenon is discussed in detail in the correspondence file.)

[Diagram also scanned in at http://dlmcn.com/qad27.jpg]

David McNaughton
Home Page: http://dlmcn.com