alos90
Method to return alos (dawn) calculated using 90 minutes before sea level based on the time to walk the distance of 4 Mil at 22.5 minutes a Mil.
Time based offset calculations for alos are based on the opinion of the Rishonim who stated that the time of the Neshef (time between dawn and sunrise) does not vary by the time of year or location but purely depends on the time it takes to walk the distance of 4 Mil.
Return
the Date representing the time. If the calculation can't be computed such as in the Arctic Circle where there is at least one day a year where the sun does not rise, and one where it does not set, a null will be returned. See detailed explanation on top of the AstronomicalCalendar documentation.