misheyakir7Point65Degrees
This method returns misheyakir based on the position of the sun when it is 7.65˚ below geometric zenith (90). The degrees are based on a 35/36 minute zman around the equinox / equilux, when the neshef (twilight) is the shortest.
Sources:
This time is based on Rabbi Moshe Feinstein who writes in Ohr Hachaim Vol. 4, Ch. 6) that misheyakir in New York is 35-40 minutes before sunset, something that is a drop less than 8.
Rabbi Yisroel Taplin in Zmanei Yisrael (page 117) notes that Rabbi Yaakov Kamenetsky stated that it is not less than 36 minutes before sunrise (maybe it is 40 minutes).
Sefer Yisrael Vehazmanim (p. 7) quotes the Tamar Yifrach in the name of the Satmar Rov that one should be stringent not consider misheyakir before 36 minutes.
This is also the accepted minhag in Lakewood that is used in the Yeshiva.
This follows the opinion of Rabbi Shmuel Kamenetsky who provided the time of 35/36 minutes, but did not provide a degree-based time.
Since this zman depends on the level of light, Rabbi Yaakov Shakow presented this degree-based calculations to Rabbi Kamenetsky who agreed to them.
Return
the Date of misheyakir. If the calculation can't be computed such as northern and southern locations even south of the Arctic Circle and north of the Antarctic Circle where the sun may not reach low enough below the horizon for this calculation, a null will be returned. See detailed explanation on top of the AstronomicalCalendar documentation.