Maximum libration in longitude - 7 deg. 45 min.
Maximum total libration from earth's centre - 10 deg. 16 min.
Maximum diurnal libration - 1 deg. 1 min. 28.8 sec.
Angle subtended by one degree of selenographical latitude and longitude at the centre of the moon's disc, when at its mean distance - 16.566 sec.
Length of a degree under these conditions - 18.871 miles.
Selenographical arc at the centre of the moon's surface, subtending an angle of one second of arc - 3 min. 37.31 sec.
Miles at the centre of the moon's disc, subtending an angle of one second of arc - 1.139
[It must be remembered that this value is increased, in departing from the centre, in the proportion of the secants of the angular distance from the centre.]
Period of similar phase - 59 d. 1h. 28m. = 2 lunations.
Or, more accurately - 442 d. 23 h. = 15 lunations.