Comparison of the lunar profiles of Watts and of Welmer.

Abstract

Direct comparisons are made between profiles of the moon’s limb of Weimer and of Watts. Comparison made at 177 points on the moon’s limb shows that Weimer’s centre deviates 0". 39 in the position angle of 336° from Watts' centre, while their adopted radii of the moon are practically identical. Another comparison is made at every 5° along the moon’s limb for 9 cases of libration, i.e. combination of ι= -6°, 0°, +6° and b＝十6°, 0°, -6°. Discrepancy between Watts’ and Weimer's charts differs for eastern and western limbs from each other as well as for libration. There exists no systematic dependence between relative positions of centres and libration. As a whole, Weimer’s chart deviates 0". 43 in the direction of 345° for eastern limb and 0". 27 in the direction of 296° for western limb from Watts'. The effect of the discrepancy between both charts in position of centre is found clearly in the difference of Δ T evaluated from occultation observations with these respective profile charts, and verifies that our values of Weimer’s centre relative to Watts’ are adequate,