IWLOP #075 - Ptolemaeus & Alphonsus

Very prominent craters easily visible through binoculars. Older Ptolemaeus (pre-Nectarian) and younger Alphonsus (Nectarian) are visible on the terminator at the same time. Ammonius, located on Ptolemaeus' floor, is one of only a few named craters within a larger one.

Location: 12.0 S 2.0 W    Origin: Impact    Size: 153 km (Ptolemaeus), 110 km (Alphonsus)    Rukl: 44    Type: Complex Craters (CC)

Objects: Ptolemaeus, Alphonsus, Herschel, Ammonius, Flammarion, Rima Flammarion
Identified Others: Glyden, Mosting, Mosting A, Spörer

Observation 1:
Location: Home

Date: 2018-09-17
Time: 9:30 PM ADT
Equipment: 10" Meade SCT, 10 mm eyepiece + x2 Barlow
Magnification: x500
Seeing: Very Good (4)
Transparency: Good (3)

R1: Alphonsus' central peak was located adjacent to a rise or rille. 
R2: Ptolemaeus has a smooth floor and the small circular crater Ammonius was located; it had no noticeable shadows on Ptolemaeus' floor. 

Observation 2:
Location: Home

Date: 2021-03-22
Time: 9:30 PM ADT
Equipment: 10" Meade SCT, 4.7 mm eyepiece 
Magnification: x530
Seeing: Very Good (4)
Transparency: Good (3)

R1: Herschel is north of Ptolemaeus and is quite deep by comparison, and is especially deeper than the shallow Spörer to its north.

C1: There are three distinct dark patches in the NE, SW and SE. 
C2: The crater Flammarion has a break in its southern rim; the northern rim is non-existent. Rima Flammarion began at crater C and headed north of Mosting A through a valley in its rim.

NOTEResearch conducted after this session indicated the dark patches were ash deposits from fire fountains that ocurred after Alphonsus was formed. 



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