IWLOP #074 - Arzachel

Arzachel is a spectacular Imbrian Era crater with sharply defined, deep-terraced walls. It makes a nice trio with Alphonsus and Ptolemaeus to the north.

Location: 18.2 S 1.9 W    Origin: Impact     Size: 97 km     Rukl: 55     Type: Complex Crater (CC)

Objects: Arzachel, Arzachel E & F, Alpetragius, Thebit & Thebit A

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: Arzachel had an off-centre peak, broad wall, and two valleys in shadow. The depression valleys E and F on the southeastern and southwestern walls were in the shadows and not easily seen, even at this magnification.
R2: Alpetragius had its crater floor seemingly filled with a volcano-looking peak.
R3: Thebit and Thebit A were to the southwest of Arzachel. The smaller Thebit A had impacted near Thebit's NW rim.

C1: The low hills on the south and southwest floor of Arzachel were observed.
C2: The accurate rille was noticed because its shadow was darker than the shadow cast from the rim onto the crater floor.

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