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
Time: 9:30 PM ADT
Equipment: 10" Meade SCT, 10 mm eyepiece + x2 Barlow
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.