IWLOP #117 - Mons Gruithuisen Gamma (ϒ) & Delta (δ)
Impressive twin-shield volcanoes on boundary between Mare Imbrium and Oceanus Procellarum.
Location: 36.3 N 40.0 W Origin: Volcanic Size: 20 km each Rukl: 9 Type: Domes
Objects: Mons Gruithuisen Gamma (ϒ) & Delta (δ), Mairan T, Sinus Roris, Mairan
Time: 10:45 PM ADT
Equipment: 10" Meade SCT, 4.7 mm eyepiece
Seeing: Excellent (5)
Transparency: Very Good (4)
R1: The two domes stood out as bright, white entities like sentries standing guard at the entry to some highlands/craters. Delta wasn't as bright as Gamma but Gamma was tall enough to cast a shadow on Delta. Delta appeared elongated compared to the rounded Gamma. Tall shadows created by both.
The crater Gruithuisen appears round with a bright rim. Upon closer examination, I realized a small crater had impacted the rim, giving me the false initial impression of a deteriorated wall.
C1: Could not see the summit crater on Mons Gruithuisen Gamma.
C2: Most of Mairan was in shadow. Mairan T was beyond the terminator.