IWLOP #117 - Mons Gruithuisen Gamma (ϒ) & Delta (δ)

IWLOP #117 - Mons Gruithuisen Gamma (ϒ) & Delta (δ)

Impressive twin-shield volcanoes on boundary between Mare Imbrium and Oceanus Procellarum.

Objects: Mons Gruithuisen Gamma (ϒ) & Delta (δ), Mairan T, Sinus Roris, Mairan

Observation #1:
Location: Home
Date: 2021-06-20
Time: 10:45 PM ADT
Equipment: 10" Meade SCT
Eyepiece: Explore Scientific 4.7mm with 82° FOV
Magnification: x530
Seeing: Excellent (1) 
Transparency: Very Good (2)

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.

Observation #2:
Location: Home
Date: 2025-10-03
Time: 11:20 PM ADT
Equipment: 10" Meade SCT
Eyepiece: 10 mm (SvBony 10-30mm Zoom eyepiece)
Magnification: x250
Seeing: Excellent (1) 
Transparency: Very Good (2)

C1:  Easily identified the summit crater on Mons Gruithuisen Gamma. C2: Mairan T was found immediately beside the terminator, close to but detached from the peninsula containing Mairan. It was a surprise when I found it! Seemingly triangular in shape with a summit crater creating on a shadow on T's peak. There appeared to be lines of low hills on the Mare floor; there was a ridge creating a shadow from the mountains adjacent to these structures.