IWLOP #065 - Hipparchus

A pre-Nectarian crater with badly disintegrated walls and square-like shape, perhaps due to pre-existing faults.

Location: 5.5 S 4.8 E    Origin: Impact     Size: 150 km     Rukl: 44, 45     Type: Complex Crater (CC)

Objects: Hipparchus, Horrocks, Halley, Hind, Seeliger, Reamur
Others Identified: Albategnius, Airy, Argelander, Hipparchus C, Hipparchus L, Klein, Oppolzer, Pickering, Sinus Medii, Vogel


Observation 1:
Location: Home

Date: 2019-04-11
Time: 11:52 PM ADT
Equipment: 10" Meade SCT
eyepiece: 10mm

Magnification: x250
Seeing: Very Good (2)
Transparency: Excellent (1)

R1: Hipparchus had a smooth floor except for what appears to be two ghost craters plus craters N and X. Crater N was central on the floor whereas Crater X looks to have impacted the wall.
R2: Horrocks was inside the N-NE wall. Halley was on the west wall whereas Hind and crater C were outside.

C1: I referred to the two buried craters as ghost craters (refer to R1)
C2: 
Seeliger and Réaumur were beyond the terminator in darkness during this session.

NOTE: Also identified Pickering outside the wall near Horrocks.

Observation 2:
Location: Home

Date: 2025-10-11
Time: 6:05 AM ADT
Equipment: 10" Meade SCT
eyepiece: 10mm

Magnification: x250
Seeing: Fair to Good (4-3)
Transparency: Excellent (1)
Temperature: 4° C, light wind picking up during this session that began at 5 AM.

R2: The curved line of three craters - Hind, Hipparchus C and Hipparchus L - just outside the crater walls assisted in identifying Hipparchus. Hind was the largest and L was the smallest. Round Horrocks was easily found, its walls brighter than Hipparchus's floor and its floor in shadow.

C2: Seeliger was very small, cup shaped, and had very bright walls. It was located in a flat area that was lighter in colour than Sinus Medii to its north. Réaumur's walls were heavily eroded especially in the north adjacent to the Sinus Medii; its floor was smooth with no discernible features. Its NW wall was shared with the barely visible crater Oppolzer (ghost crater almost).