IWLOP #073 - Regiomontanus & Purbach

Regiomontanus is a pre-Nectarian Era crater. Note it's severely eroded walls and elongated shape. Purbach is a prominent pre-Nectarian Era crater with a poorly defined and eroded western wall.

Location: 28.4 S 1.0 W    Origin: Impact     Size: 126x110 km (Regiomontanus), 118 km (Purbach)    Rukl: 55     Type: Complex Craters (CC)

Objects: Regiomontanus, Purbach


Observation 1:
Location: Home

Date: 2018-09-17
Time: 7:40 PM 
Equipment: 6" Dobsonian, 10 mm eyepiece
Magnification: x120
Seeing: Very Good (2)
Transparency: Good (3)

R1: Regiomontanus was located north of Walther. Regiomontanus A was located on its north floor. At x120 magnification, the centre peak was a little off-centre and a few crater-like formations comprised the terrain of that area. Regiomontanus appeared lower in elevation than did Walther.
R2: Purbach had ridges highlighted on the one side and tall shadows on the other. Crater G had certainly impacted its northern rim. At the north end of Purbach, the shadows showed like two lines (not straight) going from near the rim to almost the centre. Wasn't sure if it was craters on the floor.

Observation 2:
Location: Home

Date: 2021-04-19
Time: 8:30 PM 
Equipment: 10" Meade SCT, 4.7 mm eyepiece + x2 Barlow
Magnification: x1060
Seeing: Good (3) - Fair (2)
Transparency: Very Good (4)

The line of craters on Purbach's floor is what caught my attention, in combination with the line of craters in Regiomontanus.

NOTE: The shadows that showed like two lines going from near the rim to almost the centre in the previous observation may have been the east and west walls of the craters on the floor.

R2: Purbach's north wall was either terraced quite well or was slumped (?). Crater G was completely in shadow on its floor; its impact on Purbach's north wall was substantial. Tonight there appeared to be 2 shallow craters in a line southward from G above crater W; small crater A was below and in line with them. Two craters (U and S) impacted the south wall. Didn't see this detail in 2018.


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