Moonwatch
W Bond
THE WALLED PLAIN W Bond is conspicuous for a number of reasons. First, its name is a little odd as lunar features don’t tend to include the initial of the person they are named after. In this case it’s named after William Cranch Bond, an American astronomer who, together with his son G P Bond, is credited as having taken some of the earliest photographs of the Moon. In the past it has gone under the name Bond and W C Bond.
As walled plains go, W Bond is also conspicuous because of its shape. Rather than the more typically round profile you’d expect, here we see a feature that’s decidedly rectangular. It’s an old feature and this has played a part in shaping it, its walls having been eroded and modified over time. However, through a telescope, its regular shape is quite striking.
The floor of W Bond looks relatively flat under high illumination but when the Sun gets low in the lunar sky, oblique lighting shows it to be quite bumpy and rough. There are a number of craters inside its rectangular rim, the most prominent of which is 15km W Bond B towards the eastern corner. Half the size again, 7km W Bond C lies 20km to the northeast.
These craters are a useful navigational tool to help you look for a curious rille that appears to run along part of the east-west diagonal of the rectangle. The rille is visible under good lighting conditions, but when the light comes from the wrong angle it disappears without trace. The best time to pick it up is during the waxing phase when the terminator is relatively close by – say around 60 per cent illumination. It’s in the late waning phases that the rille vanishes from view. As it’s a rather narrow feature, it best suits larger scopes or highresolution imaging setups.
The rugged floor of W Bond contrasts well with the flat lava of Mare Frigoris, which runs to the southwest, clipping the southern corner of W Bond’s perimeter. In fact the corner itself is marked by what looks like a lava-filled crater. This is Archytas B (36km wide). Compare its appearance with the similarly sized Timaeus (33km), which sits further northwest, in the middle of the southwest edge of W Bond. Whereas Archytas B appears completely flat, Timaeus is a more typical crater with a sharp rim and central mountain peak.
Epigenes (55km) sits just off the northwest of W Bond. It is a well-defined crater with a flat floor and offset central mountain. The wall dividing it from W Bond is pronounced, and on the other side sits 18km Epigenes A.
There is a peculiar regularity to the features in this part of the Moon. As an example, look at Barrow (93km) to the northeast of W Bond. It too has a certain rectilinear appearance, the southwest part of its rim almost parallel to the northeast edge of W Bond. This is a fantastic part of the Moon to study, especially when the Sun’s light is low and oblique, causing dramatic shadows to dominate the view.
“It’s an old feature, its walls having been eroded and modified over time”