Terminator Crossing Hipparcus
I've had several questions from people wondering what I'm talking about when I mention the "terminator." Contrary to popular belief, the terminator isn't a killer robot. It's the line between day and night on a planet or other natural orbiting object. On Earth, we experience the passing of the terminator as sunrise and sunset, but someone watching from the vantage point of the moon would see the line of light/dark, the terminator, slowly crossing the place where we were standing.
In this shot the terminator has reached the middle of Hipparcus and Albategnius. Their central peaks are all that remains poking up high enough for the sun to still strike them. This condition will only last for a few minutes, and those peaks, too, will be plunged into the fourteen-day long lunar night.
A few hours after this photograph, the terminator made its way across Ptolemaeus, Alphonsus, and Arzachel, and then began its march across Mare Nubium. The terminator is very interesting, both photographically and geographically, because the extremely low sun-angle creates shadows and highlights that reveal very subtle features in the terrain. Rupes Recta is a good example of this. The "Straight Wall" is all but invisible except when the sun is within a few degrees of the the lunar horizon. As the sun sets, it illuminates the slope, revealing its presence as a line that's brighter than the surrounding terrain. When the sunrise terminator is nearby, the rising sun leaves the slope in shadow, distinguishing Rupes Recta as a dark slash dividing the flooded, ruined crater beneath it.
I've taken the time to label most of the major features in this picture. This is one of my favorite spots on the lunar surface. I never tire of looking at it!
Terminator Crossing Hipparcus
I've had several questions from people wondering what I'm talking about when I mention the "terminator." Contrary to popular belief, the terminator isn't a killer robot. It's the line between day and night on a planet or other natural orbiting object. On Earth, we experience the passing of the terminator as sunrise and sunset, but someone watching from the vantage point of the moon would see the line of light/dark, the terminator, slowly crossing the place where we were standing.
In this shot the terminator has reached the middle of Hipparcus and Albategnius. Their central peaks are all that remains poking up high enough for the sun to still strike them. This condition will only last for a few minutes, and those peaks, too, will be plunged into the fourteen-day long lunar night.
A few hours after this photograph, the terminator made its way across Ptolemaeus, Alphonsus, and Arzachel, and then began its march across Mare Nubium. The terminator is very interesting, both photographically and geographically, because the extremely low sun-angle creates shadows and highlights that reveal very subtle features in the terrain. Rupes Recta is a good example of this. The "Straight Wall" is all but invisible except when the sun is within a few degrees of the the lunar horizon. As the sun sets, it illuminates the slope, revealing its presence as a line that's brighter than the surrounding terrain. When the sunrise terminator is nearby, the rising sun leaves the slope in shadow, distinguishing Rupes Recta as a dark slash dividing the flooded, ruined crater beneath it.
I've taken the time to label most of the major features in this picture. This is one of my favorite spots on the lunar surface. I never tire of looking at it!