Cloud-filled skies again these past few nights, so I had a rummage through my archives and found this video capture of the moon's surface which I did last September. In fact, the first time I'd used my newly-purchased CCD imager with my telescope and was just a test. Still, a few interesting lunar features of note to see in the video.
In the first half of the video above, you'll see that the lunar surface has patches of dark 'seas' - these are the lunar maria. They were dubbed maria, Latin for "seas", by early astronomers who mistook them for actual seas but they are actually large, dark plains of basalt rock, formed by volcanic eruptions in the moon's very distant past. They are less reflective than the rest of the moon's surface (as a result of their iron-rich compositions) and hence appear dark to the naked eye. The 'seas' you see in this video are Mare Humorum (Sea of Moisture) and Mare Nubium (Sea of Clouds)
Midway in the video, you will begin to see the rays of ejecta of an impact crater and the crater Tycho them comes clearly into view. Tycho Crater is about 85 kilometers across. The sharpness and 'freshness' of the crater and the rays of material radiating from it suggest that this is a young crater - there has been little time for it to be degraded by subsequent impacts. Based on analysis of samples of the crater ray recovered during the Apollo 17 mission, the impact is likely to have occured about 108 million years ago.
Towards the end of the video, we approach the "terminator" - the dividing line between the illuminated (day side) and dark (night side) of the Moon. Shadows and detail are most pronounced along the terminator, and you can see the lunar surface here is quite different - no expansive 'seas' or broad plains of ejecta rays but pock-marked with hundreds of small craters.
And on the subject of measurements, there is an excellent piece of software that allows you to make those measurements with images you take of the lunar surface. The Lunar Terminator Visualization Tool (LTVT) by Jim Mosher is a free software tool that allows you to make highly accurate measurements on lunar images, including drawing contours using digital elevation model (DEM) data and using those for analysing and interpreting crater shadow patterns. Cool stuff! You can dowload LTVT at http://ltvt.wikispaces.com/LTVT
In the first half of the video above, you'll see that the lunar surface has patches of dark 'seas' - these are the lunar maria. They were dubbed maria, Latin for "seas", by early astronomers who mistook them for actual seas but they are actually large, dark plains of basalt rock, formed by volcanic eruptions in the moon's very distant past. They are less reflective than the rest of the moon's surface (as a result of their iron-rich compositions) and hence appear dark to the naked eye. The 'seas' you see in this video are Mare Humorum (Sea of Moisture) and Mare Nubium (Sea of Clouds)
Midway in the video, you will begin to see the rays of ejecta of an impact crater and the crater Tycho them comes clearly into view. Tycho Crater is about 85 kilometers across. The sharpness and 'freshness' of the crater and the rays of material radiating from it suggest that this is a young crater - there has been little time for it to be degraded by subsequent impacts. Based on analysis of samples of the crater ray recovered during the Apollo 17 mission, the impact is likely to have occured about 108 million years ago.
Towards the end of the video, we approach the "terminator" - the dividing line between the illuminated (day side) and dark (night side) of the Moon. Shadows and detail are most pronounced along the terminator, and you can see the lunar surface here is quite different - no expansive 'seas' or broad plains of ejecta rays but pock-marked with hundreds of small craters.
This second video above takes a closer look along the terminator. The terminator is actually the best place to make lunar observations. The other illuminated surface on the moon, further from this line, appears almost flat, due to the dazzling light and the absence of shadows. However, at the terminator, we can see the shadows reveal the depth of the crater walls, the height of the mountain ranges and bringing other topographical features in sharp relief. Due to the angle at which sunlight strikes this portion of the moon, shadows cast by craters and other geological features are elongated, thereby making such features more apparent to the observer. This phenomenon is similar to the lengthening of shadows on Earth when the sun is low in the sky. For this reason, much lunar observation study centres on the illuminated area near the lunar terminator, and the resulting shadows provide accurate descriptions and measurements of the terrain.
And on the subject of measurements, there is an excellent piece of software that allows you to make those measurements with images you take of the lunar surface. The Lunar Terminator Visualization Tool (LTVT) by Jim Mosher is a free software tool that allows you to make highly accurate measurements on lunar images, including drawing contours using digital elevation model (DEM) data and using those for analysing and interpreting crater shadow patterns. Cool stuff! You can dowload LTVT at http://ltvt.wikispaces.com/LTVT
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