April 7, 2021

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One Crater's Rays

Originally published August 19, 2011 LPOD-Aug19-11.jpg
image by Howard Eskildsen, Ocala, Florida

All rays have sources, but they are not all easy to find. Nectaris is actually a rayophiles dream for there are many rays from known and unknown sources, and there are more ray types than have ever been classified. Lets start the tour with rays probably associated with Theophilus, the large crater near the center. To the north, across Sinus Asperitatis, are very narrow, tightly spaced rays that are not radial to a central point in Theophilus but seem to extend from the entire 110 km diameter of the rim. To the east there are three or so rays that do radiate from the center of the crater and widen with distance from the crater - these are fairly normal. To the southeast, past the two dark halo craters, are very weird, perhaps unique rays. There is a general pattern of brightness, possibly extending from Theophilus, but within it are narrow dark lanes. They may simply be places where mare shows between thin bright rays, but they look more like the dark material forms a deposit. In the middle of the length of these dark rays there is a perpendicular bright ray (probably from Tycho), and the dark rays are at their widest there and they narrow in both directions. Strange. It is much harder to see rays draped over highlands, but there is not much evidence for rays to the south or west of Theophilus. Was it formed by an oblique impact with the projectile coming from the southwest? That is generally consistent with the impact melts being to the north of the crater. As Howard wrote when submitting the image, this area really needs a lot more study.  :-)

Chuck Wood

Technical Details
2011-07-12, 01:32 UT. 6" F/8 refractor with Explore Scientific lens + 2X barlow + V-block +
IR block filters + Losmandy GM8 mount + JMI electronic focuser + DMK 41AU02.AS camera.

Related Links
Rükl plate 47


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Tomorrow's LPOD: Touch the Moon


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