October 2, 2012
image by George Tarsoudis
George's image is a wonderful low light view of ridges throughout Mare Nubium. As I looked to see if any of the ridges marked buried craters I noticed a possible Lamont-type partial double ridge ring just south of Nicollet near top right. But then I saw the diagonal line crossing the Lamont-type feature. Following the trend to the west-southwest toward the terminator it becomes, with a slight offset, a rille-like feature. The "rille" parallels the Hesiodus Rille near bottom left. A quick check of the LRO QuickMap shows no evidence of the "rille" or the linear features near Nicollet. Of course, the QuickMap mosaic has a much higher illumination angle so low relief features would be harder to see. So is this alignment an artifact, perhaps where individual frames were mosaicked together, or is it a true feature on the lunar surface? The parallelism of the"rille" and the Hesiodus Rille suggests that the linear features are real, but the straightness, especially at top right is suspiciously like an artifact. George can tell us if this is a join line, but other observers with low Sun images of the area may want to check them.
Update: George reprocessed this mosaic and the linear features disappeared, consistent with Patricio's Comment. This LPOD was NOT meant to criticize George but to discuss the difficulty of interpreting features at the edge of resolution. This was a significant problem over a hundred years ago when a scientist interpreted photographic grain and defects as features on the Moon. As photography and its limitations became better known that misinterpretation problem mostly disappeared. But anything at the limits of detectability must be looked at carefully, as this LPOD tried to demonstrate.
Telescope Newtonian 10 inch @f/6.3, camera Unibrain fire-i 785, filter Red, barlow 3X, mosaic 4 images.
Rükl plate 54
See George's entire mosaic of Nubium here.
Yesterday's LPOD: Whitewashed!
Tomorrow's LPOD: A Rille Draped Across the Landscape