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Old 04-05-2012, 12:32 AM
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mental4astro (Alexander)

mental4astro is offline
Join Date: Jun 2008
Location: sydney, australia
Posts: 4,960
A Lunar dagger, aka The Straight Wall, and Rima Birt

Thought I’d share this latest lunar sketch of mine. It was done a few weeks ago of the striking feature The Straight Wall.

I’ve seen this feature countless times since I pointed my first telescope at the Moon some 30 years ago. The Wall seems to be in a relatively featureless section of the Moon as it sits in Mare Nubium. This time, however, I noticed a few details that made me exclaim “WOW” all over again with the Wall. The orientation this time in the eyepiece saw its southern end at the top of my field of view. This end of the escarpment has a small mountain complex that makes it look like the handle and guard of a dagger, with the Wall as the blade.

Seeing wasn’t the best, but I also managed to spy out a tiny crater at the northern end of the Wall. Some research on it leads me to believe it is between 3 and 4km in diameter. Always astounds me to believe that such a tiny feature in the eyepiece is actually so big on the Moon. Much smaller features are visible, but conditions need to be better. Best I’ve been able to identify is in the half kilometre mark as the width of various rilles. One of those, despite the prevailing conditions, I did manage to see right next to the Wall, siting just west of it, Rima Birt. The crater Birt is the largish crater just west of the “blade’s” centre, and the rille heads north from it.

In the full sketch image the Rima Birt is difficult to see, which is why I added a close up photo of the sketch. Surprises me how neat the “tiny” gash came up! I am guessing that because Rima Birt is an extended feature that I was able to see it, while other features of the same width eluded detection.

Mare Nubium is not a featureless as I thought after all, !



Scope: Celestron C8, 8" SCT
Gear: 9mm TMB Planetary Type II, 222X
Date: 31st March, 2012
Location: Sydney, Oz
Media: White and grey pastels, black charcoal and white ink on A4 size black paper
Duration: approx. 2hrs
Circle diameter: 16cm
Attached Thumbnails
Click for full-size image (Straight Wall - Copy.JPG)
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Click for full-size image (Straight Wall, detail - Copy.JPG)
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