A sub-Rukl night on the moon

by David Kingsley


My 9 year old son had a friend sleep over last night, and I set up the scope to have them take a quick look at Jupiter and Saturn. There was lots of naked eye twinkle to the stars at 8 or 9 o'clock, and the views weren't too steady. By midnight however, long after the kids had gone to bed, the star twinkle had decreased a lot, and seeing was suprisingly good for this time of year. I found I could hold pretty steady images up to 360X or so in the 7 inch Starmaster Dob.

I took advantage of the reasonably steady conditions to roam around the moon a bit. Petavius was near the terminator and showed wonderful detail in the rimae along its floor and around its central peaks.

Nearby, I had a great view of Messier and Messier A, two nearby small craters with dual bright rays. Messier A itself cleary resolved into two superimposed smaller craters with much more detail than I have seen in this area before. I was impressed enough with the view to sketch a number of features in a surrounding region. When I then went in to get my Rukls moon atlas, I found I had diagrammed at least 9 more small craters in the 2 degree square around Messier/Messier A than could be seen in the Rukl map of the same area. Messier and Messier A are also featured in Rukl's "Fifty Views of the Moon" section, with accompanying photographs of the region. Eight of the nine small craters missing in the Rukl drawing were clearly visible in the photograph of the area, though I had seen them more clearly through the eyepiece than the photograph.

I also roamed up to crater Plato and found 6 craters in the relatively smooth floor of the brightly illuminated region. Pretty good for a night I had nearly written off as another twinkly night in December.

The Rukl atlas is a great guide that often shows me more than I can see through the scope. Last night however, the scope, seeing, moon position and illumination were good enough for some sub-Rukle views of the moon. If any of you are going to be up late assembling toys, wrapping packages, entertaining friends, or otherwise enjoying the holidays, take a look at the skies late at night. You may be suprised at what you can see once the skies have settled down after midnight.

Happy holidays to everyone and best wishes for a new year,