Yesterday on a walk in Hawk Ridge Nature Reserve near my home, a flock of migrating nighthawks blew by headed south. I identified them right away by their white wing patches. Birds on the move, cool mornings lavish with dew. I like these hints of fall. Through the telescope last night, the nearly 12-day-old moon served as an illuminated stage for the passage of yet more birds. Over a period of five minutes, I saw some a dozen silhouetted avians zip across the cratered landscape on their way outta here.
Now through September is an ideal time to point your telescope at the waxing moon — especially around full phase — to watch birds migrate at night. We don’t think about it much, but many birds are busy migrating while you and I are out like a light. Hummingbirds, warblers and others not only avoid the heat of day by doing so but are less likely to get nailed by a predator under cover of darkness. To watch the show, all you need is a small telescope and a big moon. Plunk in your low power eyepiece and just wait. I saw my first bird within a minute. They fly by quickly, but since I’m no bird expert, I couldn’t identify the different species. Craters are my forte.
Some amateur astronomers scorn gibbous and full moons as worthy of study because they’re too bright, and the landscape is washed out due to the sun shining almost directly above the moon’s surface. When the sun shines from the side, as it does near sunset and sunrise both here and on the moon, everything casts a shadow and shows minute detail. Every bump, wrinkle and hair on a person’s face stands out in glaring detail. But shine a light directly at a person’s face – equivalent to the sun shining squarely over the full or nearly full moon – and shadows and those disturbing wrinkles disappear, lost in a flood of light.
A full moon offers no sense of depth or relief, but does reveal details otherwise invisible at other lunar phases. That includes many small craters which hardly anyone notices during lesser phases, but which are transformed into brilliant rings during the equivalent of lunar high noon. Last night I lost count of how many of these “hot rings” I saw through the telescope at low power. They’re so brilliant they resemble white flares or fiery white-hot rings of lava. Johnny Cash’s “Ring of Fire” comes to mind.
What you’re seeing is high-angle sunlight reflected off fresher rocks and soils on crater rims and floors or from the tendrils of long rays (splashed rock) surrounding fresher craters. The rays and lighter soils truly shine around the time of full moon. Once you get into seeing these strange lunar lily pads, you’ll be surprised at how alien they look compared to the more familiar peaks and crater holes seen to advantage at other phases.
I was particularly struck by the fiery ring of Proclus crater and its peculiar off-center system of rays. Proclus, at 18 miles in diameter, is a young lunar crater, and the brilliance of its rim is clearly the result of fresh rock exposed by impact that has yet to darken under the influence of solar radiation. It contrasts beautifully with the older, surrounding moonscape called Palus Somni or the Marsh of Sleep. The weird forked appearance of the rays suggests that the asteroid that created Proclus struck the moon at an oblique angle.
Other brilliant craters and ray systems include Aristarchus (brightest crater on the moon) and Tycho, and there are many more. Like Proclus, they’re relatively fresh craters compared to most. With binoculars you can see all three of the aforementioned as bright spots, while any telescope will show their ring-like forms and feathery rays in far more detail. Between moon and birds, you may find yourself staying at the telescope side later than you thought tonight.