Notes From The Field - Short but Sweet

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Apollo XX
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Notes From The Field - Short but Sweet

Unread post by Apollo XX »

June 10th, 2022 – Early Evening;

The SSAS group had a group observing session on the schedule for this evening, but with the threat of haze and even outright clouds occupying the sky the airwaves remained silent throughout the day. As is often the case though, the sky was quite workable for at least some of the time in the evening, especially if all you wanted to look at was the Moon. When I looked up at the sky just prior to sunset the Great Orb of Green Cheese was a quite vividly 84% illuminated in a waxing phase, and past experience has shown me that many fine sights can be discerned along the terminator at that stage of illumination. I slung a shoulder under the old AR6 which was mounted on an AstroTech Voyager Alt/Az mount and walked it out to the lawn.

Given that it was still pre-sunset the sky was still quite bright and blue, but it was also obviously transparent so I dropped in a 9mm eyepiece which gives me 133x in that scope and began my tour. One thing that became apparent straight-away was that the seeing was steadier than usual for this time of day, as anyone who has wielded a telescope on the sky around the evening twilight hours can tell you the transition period from day to night is usually quite unsteady as the air temperature drops and the heat of the earth rises up into the sky. Apparently we would be defying basic physics on this evening, and that was fine with me.

My first sweep along the terminator revealed several prominent features displaying themselves, including the crater Gassendi on the north shore of Mare Humorum, the crater Aristarchus on the very edge of the terminator, the crater J.Hershchel just inboard of the northwest terminator, and the crater Philolaus lying at a latitude of 72.1° north.

The primary attraction of Gassendi is a series of valleys that strafe the lava-filled interior in all directions around the central peaks. These rilles become nicely highlighted during favorable illuminations.

GassToHes.png (491.04 KiB) Viewed 135 times
Gassendi sits atop the lunar sea Mare Humorum, aka the Sea of Humidity, while Hesiodus A is much further inland and was under a much higher sun angle, which seemed to make resolving the concentric crater easier.

The crater Aristarchus is a tough study, primarily because it possesses the highest albedo of any feature on the moon and that brightness produces a glare that tends to wash out details. Even on this evening when the terminator was virtually hugging the crater, the illuminated interior wall was virtually whitewashed with sunlight.

J. Herschel is interesting in the sense that it is very broad, very flat, and very tortured. Under good lighting there are a lot of details to be gleaned from this feature. It’s an object that often seems to ‘pop’ in the eyepiece during the late waxing phases of the moon cycle.

Several craters of the higher northwest region of the moon also seem to display themselves well during the later waxing phases, and Philolaus is often one of them. It’s always interesting to see an object in near-profile that has a significant depth to it, and at 10k+ feet deep, Philolaus falls into that category.

PhilPlatJHersch.png (632.71 KiB) Viewed 135 times
The northwest quadrant of the moon is a fun place to explore during the waxing phases. The seeing on this night allowed the resolution of the two marked craterlets in Plato, which more often than not is not possible due to unsteady seeing.

Of significant note during this observing session, the seeing was good enough to support the resolution of two of the tiny craterlets in Plato, and the concentric ring in Hesiodus A. It was a very good if only short lunar observing session.

HesA.png (444.07 KiB) Viewed 135 times
A few of us have been having tons of fun with Hesiodus lately, which under favorable illumination sports a sunlight ray streaming across it, but the concentric ring in Hesiodus A is resolvable on a more frequent basis. The view shown in this image resembles a completely impractical magnification not even remotely possible with earth-based observing equipment. You can expect it to be relatively tiny even at powers of 200x+.

Keep Looking Up! Mike McCabe
"The purpose of life is the investigation of the Sun, the Moon, and the heavens." - Anaxagoras
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Re: Notes From The Field - Short but Sweet

Unread post by AstroGeek »

Nice report, Mike.
I was out there again, trying to catch an image of Hesi-A
Results to be revealed at the Cosmic Coffeehouse on the 15th
Steve l.
Steve L
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