[Friends_of_SSASTROS] Notes From the Field - Post Lawson Tower

[Mike McCabe]

Greeting Members and Friends of the SSAStros,
If you missed the event at Lawson Tower last night, you missed a big deal! We'll go into more detail at the meeting, but let's just suffice to say it was our best attended outreach event so far this year - by far!  
Even though I was feeling the wear and tear when I got home last night, that marvelous sky just refused to let up and it absolutely beckoned to be observed. While sitting out under the moonlight, beverage and snack at hand, the incredible conjunction between the Moon and Jupiter just drew me in like a magnet. It was actually the second one between the duo in less than a month's time, and both of them were spectacular.
On the 1st of October the waning gibbous Moon and the King of the Planets got together in the sky for a tango. As often happens, passing clouds will create a ring of irridescent colors around very bright objects in the sky, also known as a corona. In this image the Moon and Jupiter are rising through my eastern treeline, with Jupiter situated a little south and west of the Moon. Taken with my Samsung A71, Pro Mode, ISO3200, 1/20sec.

The King and La-Luna coupled up again on the 28th, with Jup switching sides this time and lying south and east of Jupiter. Again, passing clouds created a corona around the Moon. Samsung A71, ISO1600, 1/60sec.
Of course all this gandering at Jupiter got me curious, so I pulled it up in my Stellarium Plus Mobile app and sure enough there was something cool going on. The Galilean Moon Io was transiting the face of the planet, its shadow narrowly preceding it. Note how close the moon and the shadow are. That's because we're closing in on opposition very rapidly - it happens this coming Thursday - when the moons can't cast a shadow visible to us due to the straight alignment between the Sun, us, and the planet. That's just cool stuff!

My old home-built 4.5" Newtonian reflector deploys literally in seconds - that's a big bonus when you've got one foot in the bed already - and it has quality optics. It rendered that shadow absolutely marvelously in the now-steady seeing as we neared the witching hour. Our sharp-eyed readers may have noticed the in the Stellarium screenshot, the GRS on the incoming limb of Jupiter. That's a lot harder to resolve in a live visual view when it's in that position, so I can't say that it was definitively seen, and neither was Io itself, no matter how hard I tried.


I've said many, many times that it doesn't matter when you look at the Moon, there's always something special to see, and so it was last night. Mare Smythii, or the Sea of Smith if you will, is located on the eastern limb and part of it actually straddles the far side a little. Thus, it is rarely seen in its entirety. The libration last night was favorable though, and I could see the far rim of the see highlighted along the very edge of the incoming terminator. Image taken through the eyepiece at a power that I can't remember, but was probably 150x or higher, Samsung A71, ISO250, 1/1000sec.
If we do a little fancy math, or maybe even not so fancy, we can use the size of the basin coupled with the longitude of 87° at its center, and calculate that the far rim we were seeing last night lies at about 92.4°, so a couple of degrees on the far side. There's no black magic or hocus pocus at work here. That's perfectly normal for the Moon's well known wobble - aka libration - throughout the course of its motions. Image courtesy of a Virtual Moon Atlas screenshot. If you're a fan of the Moon, you need that software.
Until the sky clears again...
Sincerely,
Mike McCabe


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