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Mare Humboltianum: The Peekaboo Basin

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#1 kraterkid

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Posted 11 May 2009 - 12:10 AM

Located in the far northeast quadrant, Mare Humboltianum straddles the limb, showing itself only at times of favorable libration. Humboltianum is a beautiful example of a multi-ring impact basin. Two of these mountainous rings are visible in my sketch, the 650 km ring just above lava floored Endymion at the bottom center, and the 300 km ring that encompasses the Mare. Chuck Wood pointed out in "Modern Moon" (Sky Publishing) that these rings would have hastened our recognition of the importance of basins if Humboltianum was placed more central on the visible face. Nectarian in age, it's formation occurred about 3.8 billion years ago, preceded by farside basin Moscoviense and followed by nearside Humorum. The mare fills only a partial area approximately 160 km wide of the inner 300 km ring. To the north, huge 204 km Belkovich has obliterated a large area of the basin floor, it's brightly glowing rim leads off to the left in my sketch. Long linear valleys, radial to the basin center in the zone between the two rings, are sobering reminders of the energy of the collision that creates large muti-ring impact basins. To the left, the outer ring seems to fail to continue the shape of the ring, presumably this is the result to some kind of post-impact modification.


Sketch details:

Subject: Mare Humboltianum Rukl: 7
Time: 12:41am - 2:34am PDT Date: May 10, 2009
Seeing: Antoniadi II-III Weather: clear, ocassional light breezes
Lunation: 15.18 days
Colongitude: 99.6 deg.
Illumination: 98.7%
Lib. in Lat.: +06 deg. 25 min.
Lib. in Long.: +03 deg. 42 min.
Phase: 347.0 deg.
Telescope: 12" Meade SCT f/10
Binoviewer: Denkmeier BV-25 with 2X nosepiece
45 deg. W.O. erect image diagonal
Eyepieces: 26mm Meade Super Plossls
Magnification: 234X
Sketch Medium: White and black Conte' on Black 400 Strathmore Artagain paper
Sketch size: 8" x 11"

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#2 frank5817

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Posted 11 May 2009 - 01:10 AM

Rich,

I did not realize how favorable the view was at the time of your sketch and observation. The eastern libration zone looks to be at its best. I have been trying to get a good look at crater Neper for a while. It has been cloudy here all weekend after sundown, so no lunar viewing for me.
That is one great sketch of Mare Humboltianum and its rings. :bow: :rainbow: :bow:
The last time I got a good look was the last time I saw craters Neper and Hubble. You really got around the corner there old eagle eye. :rainbow: The sketch and write-up are both wonderfully done. Are you far enough away from the marine cloud layer at your new place?

Frank :)

#3 kraterkid

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Posted 11 May 2009 - 10:43 AM

Thanks Frank! :D

"May Gray" and "June Gloom" are a thing of the past for me now that I've moved to the high desert. :jump:

#4 CarlosEH

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Posted 14 May 2009 - 01:04 PM

Rich,

An outstanding observation of Mare Humoltianum. An excellent example of a multi-ring basin on the Moon. Thank you for sharing it with us all.

Carlos

#5 kraterkid

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Posted 14 May 2009 - 01:56 PM

Thanks Carlos! :D

#6 revans

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Posted 14 May 2009 - 05:18 PM

Rich,

Impressive sketch ! Very 3D... almost like being there...

Rick

#7 kraterkid

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Posted 14 May 2009 - 11:07 PM

Thanks Rick! :D It was quite a thrill seeing it hugging the terminator like that.

#8 LivingNDixie

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Posted 15 May 2009 - 05:57 PM

Nice one Rick!

#9 kraterkid

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Posted 15 May 2009 - 09:06 PM

Thanks Preston! :thanx:

#10 rolandlinda3

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Posted 17 May 2009 - 05:09 PM

That's a downright pretty sketch, Rich. Hope you have less wind there then the west end of Antelope Valley. Winds stay pretty high hear...blowing-sand-on-optics speeds. Roland

#11 kraterkid

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Posted 17 May 2009 - 10:42 PM

Thanks Roland! :D It's pretty windy in Jacumba around springtime, but the locals say the winds abate in the summer. I think they must be right, I've had several days running where the winds have dropped down below 10 mph. Sand-on-optics speed! Oh my! :(






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