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Messier and Messier A : Skipping rocks on the Moon

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#1 kraterkid


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Posted 09 June 2009 - 11:24 PM

One billion years ago, give or take a couple of hundred thousand years, a small asteroid, perhaps only a few hundred meters wide, hurtled in, low over the eastern lunar limb, impacting into the basalt plains of Mare Fecunditatis. The very slight angle of incidence into the mare resulted in an excavation of the elliptically shaped 9 by 11 km Messier crater in an explosion of ejecta, shooting laterally to the north and south sides of the crater as well as down range to the west. This butterfly pattern of rays are common in low angled impacts. In addition, the forward moving ejecta falls ahead in the direction of the impactor, creating forward facing rays. From Messier this down range ejecta appears to have impacted into the western rim of an pre-existing crater, In just a a few milliseconds it’s once relatively round rim was modified into the egg shaped, 13 x 11 km Messier A. Two rays developed as the ejecta was deflected off the rim, continuing for over 100 km and vanishing somewhere near Lubbock and Leaky.

Sketch Details:

Subject: Messier and Messier A (formerly W.H. Pickering) Rukl: 48
Date: 5-30-09 Time: 4:55 to 5:40 UT
Seeing: Antoniadi II-III Weather: clear
Lunation: 4.66 days
Colongitude: 330.2 deg.
Illumination: 28.3%
Lib. in Lat.: +01 deg. 44 min.
Lib. in Long.: +03 deg. 32 min.
Phase: 115.7 deg.
Telescope: 12" Meade SCT f/10
Binoviewer: Denkmeier BV-25 with 2X nosepiece
45 deg. W.O. erect image diagonal
Eyepieces: Pentax XW 20mm
Magnification: 305X
Medium:Sketch White and black Conte' on Black 400 Strathmore Artagain paper
Sketch size: 9" x 12"

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#2 mapofthedead


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Posted 10 June 2009 - 09:05 AM

I refuse to believe this is a sketch and not a photograph - absolutely phenomenal Rich!

#3 Sarkikos



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Posted 10 June 2009 - 10:22 AM


Nice job! Makes me want to look for Messier and Messier A next time I observe the Moon. I use a binoviewer, too. Great for lunar work. But Luna must be pretty bright through a 12". Do you use a filter? Which one? I've tried several, but so far I like the #47 Violet best. Not a true natural color view, of course, very easy on the eyes at 3% VLT.


#4 kraterkid


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Posted 10 June 2009 - 12:33 PM

Thank you James and Mike! :D

Mike, I use no filters when observing the Moon (maybe that's why my old eyes are fading! ) Although at powers less than 150X the light is intense, I usually sketch at around 250X or greater which helps to diminish the intensity greatly. This one was done at 305X. I'll look into that #47 Violet filter though, because I sometimes sketch at 80X-150X for those wider synoptic views.

#5 dgs©



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Posted 10 June 2009 - 12:55 PM

I'll have to add those to my list of things to look for.

Was the sketch made over one observing session or multiples?

I ask, thinking that the ejecta rays look like something that would show up better under high illumination, yet the craters are in deep shadow. :shrug:

The sketch does look nearly photographic, but I've seen plenty of Rich's work. :grin:

#6 kraterkid


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Posted 10 June 2009 - 01:24 PM

Thanks David! :D

The sketch was made in one observing session, although the lighting was moderately high at this colongitude.

#7 Jeff Young

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Posted 12 June 2009 - 05:34 AM

Wow, Rich, great depth of color there.

Or would that be depth of gray? In any case, it has a wonderful richness to it (no pun intended).

-- Jeff.

#8 kraterkid


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Posted 12 June 2009 - 10:51 AM

Thanks Jeff! :D I think I remember someone saying (maybe it was Ansel Adams) that black and white is more colorful than colors. It seems that when I'm limited to a gray palette, I concentrate very hard on the subtle variations in albedo.

#9 LivingNDixie


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Posted 12 June 2009 - 11:53 AM

Very nice! I caught Messier and Messier A once when the Sun angle was low, and seeing the shadow from the rim go across the lunar plains for miles was very impressive.

#10 kraterkid


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Posted 12 June 2009 - 01:57 PM

Hey Preston! :D Thanks!

I'm hoping for sketches at lower sun angles. That must have been an awesome sight, so close to the terminator. I was surprised to learn that the rays are visible even at these colongitudes. I'm guessing that it is an indicator of crater youth.

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