Maybe Letronne on the waning moon terminator

August 20 2006 03:30 UT – 05:35 UT
Location: Bray Co Wicklow Ireland 53.2000ºN, 6.1000º W
Sky - Watcher 200mm
Eye Piece 8mm TVP
Pencils Steadtler Softlead 6B & B
Rite in the Rain Sketch Pad
Humidity 87%
Wind Calm
Temp 19 degrees
Seeing 2

I decided to get up and checkout the waning crescent moon. I also hoped to see the alignment of this thin morning moon with Venus, Saturn and Mercury just prior to sunrise. Probably a bit too hopeful, as Saturn and Mercury were so close to each other and the sun.

I stick a load of pencils in my pocket to grab what I could from the cloudy Irish early morning sky it’s a little cold but when I spot the moon, I decide to go for a sketch, despite the looming thin cloud.

Of course the finder scope is out of alignment so I nudge the scope toward the light and there she was looking really good. What to draw? Always a question that has too many answers, answers like everything

The large crater Schickard was looking very oblique to the south away from the terminator and Herodotus, Aristarchus, and Vallis Shroter were prominent way below in the north.

I settled to a crater/feature just around the mid line of the terminator because it had a string of highlighted areas receding from it into the blackness of the moons night. Of course I did not check what it was before I started to sketch, I mean there was fast cloud threatening to take it away from me at any moment. I was up and I was going to have something for the effort. I had some coffee milk and had look with my 8mm TVP eyepiece. I started to sketch and of course thin cloud was a problem. I aligned my scope in - between clouds using my red light on a deck chair about 25 feet away.

My telescope was really wet but my new damp proof paper is so so good. 03:51UT I did not think the sketch was on but then, I locked on the moon again at 04:14 UT.

Oops!! I am standing in the chrysanthemums. It’s so much brighter now so I did the sketch in between clouds until it was too bright to see any proper detail on the lunar surface.

05:15 UT I head down my street to check out the planets, but alas a massive cloud bank obscures them and the sun is rising somewhere behind the greyness.
05:35UT the suns bright rays spike through the cloud bank and turn the sea an apricot hue. Large orange and peach coloured clouds mingle with lovely blue noctilucent streaks and in minutes the whole sky is akin to a Turner painting.

The morning after the night before its not so easy to identify my crater/feature. Waning moon terminators make very contrasting shadows and areas look quite different as the suns light is falling in away that can be very confusing. I do love the contrast and shapes along the terminator, after days of rain it was nice to look at moon again. Next time ID target before getting stuck into drawing.

So no planets, they got swallowed up by the marine cloud bank, and the advancing daylight.

I ended up with a lost lunar feature but a beautiful pastel sunrise.
So if you were observing the moon on the same evening, same time, did you see this feature?. I think it is possibly Letronne a Walled Plain in the South-West part of Oceanus Procellarum. Not one of my better sketches but I still would like a positive ID.

Deirdre Kelleghan
Irish Astronomical Society
www.irishastrosoc.org

At least it was clear for you, I had hoped to see the conjunction also, but 100% cloudy here :roll:

Keith..

Deirdre,I was trying to reconcile Letronne in my Rukl atlas with your sketch and I came up with a complete blank.

Give a dog a bone.

I printed out the sketch,rotated it just over 90 degrees anticlockwise (North up.Sun on left) and searched around that area of the moon (on the atlas!)

Letronne is centred 11 deg.S 42W.

Just 10 deg. south of this there is the crater Mersenius at 21 deg.S 49W.

The three craters Mersenius, Liebig and one called "D" (to the Lunar west of Mare Humorum) bear several points of resemblance to your sketch.

Mersenius is the big one,Liebig just south of it and D on the edge of the Mare Humorum.

The more I look at your sketch the more it looks like the Rukl trio.

What do you think ?

Peter.

Well Peter, thanks a lot for even trying to help sort out my moon mess.I had given up on this one myself. I know its a not so good drawing with fewer points to compare than my other efforts.

I looked at the area on VMA and traced and slightly nudged my sketch into place and Liebig,Mersenius, Mersenius D and Mersenius P lie in the right places,just about.

Only problem is the black areas in my sketch is the terminator and on VMA the terminator is a bit to the left and that area in my sketch is lit.

So not out of the woods yet here, unless the VMA terminator is not very realistic or there is something wrong with my settings.

South is up in my sketch and on my VMA. I think whenever the moon shows itself again :shock: I will check it out and make a better sketch to nail it down.

Deirdre Kelleghan
Irish Astronomical Society
www.irishastrosoc.org

I think thats it all right Deirdre.
It's not spot on, but it's hard making an accurate rendering in the dark.
You are too hard on yourself !
Peter.

Deirdre,

Peter's suggestion about Mersenius is an excellent one, but your original suspicion that you had drawn Letronne may still be correct.



The above image, which I have attempted to upload to the files area, compares your lovely sketch to an Apollo 16 photo of Letronne (with opposite lighting) taken from the Wikipedia article at:

" en.wikipedia.org/wiki/Letronne_(crater) "

The prominent isolated crater at the bottom of the Apollo photo, if I am not mistaken, is Flamsteed A, which might be represented by the the dark spot in your drawing. According to VMA the terminator would have passed through the center of Flamsteed A at around 4 UT on 20 Aug 2006, consistent with your depiction. Also the bright promontory you show to the left of the semi-circular basin very strongly resembles the promontory shown in the Apollo photo. I am unsure whether that particular promontory should be so readily visible at this sun angle, but it seems possible. Perhaps someone has a photo of this region taken under similar lighting conditions.

-- Jim Mosher (jimmosher@yahoo.com)