************************************************************************************************* From: Dave Mitsky Subject: Walther Sunset Ray Message: Rob,
I just thought that I'd bring you to speed on the whole Walther/Walter thing in case you haven't heard. It seems that there's been some confusion about the true name of the crater Walther. Old lunar atlases, including the original Kalmbach Press Atlas of the Moon by Antonin Rukl, used the name Walter, which apparently was changed to Walther by the IAU in 1979. I was using the old Rukl atlas when I discovered the "Walter" Ray and the name on chart 65 was, of course, Walter.
http://en.wikipedia.org/wiki/Walther_(crater)
In summation, the name of the ray should be changed to the Walther Ray.
I'd like to add an amendment to my report at http://www.lunar-occultations.com/rlo/rays/walter.htm mentioning the fact that at the time that I discovered the ray this information was not widely known and I was going by what the Rukl atlas called the crater.
The Walter Lunar Ray, was detected by Dave Mitsky, and reported on the sci.astro.amateur
newgroup on 5/29/97. The report is as follows:
By comparing certain parameters in the ephemeris, and what the predictions showed, we know that
the colongitude at the time of the observation was 179.54d (178.595d avg), and that the desired
solar altitude over the crater was .591 degrees setting.
A New Lunar Ray? 5/29/97
Date: 1997/5/29
Location: ASH Naylor Observatory, Lewisberry, Pa.
76d53'4" west, 40d8'54" north; elevation 570 feet
Seeing: good
Transparency: good
Dome Temperature: 52 d F at session's end
Instrument: 17" f/15 classical Cassegrain
Ocular: 26mm Tele Vue Ploessl (249x)
Time: 07:10 UT
After I finished up a successful Herschel 400 globular cluster hunt on Thursday
morning (I bagged 9 new H400 objects) I took a quick look at Jupiter and then
the rising Moon as it obliterated the summer Milky Way. Although it was getting
very late and quite chilly I was very happy to chance upon what just might be a
new "lunar ray". I was scanning along the terminator at 249x when I noticed a
triangular ray of sunlight streaming through a break in the western crater wall
of Walter (at approximately 2 degrees west, 33 degrees south - Rukl chart 65).
The ray illuminated Walter's western floor and the lower part of its central
peak (the upper part was in direct sunlight, I believe). At approximately 07:42
UT I spotted a "reverse" triangular shadow being cast from an object on the
western wall onto the illuminated crater floor. I could not stay any longer and
by the time I had returned to my residence and set up my C4.5 (about 08:30 UT)
the phenomenon was over and the crater floor was in darkness.
Dave Mitsky
Harrisburg, PA
ASH, DVAA
Taking the known data, that the event was observed on 29 may 1997, I used harry jamieson's
"Lunar Observer's Toolkit" to get specifics on the ephemeris of the moon at that time. Since
the program only has inputs for longitude and latitude in degrees and minutes, I rounded the
site information to: 75d 53m longitude, and 40d 09m latitude, and the altitude to 173 meters.
The ephemeris for that instant was:
Since the emphemeris did not have a "desired solar altitude", but did have the option for
reproducing the lighting conditions, I used his date and time to generate the first
predictions. They were:
starting date = 1997 / 1 / 1 u.t.
site longitude = 75.88 latitude = 40.15 elevation = 173 meters
feature = walter
longitude = 0ø42' latitude = -33ø 0'
reproducing lighting for: 1997 / 5 / 29 at 7 : 10 ut
desired solar altitude = 0.591ø (setting), azimuth = 268.647ø
average co-longitude = 178.595
in the time column, d=daylight, t=twilight
---- moon's ----
topocentric -- earth's -- ------- sun's -------
ut date time altø semi-diam" Longø Latø Colongø Latø Azimø
1997/ 1/ 1 9:25 45.86 910.48 -5.32 -0.05 177.59 1.54 272.22
1997/ 5/29 7:10 17.22 977.63 -0.02 -2.03 179.54 -1.46 268.65
1997/ 8/25 15: 7D 36.00 942.16 7.45 6.71 178.88 -0.44 269.86
1997/10/23 13:56D 48.11 912.40 6.32 4.71 177.89 1.08 271.67