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[Centaur]

Well done again, Paulie. Thanks for continually monitoring the Moon.

As you likely know, Mare Orientale means Eastern Sea. Generally celestial items seen nearer an earthbound observer's eastern horizon are deemed eastern. Until astronautics began in the sixties, that side of the Moon was called eastern. Then NASA switched the designations of lunar east and west to conform to the perspective of an astronaut on the Moon. Nevertheless, the region you described is still called Mare Orientale. Wikipedia is wrong (as it often is) when it implies that originally the mare was misidentified as eastern due to telescopic inversion.

[patrickm]

Great report, Paulie. Your knowledge of the lunar surface is impressive and hard earned.

Are these photos from your Dob or from 16" at Conway?

[Paulie pchris00]

Feb 15, 2015 10:28:14 GMT -6 Centaur said:

Well done again, Paulie. Thanks for continually monitoring the Moon.

As you likely know, Mare Orientale means Eastern Sea. Generally celestial items seen nearer an earthbound observer's eastern horizon are deemed eastern. Until astronautics began in the sixties, that side of the Moon was called eastern. Then NASA switched the designations of lunar east and west to conform to the perspective of an astronaut on the Moon. Nevertheless, the region you described is still called Mare Orientale. Wikipedia is wrong (as it often is) when it implies that originally the mare was misidentified as eastern due to telescopic inversion.

I understand the need for the Apollo astronauts to have a familiar east-west orientation both in orbit, and on the lunar surface, but I like to observe the Moon in the more tradition sense of astronomy, as you point out, where direction is determined by celestial orientation. I usually refer to the limb that Mare Orientale straddles as the celestial eastern limb.

Feb 15, 2015 20:01:59 GMT -6 patrickm said:

Great report, Paulie. Your knowledge of the lunar surface is impressive and hard earned.

I'm not sure what was impressive. I knew about the libration from Sky & Telescope, although last month I discovered the libration on my own, and only used S&T to confirm my suspicion that this month there would be a similar libration at about the same time of lunation. Predicting it mathematically would have been impressive. I only happened to be looking at the right time last month, and was fortunate to be free at the right time this month. As for "hard won," I suppose perhaps, because I am crazy enough to get out my Dob no matter how cold it is if I have enough time. I wouldn't quite say that observing Mare Orientale was the same priority as the Venus Transit, but since I don't know when libration, phase, and weather will combine again favorably, I couldn't see passing up this opportunity, especially since I was already awake and out at that early hour. There was no good reason for me not to try last Friday morning. I have the appropriate wardrobe for staying warm in the bitter cold.

Feb 15, 2015 20:01:59 GMT -6 patrickm said:

Are these photos from your Dob or from 16" at Conway?

These were taken at home with my 6" Dob. I think most of the images on this thread were taken with my Dob.

[Paulie pchris00]

Earlier in this thread I have featured my favorite crater, Gassendi, and I have featured sunrise on the crater Ptolemaeus. On the night of January 30-31, I observed our Moon three times over six hours. During that time the terminator swept from the celestial eastern rim of Gassendi, to well past the crater. Early in the night, the central peak was just barely in sunlight, but by 1:30 AM, nearly the entire crater floor was illuminated.

I started the night observing in downtown Valparaiso, though in a spot where I wasn't likely to be bothered. I knew Gassendi would be somewhere near the terminator, but wasn't sure if it would be on the day or night side. I was happy to see that Gassendi was in mostly in sunlight. I spent about a half hour observing, and getting pictures.








Gassendi after 7:00 PM.


I had to work that night, or otherwise I would have went to Conway Observatory for the night. Valparaiso University was having an open house at their observatory, though, and it's close to where I work now, so when I finished my observing, I went to their open house. The night was a bit hazy, and not very steady seeing, but it wasn't bitterly cold, so at least two dozen people crowded into the little dome and control room down the hall. I let the visitors have most of the observing time, but when Dr. Hillwig had his students target our Moon, I was curious to have a look. I was excited to see Gassendi in the eyepiece at rather high power, and noticed that while the crater floor had been dark earlier, now there was sunlight falling across it. I said, "Oh! Gassendi!" For a moment Dr. Hillwig seemed embarrassed that he hadn't known what crater we were observing, then said, " Oh, it's Paulie. Now I don't feel so bad." At the end of the open house, I set up my Dob in the parking lot, and again imaged the Moon.







On my first break at work, I went out for my final observing session of the night, much shorter than either of the earlier sessions. After a quick look, I went about imaging, so I could wrap up and get back to work. By then, even the mountains to the celestial east of Gassendi, likely the remains of the rim of Mare Humorum, were rising into the sunlight. I finished the observation, pleased that over several hours I was able to watch my favorite crater during its morning.

[Paulie pchris00]

Very nice. Thanks for sharing, Eric.

[Paulie pchris00]

I found something interesting in some pictures already posted on this thread, and of course, they both feature Gassendi. Usually I notice libration by looking near the lunar limb, but this time I noticed the effect of libration by comparing photos of Gassendi. The dates were March 22, 2013, about 8:10 PM CDST, and January 31, 2015, about 1:20 CST. I looked up some information on Virtual Moon Atlas on both of those dates. (Btw, I'm losing confidence in VMA, based on some of my recent observations, but its data should at least be roughly correct). Here is what I found.

March 22, 2013- 8:10 PM CDST
Lunation: 11.01 days
Illumination: 78.4%
Libration in Latitude: +06°58'
Libration in Longitude: -04°10'


January 31, 2015- 1:20 AM CST
Lunation: 10.50 days
Illumination: 86.1%
Libration in Latitude: +06°46'
Libration in Longitude: +05°45'


The difference in latitudinal libration is only 12', but the difference in longitudinal libration is over 10 degrees. That's quite a difference, enough that I could tell just by comparing pictures. Gassendi appeared foreshortened east to west in the January 2015 images, whereas the March 2013 images, Gassendi appeared more round. Here are the images for comparison.



March 22, 2013, 8:11:20 CDST.



January 31, 2015, 01:20:09 CST.

[Centaur]

Feb 20, 2015 19:58:38 GMT -6 Paulie pchris00 said:

 (Btw, I'm losing confidence in VMA, based on some of my recent observations, but its data should at least be roughly correct). 

Interesting photos and observations, Paulie. Does VMA account for your location on Earth? Parallax considerations can be quite significant, leading to libration differences of as much as 1° compared with geocentric predictions.

[Paulie pchris00]

Feb 21, 2015 9:57:11 GMT -6 Centaur said:

Interesting photos and observations, Paulie. Does VMA account for your location on Earth? Parallax considerations can be quite significant, leading to libration differences of as much as 1° compared with geocentric predictions.

Virtual Moon Atlas can be configured for a given observing location. I don't remember where I got these coordinates, but the following is what the VMA data is based on: Observatory: 41°32'N +87°23'W.

It may not be exact, but it should be close enough for reasonable use anywhere near Chicago or NWI. The problem that I'm having is that for the observation of Gassendi on January 30-31, even at the last observation at 1:20 AM, VMA's graphics show the terminator falling through Gassendi crater, when even during the observation six hours earlier, the terminator was already beyond the crater rim. There have been other examples recently where VMA doesn't show the terminator where I observe it to be. If all of the numeric data in the ephemeris is correct, then it's not a big deal. I don't have the means to verify the other data from VMA, though, so I do question its accuracy.

[Paulie pchris00]

I may have made a meaningless lunar discovery on my break at work last night. "Astronomy" magazine did an article in July about rays on crater floors at sunrise and sunset. They listed a website to check for predictions. No predictions are listed for Schickard, yet I observed a ray. Scientifically useless, but at the moment, seems to be previously unreported.

www.lunar-occultations.com/rlo/rays/rays.htm

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