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Jim Mosher
sage
Reged: 05/22/06
Posts: 233
Loc: Newport Beach, CA
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On Wednesday evening, observers in most of North America will have an opportunity to see the Moon under circumstances similar to those that, according to famed British-born American selenographer Ewen Whitaker, led to Galileo's famous first engraving of the waxing crescent Moon in his revolutionary book Sidereus Nuncius (published in March, 1610). Whitaker believes he can see details along the terminator which allow him to pinpoint the observations necessary to produce the engraving to the evening of November 30, 1609. Whitaker thinks Galileo based this engraving, and two other drawings, on observations he made on that date from Padua, Italy between sunset and moonset.
The modern dates and times on which the terminator will be sweeping over the same surface features as Galileo would have seen then fall between about 02:00 UT and 05:30 UT on April 10 (the evening of Wednesday April 9 2008 in North America). The match is particularly interesting this month because not only will the terminator be at the same longitude, but the twist angle (the Sun's latitude on the Moon) is quite close to what it was on November 30, 1609 (something that happens twice a year but is observable from only selected parts of the world).
This Wednesday, for observers positioned on a line running very roughly from Chicago through San Antonio, the moon will be setting at about 05:30 UT, so the entire sequence will be very similar to what Galileo would have witnessed if he had been observing on that night long ago. Those east of the line will miss the last part of the sequence. Those to the west will miss the first part, but see the Moon still up a bit in the sky at the equivalent of what Whitaker thinks was the end of Galileo's session (and actually the time Whitaker thinks corresponds most closely to the engraving) -- giving perhaps a better chance to photograph it.
Recently something that purports to be the original proof copy of Sidereus Nuncius has surfaced, with what are claimed to be Galileo's original drawings in the places where the engravings normally appear. Some believe this is real, others a forgery. The proponents of this being Galileo's original work have proposed a different timeline in which Galileo's crescent Moon engraving is said to have been made on December 31, 1609 – and based on views completely different (colongitude 338.4-341.1 with solar latitude = +0.2 deg) from what will be seen this month.
In view of this controversy, Whitaker is particularly keen to obtain photos showing what the passage of the terminator looks like this Wednesday (and on the next few evenings -- corresponding to dates on which he believes other drawings were made) -- especially images showing how the terminator appears with small aperture telescopes. Of course, many of you may already have in your archives images showing the terminator at the same position that Whitaker is interested in (colongitude 321.4-323.1 with solar latitude = +1.0 deg) taken in prior months or years.
More details and clearer predictions can be found here (and by following its links).
I'm passing along Ewen's request because he is not himself internet connected. Should there be any response, I'll try to let him know.
Those following the link will discover that there is particular interest in how the region around Janssen looks during these hours; but, given the vast uncertainties about what Galileo described and drew, they will also discover I'm personally skeptical that any new observations (short, possibly, of an accurate digital simulation of what the Moon looked like on every night from 1609-1610) will be able to resolve the controversy.
-- Jim
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Mare Nectaris
Pooh-Bah
Reged: 03/09/08
Posts: 1114
Loc: Toijala, Finland
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Hi Jim - and thanks for the interesting info - again.
Managed to spot a few minutes glimpse visually of the Moon here in Finland - by a mere coincidence - from a short window of sight among the clouds on the 9th of April 2008 at 20.20 UT (given by LTVT, Moons angular diameter was 1979,7 arc-seconds and 18,48 per cent of the Lunar disc was illuminated, attached is a LTVT map).
The disc was quite low slightly on the west side of the northwestern sky. It was colored like a piece of ancient juvel, tonally presenting a strong impression of copper, gently leaving a bit cold yet very beautiful overall impression.
My wife actually hinted this sight to me as she went to go to the balcony (for a smoke), and I am grateful to her, because I would have been sure that the skies are covered with clouds given the overall weather we had (again) yesterday.
We stared at the magnetic sight for maybe some 3 minutes - until it was gone again!
I told her that 398 years ago Galileo had probably studied a s o m e w h a t similar view.
I don't know exactly how close we got - I reckon we were about 6+ hours too early at the stage for having been able to spot the Galileo scenary by the naked eye, but - anyhow - the feeling was exceptional, and it was a magnificient moment to share - yet it was a short moment. But aren't the best moments in time almost always quite short!
Actually this was the second most beautiful Moon I have ever being able to spot. The most beautiful was on a summer night last year (on the 25th of June 2007 at 21.15 UT) when I was able to look at the Moon with a 6" reflector as it was very low on the southwestern skies (LTVT gives that the angular diameter of the Moon was 1777,6 arc-seconds and 79,62 per cent of the Lunar disc was illuminated back then).
The good old Moon then presented a sight like it were honeygold instead of cold copper - hanging very slow on the horizon, smooth and exteremely warm - yet not hot or pouring warm, but kinda cool - like it were liquid honeygold, just pouring out of the eyepiece.
Be well and clear skies!
Edited by Mare Nectaris (04/10/08 03:27 AM)
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Jim Mosher
sage
Reged: 05/22/06
Posts: 233
Loc: Newport Beach, CA
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Timo,
I'm glad you and your wife were able to enjoy such a splendid view of the Moon, however briefly.
I myself returned home to unexpectedly clear skies and was able to observe the Moon from 02:30 to 5:30 UT, which corresponded almost exactly to the terminator positions Galileo would have seen from sunset to moonset, should he have been looking on November 30, 1609.
In the text accompanying his crescent Moon engraving, Galileo describes a "dark gulf" which he says he observed for two hours, after which a "triangular peak" emerged from the darkness, then later still, three addition "points of light" surrounding the peak, and finally, just before moonset, the triangular peak merged with the bright part of the Moon, still surrounded by the three points. Whitaker interprets this as a description of the sun rising over the central part of Janssen (41°E/44°S) as seen through a small aperture telescope (Galileo was probably using an aperture of no more than 30 mm at a power to 20-30X).
The problem is that Galileo would have seen Janssen from a sun angle of +1.0 to +2.2°. I was just 15 minutes late in getting set up, but with the sun at +1.1° the central part of Janssen was already fully illuminated (as shown in the attachment). This was hardly surprising to me, since a previous photo I had posted on the internet, showing the region on March 4, 2006 at 02:31 UT, when the sun angle over Janssen was just 0.7°, already showed the peak in sunlight. At the scale of these pictures, I also couldn't see how stopping down the aperture to 1 inch did much of anything other than making the view dimmer. So if Galileo began his observations at sunset, when the sun angle over Janssen was +1.0°, it's very hard to see how he could have seen it as a vast featureless dark gulf for two hours.
This does not mean that Whitaker is wrong about Galileo looking at the Moon on November 30, 1609, or about his first engraving resulting in some way from that session; only from the verbal description of the events that were observed the strange triangular peak shown in that celebrated engraving could not be Janssen.
-- Jim
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Greyhoundman
sage
Reged: 11/20/07
Posts: 283
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Don't know if this is of use. But I noticed the "dots" near Janssen last night. This was taken at 9:04pm EDT.
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http://www.flickr.com/photos/greyhoundman/
http://greyhoundman.blogspot.com/
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Jim Mosher
sage
Reged: 05/22/06
Posts: 233
Loc: Newport Beach, CA
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Thanks! If I'm not mistaken 9:04 EDT is 01:04 UT, or about 1-1/2 hours earlier than the much poorer shot I posted (taken shortly after sunset here). The sun angle on the odd spoke-like pattern in the center of Janssen is +0.6° (vs. +1.1° in mine). Your photo represents quite closely what Galileo would have seen on Nov. 30, 1609 if he had been able to look at 14:20 UT -- about an hour and ten minutes before his local sunset.
I'm attaching a composite of earlier observations I made showing how the Janssen spoke pattern evolves with increasing sun angle. It looks like it first starts to appear out the darkness at a sun angle of slightly below 0°. For Galileo to have seen that on November 30, he would have had to have been looking at around 12:40 UT -- around his local noontime (which seems unlikely).
Perhaps someone can think of some other candidate for a triangular peak, surrounded by three points of light (as in the engraving), in a vast dark gulf of darkness in the southern cusp? It's quite possible it wasn't observed on November 30, 1609 -- Galileo never mentions the date of any of his Moon observations.
-- Jim
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Greyhoundman
sage
Reged: 11/20/07
Posts: 283
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Conversion to UT for my location would be -4 hours. That would put it at 5:04, on the 9th.
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http://www.flickr.com/photos/greyhoundman/
http://greyhoundman.blogspot.com/
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Jim Mosher
sage
Reged: 05/22/06
Posts: 233
Loc: Newport Beach, CA
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Thanks for the correction. My own photo was taken from Southern California at 7:30 pm PDT, which would have been 10:30 pm EDT, so at least the statement that mine is the equivalent of 1-1/2 hrs later than yours is correct. I live, incidentally, in a "UT-7" time zone (during daylight savings) and I normally add 7 hours to my local time get to UT, but I'll have to rethink that.
By the way, although 9:04 pm EDT was too early to correspond to the published engraving, it is very close to being the modern equivalent of the time Whitaker assigns to the first of a series of watercolor paintings he thinks Galileo made on that same night (Nov. 30, 1609). If you have the remainder of the terminator taken at around that time would you be so kind as to send it to me by e-mail: jimmosher@yahoo.com . No rush about it, but I could then put something together for Ewen showing the actual view observed by amateurs at that hour.
Thanks a lot,
Jim
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Jim Mosher
sage
Reged: 05/22/06
Posts: 233
Loc: Newport Beach, CA
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Thanks again to "Greyhoundman" for supplying the great photo of the crescent Moon taken from Moline, Ohio at 9:04 pm EDT on April 9.
His image is of particular interest because Whitaker says the pattern of features seen along the terminator in drawing "1" on this page of little watercolors bound with the manuscript copy of Galileo's book is distinctive enough to identify the drawing as having been made when the sun's colongitude (a measure of the position of the terminator relative to the surface features) was 321+/-2°, a condition that could have been observed from Padua, Italy on Nov. 30, 1609 at around 14:40 UT, or a little less than an hour before sunset.
Greyhoundman's image was photographed when the colongitude was 321.00°. The librations were a bit different than they would have been in 1609, but using the freeware LTVT software it's easy to mathematically warp Greyhoundman's image to the exact libration and phase that would have been seen by Galileo had he been looking at 14:38 UT (the moment in 1609 when this exact terminator position would have been observed). The result is shown in the attachment.
If Whitaker is right about the dating, this is, then, pretty much what Galileo must have been looking at as he created drawing "1". To me, the resemblance between the splashes of brightness shown along the terminator in the drawing, versus those in the photo, is slight, at best. But others may see it differently. Those more familiar with lunar sketching than I will undoubtedly have a better feel for whether the resemblance is good or not. And if the resemblance is not good, perhaps they will recall some phase during the lunar cycle when the pattern shown in drawing 1 does appear.
-- Jim
P.S.: had I followed the links, I wouldn't have had to ask for Greyhoundman's image by e-mail, because I would have realized that the full, unwarped original can be found on his Flickr page (and on his blog)
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frank5817
Post Laureate
Reged: 06/13/06
Posts: 3045
Loc: Illinois
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Jim,
I read this thread with great interest yesterday. I just happened to be sketching the moon at the same time as Greyhoundman took his photo. The photo is of course a more accurate capture but this is how the sketch of the region came out.
Frank 5817
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Jim Mosher
sage
Reged: 05/22/06
Posts: 233
Loc: Newport Beach, CA
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Great sketch (as usual), Frank!
It certainly seems consistent with what David (Greyhoundman) saw in and around Janssen at 9:04 EDT.
I'm curious if, as an experienced sketcher, you see anything in Galileo's drawing "1" that you would recognize as Janssen at this phase; or more generally, using David's photo as a guide, if you can relate any of the terminator splotches in that drawing to specific lunar features which would have been visible at the time?
I forgot to mention earlier that Ewen Whitaker's detailed interpretation of this, and the other drawings and engravings, can be found in a 1978 article, available here. In essence, he relies on identifying specific features along the terminator to determine the colongitude, and hence the date. But others feel Galileo's drawings (and especially his engravings) are more impressions of what the Moon looks like at different phases, rather than attempts to record fine details with accuracy. In that case, some of the dots, or exactly where they are placed, may be imaginary, making dating them in this way impossible.
-- Jim
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frank5817
Post Laureate
Reged: 06/13/06
Posts: 3045
Loc: Illinois
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Jim,
O.K. here is my guess, comparing David's photo to Galileo's "drawing 1". The bright and elongated mark (red) looks like it could be the western rims of Rosenberger, Rosenberger D and Hagecius collectively or the misplaced western rim of Boussingault E. The second (yellow arrow) could be the raised floor of Jannsen at the contact with Fabricius. Drawing with a blunt tool may account for the thick triangular mark. Finally the green arrow may be the western wall of Metius. I am really assuming that Galileo was trying for a reasonably accurate drawing.
Frank5817
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Jim Mosher
sage
Reged: 05/22/06
Posts: 233
Loc: Newport Beach, CA
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Frank -
Thanks for your expert analysis! That does seem a very plausible interpretation of the bright patches in that area. From the way Boussingault E appears in David's photo I'd guess that (if represented at all) it might be the final detached linear streak Galileo shows at the extreme left (far lunar south) in your labeled diagram. Trying to correlate the bright patches to the north with things observable at the same time as these features becomes much more problematic, at least for me. In his 1978 article, Whitaker points out for several of the "drawings" specific features visible along the terminator that led him to believe that they were made a particular colongitude. But this is not one of those.
These little "drawings", incidentally, are thought to be ink-wash sketches (made with a brush after outlining a guide circle in ink with a compass) and are frequently referred to as "watercolors". No one is quite sure if they were made at the eyepiece or created in the studio from other now-lost sketches. I also don't know if they had the beautiful sepia tones originally, or if that came from age (the whole manuscript has a similar brownish tone). But trying to accurately catch the bright patches as pieces of un-painted paper must have been tricky, especially at this small scale -- one slip of the brush and they're gone!
David told me privately he thinks he may see a hint of Gutenberg (the small keyhole-shaped crater prominent on the terminator in his photo) fairly well onto the sunlit part of the Moon in Galileo's drawing. Again, that seems plausible, but (as he points out) it would mean the terminator was about 4° more to the west than Whitaker assumed -- placing the colongitude at around 325°. That is certainly possible, but it would mean the drawing would have had to have been made on some other date, for by the time the terminator got to that position on Nov. 30, 1609 it would have been several hours past moonset in Padua. In this scenario the sunlit steaks in the south would then probably need to have quite different interpretations.
Too bad Galileo didn't put the dates on these drawings!
-- Jim
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photonovore
Moonatic
Reged: 12/24/04
Posts: 2472
Loc: tacoma wa
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Hi Jim,
I was observing the Moon last night (early this am actually) at the E2 position as listed on your website (thanks for that information!), using a 60mm terrestrial spotting scope using 20x and 30x. While doing so, it occurred to me that the odd disproportion of Galileo's drawing of that date (the huge crater on the terminator) could be the result of innate difficulties in assembling a proportional drawing of the entire moon when necessarily compiled from a series of the piecemeal eyepiece views he actually got. IOW, correctly transposing the proportions when one cannot see the entire Moon in one view, as was the case with Galileo, would add difficulty--and could easily result, i thought, in some object (like that crater) being portrayed much larger in the final composite drawing than it actually would have appeared-- if only he were able to view the entire moon in one field of view. Just a thought...
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Mardi
4" achromat, ETX-70.
Whitepeak Lunar Observatory Website
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