I may have jumped the gun with my last statement. While the orthographic projection clearly does not apply, several other azimuthal ones show promise, in particular the Airy, equidistant, and equal-area. Brad
On Wed, Jan 26, 2011 at 4:59 PM, Brad Lufkin <bradley.luf...@gmail.com>wrote: > I tried to send the following message with a 40K diagram attached but it > bounced, so I'm re-sending it without the diagram. I thought the limit was > 50K? > Brad > > On Wed, Jan 26, 2011 at 4:54 PM, Brad Lufkin <bradley.luf...@gmail.com>wrote: > >> Here's a diagram of an orthographic projection centered at Rio at the time >> in question. It's clear that this diagram does not match the flag of Brazil. >> While the north-south arm of Crux is indeed at the longitude of Rio, the arm >> itself can never be truly north-south, as the two stars have slightly >> different hour angles. Also, and far more importantly, Crux is too far north >> on the flag, being nearly at the same latitude as Rio (the center of the >> map). In fact, the declination of Crux is around -60 degrees, whereas Rio, >> as we know, is nearly on the Tropic of Capricorn. >> To find Crux in the diagram, look about two-thirds of the way down. It's >> the constellation containing Mimosa. >> I can't think of any projection, other than an artistic one, that would >> put the stars in these relative positions. >> Brad >> >> >> On Wed, Jan 26, 2011 at 2:11 PM, James E. Morrison < >> janus.astrol...@verizon.net> wrote: >> >>> Frank, >>> >>> It would take some effort to make a conclusive argument as to the >>> projection used on Brazil's flag, but the description on Widipedia says it >>> is an orthographic projection (the projection origin is at infinity). The >>> date and time when Crux (the Southern Cross) was on the meridian are correct >>> in the Widipedia article. I'll look at in more detail as time permits. >>> >>> Best regards, >>> >>> Jim >>> >>> James E. Morrison >>> janus.astrol...@verizon.net >>> Astrolabe web site at http://astrolabes.org >>> >>> Jan 26, 2011 05:21:44 AM, frank.k...@cl.cam.ac.uk wrote: >>> >>> Dear Roger (with a question for James Morrison), >>> >>> You prompt an interesting side-track in your >>> observation that... >>> >>> > The national flag for Brazil also incorporates >>> > an armillary sphere... >>> >>> It seems that you are living just a bit in the past >>> here. Aren't we all? The flag of Brazil incorporated >>> an armillary sphere until 1816 when it was largely >>> covered up and in 1826 it disappeared from the flag >>> altogether. See: >>> >>> http://en.wikipedia.org/wiki/Flag_of_Brazil >>> >>> This article describes the current flag in great >>> detail. It is dominated by a representation of >>> the night sky over Rio de Janeiro at 08:37 on >>> the morning of 15 November 1889. >>> >>> In an intriguing note, the article explains that >>> the positions of the stars were altered slightly >>> in 1992 to account for proper motion since 1889. >>> >>> The Brazilians are to be commended for their >>> insistence on precision but this alteration means >>> that the flag no longer represents the night sky >>> in November 1889. As such the current flag is >>> a bit of an iconoclast. >>> >>> I do hope that "Instruction on the Design of the >>> National Flag" is in the school curriculum in >>> Brazil. No wonder the country is doing well! >>> >>> The only detail that I would like explained is >>> just what projection is used. >>> >>> Can James Morrison comment please? >>> >>> Frank King >>> Cambridge, UK. >>> >>> --------------------------------------------------- >>> https://lists.uni-koeln.de/mailman/listinfo/sundial >>> >>> >>> --------------------------------------------------- >>> https://lists.uni-koeln.de/mailman/listinfo/sundial >>> >>> >>> >> >
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