From: <Strebe(at)aol.com >
Date: Mon, 18 Apr 2005
Subject: [MapHist] Re: farnese globe

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Reading over my earlier post, I see that I wrote "he appropriately flairs the small circles", when, of course, I meant "flares".

As far as Mr. Duke's comments are concerned, I will note that I gave my estimates in percentages, not degrees, since I did not wish to confuse the latitude intended to be represented with its actual placement on the globe. Hence my estimate of 40% - 45% would correspond to 36 degrees - 40 degrees. However the point is moot, since Mr. Valerio's paper shows the ecliptic to be approximately where it belongs on the globe. (Thank you for the link to the paper, which I had not seen. http://www.coronelli.org/farnese/). While I attempted to compensate for unknown camera distance, unknown lens distortion, and unknown camera position, I failed; the cameras photographing the atlas were much closer to it than I guessed. The image at

http://sights.seindal.dk/img/orig/9456.jpg

affords a much more orthographic view than ones I found earlier, and shows tropics placed about as one would expect. I apologize for the confusion.

Given Mr. Valerio's measurements, I can confirm that the Folkes map reasonably faithfully renders the globe as a stereographic projection. I have posted an overlay to the image from Mr. Duke's site, based on Mr. Valerio's weighted mean measures. See

The red lines show how the corresponding "mean" lines from the atlas should project into the stereographic. Note that, working with an image of unknown pedigree -- unknown camera distance and lens characteristics -- not to mention slight instabilities in paper and variations on the globe itself, it's impossible to know how much of any mismatch is due to the respective authors' executions.

Regards,
daan Strebe


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