Diese Nachricht wurde eingewickelt um DMARC-kompatibel zu sein. Die eigentliche Nachricht steht dadurch in einem Anhang.
This message was wrapped to be DMARC compliant. The actual message text is therefore in an attachment.
--- Begin Message ---I know analytic geometry is the base of any geometric software (though we might say that sintetic geometry was the historical base of analisys). What I have not understood is the mathematical level of the people to whom you want to explain the conic sections, i.e. the daily declination curves. Wouldn't it be easier to use some 3d free software like sketchup or geogebra?It is easy to draw in 3d the light cones and the corresponding opposite shadow cones. And their intersection with any wall or even complex surfaces. And, most important, everything is VISIBLE, even to those who are not good in maths.Moreover with geogebra 3d the thing is interactive (declination, latitude, inclination ...) and you can highlight the involved analitical equations.Francesco Ferro Milone Inviato da Yahoo Mail su Android Il mer, 20 nov, 2019 alle 12:00, sundial-requ...@uni-koeln.de<sundial-requ...@uni-koeln.de> ha scritto: Send sundial mailing list submissions to sundial@uni-koeln.de To subscribe or unsubscribe via the World Wide Web, visit https://lists.uni-koeln.de/mailman/listinfo/sundial or, via email, send a message with subject or body 'help' to sundial-requ...@uni-koeln.de You can reach the person managing the list at sundial-ow...@uni-koeln.de When replying, please edit your Subject line so it is more specific than "Re: Contents of sundial digest..." Today's Topics: 1. Re: Brief explanation/derivation for Horizontal-Dial's declination-lines? (Michael Ossipoff) 2. Re: Brief explanation/derivation for Horizontal-Dial's declination-lines? (Michael Ossipoff) 3. Re: Brief explanation/derivation for Horizontal-Dial's declination-lines? (Michael Ossipoff) ---------------------------------------------------------------------- Message: 1 Date: Tue, 19 Nov 2019 10:25:01 -0500 From: Michael Ossipoff <email9648...@gmail.com> To: Frank King <f...@cl.cam.ac.uk>, sundial list <sundial@uni-koeln.de> Subject: Re: Brief explanation/derivation for Horizontal-Dial's declination-lines? Message-ID: <caokdy5dmdgcjapsbgkgsqywcny1tbx7sy6twe7nnrokk5fr...@mail.gmail.com> Content-Type: text/plain; charset="utf-8" I've heard that dialists traditionally disregard atmospheric-refraction, when calculating sunrise an sunset times. That allows the use of spherical-trigonometry's tangent-formula, instead of the altitude-formula, a co-ordinate-transformation. But the orrery derivation of the altitude-formula seems just as easy as the derivation of spherical-trigonometry's tangent-formula. In fact, the orrery-derivations of the alt and az formulas seem, to me, easier. ...even though those formulas are larger than the tangent-formula. The tangent formula, being briefer, involves less arithmetic, but the orrery derivation of the alt and az formulas seem more naturally and easily explained. ------------------------ By the way, though I'd explain declination-line construction by the altitude-method, there might be advantage in calculating it by the trig-at-the-dial method. For one thing, the alt & az formulas can have subtraction, which can cause a loss of significant digits (which would only rarely matter, with today's many-digits machines). Also, if you want the measurement to be straightforward, instead of looking for the point on the hour line that's the right distance from the sub-nodus point, which isn't on the hour-lline, then you'd need to calculate the solar altitude and azimuth both. That, and the conversion to rectangular co-ordinates, and then a little work with those co-ordinates, probably amounts to a bit more arithmetic than the trig-at-the-dial method. 48 Tu Novembeer 19th 1524 UTC Michael Ossipoff -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://lists.uni-koeln.de/mailman/private/sundial/attachments/20191119/d671770e/attachment-0001.html> ------------------------------ Message: 2 Date: Tue, 19 Nov 2019 10:34:43 -0500 From: Michael Ossipoff <email9648...@gmail.com> To: Frank King <f...@cl.cam.ac.uk>, sundial list <sundial@uni-koeln.de> Subject: Re: Brief explanation/derivation for Horizontal-Dial's declination-lines? Message-ID: <CAOKDY5AF1zPTa5RZ-mqQJLH0A4fha4abCoq5duRZ=xk6dz3...@mail.gmail.com> Content-Type: text/plain; charset="utf-8" I should mention that, when posting about the trig-at-the-dial method, I assumed a positive declination. When the declination is negative, you just use NEO instead of its supplement. 48 Tu November 19th 1534 UTC -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://lists.uni-koeln.de/mailman/private/sundial/attachments/20191119/82e8ed86/attachment-0001.html> ------------------------------ Message: 3 Date: Tue, 19 Nov 2019 16:03:33 -0500 From: Michael Ossipoff <email9648...@gmail.com> To: Frank King <f...@cl.cam.ac.uk>, sundial list <sundial@uni-koeln.de> Subject: Re: Brief explanation/derivation for Horizontal-Dial's declination-lines? Message-ID: <caokdy5cxtzogj0uftnpsijpucm7bpuqp6ikbaby9ajjti3o...@mail.gmail.com> Content-Type: text/plain; charset="utf-8" I said it backwards. For positive declination, use NEO. For negative declination, use 180 - NEO. 48 Tu November 19th 2103 Michael Ossipoff -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://lists.uni-koeln.de/mailman/private/sundial/attachments/20191119/ca9bb570/attachment-0001.html> ------------------------------ Subject: Digest Footer _______________________________________________ sundial mailing list sundial@uni-koeln.de https://lists.uni-koeln.de/mailman/listinfo/sundial ------------------------------ End of sundial Digest, Vol 167, Issue 7 ***************************************
--- End Message ---
--------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
