From: Roger Bailey Sent: Sunday, May 28, 2017 9:32 PM To: Nathaniel Shippen ; [email protected] Subject: Re: East/West Vertical Bifilar Sundial Hello Nathaniel, Yes, it is quite doable. Here is a sketch produced with Fer De Vries Zon 2000 for a bifilar in Honolulu Hawaii, lat 21.3° long 158°, X thread 25, Y thread 15, dec 85° east of south, Inc 88°. The sketch was too big for the SML size filter. This is the note without the sketch, available on request. The red lines show the threads, the black lines are the hour and declination lines. Doable? yes. Understandable? no. To understand read the NASS Compendium. Here over the last 20 years there are over 60 documents related to bifilar sundials: articles, programs, presentations by the giants in the field, Fred Sawyer, Rafael Soler Gaya, Dominique Collin, Gianni Ferrari and Fer de Vries. Rafael Soler Gaya has designed and commissioned some excellent bifilars based on catenary curves and conic sections in Mallorca. See my presentation on Sundials in Mallorca here. https://drive.google.com/open?id=0B14iMmxzLvJWRkpnSk1jbE5odTg Fred Sawyer has published on the origins of bifilar sundial starting in 1978. Fer De Vries program is easy to use to show what the lines look like. Alll this information is available to all NASS members. see www.sundials.org Regards, Roger Bailey Walking Shadow Designs Sent: Sunday, May 28, 2017 1:35 PM To: [email protected] Subject: East/West Vertical Bifilar Sundial I've seen some info on bifilar sundials, and they look very interesting. I thought I would try to make a simple one (if that is possible). An east and/or west facing vertical dial would be the most useful at my location. Actually the surfaces I would be using decline a little south of west and north of east (and also recline slightly). I would be sketching in the time marks (Hawaii Standard) empirically since I am also some 8 degrees west of the standard meridian. Is this doable? Are the computations for the threads and the point of origin for the hour lines fairly simple? If yes I'll dig in and do the necessary research, just don't want to be off on an impossible quest. Thank you in advance for your help! Nathaniel Shippen -------------------------------------------------------------------------------- This email has been checked for viruses by AVG antivirus software. www.avg.com -------------------------------------------------------------------------------- --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
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