--- On Thu, 11/11/10, Granny Arby <[email protected]> aka Roger Bailey wrote the following note but is was too big for the size filter. I have deleted the sketch to reduce the file size. I hope this gets through
From: Granny Arby <[email protected]> Subject: Re: "Digital" Analemmic sundial? To: [email protected], "Chris Dobbie" <[email protected]> Received: Thursday, November 11, 2010, 9:23 AM Hello Chris, Welcome to the world of sundials. The sundial mailing list is one way that we keep in touch and share ideas with others around the world. The other way is with national sundial societies, like the North American Sundial Society. As we are neighbours, Western Canadians sharing telus and our ISP, I will send you a personal note with further information on this topic. On first looking at your comcept, I see no reason that it would not work as you proposed. I have not seen this specific design but many of the ideas are built into other similar sundials. A rotating equatorial ring is commonly used to ajust for longitude and DST. An gnomon shaped like the analemma is also commonly used to correct for the EQT on equatorial sundials, The geometry of projecting the central gnomon onto the equatorial ring is equivalent to projecting a point on the ring to your disc in the centre. There are some sublties in calculating the exact shape of the analemma when projected flat. The elements of the design all seem correct. Well done! I am currently in Madeira, hiking for three weeks. Wow, what an island. Unfortunately there are few sundials here or in other parts of Portugal. But there are many armillary spheres, the mother of all sundials. A proper armillary sphere has rotating rings and uses the an ecliptic ring to show declination. After an earlier trip to Portugal, I studied armillary spheres and prepared a presentation on the topic for a NASS conference. It has also been well received at at RASC meetings in Calgary amd Victoria. It is available on my personal website www.walkingshadow.info as publication # 19 after clicking on Walking Shadow (sundials). You may find it interesting. The name analemmatic sundial is generally used to describe the sundial type with an eliptical hour ring and a movable, often human gnomon, Her the word has an extirely different meaning as there is no analemma shape on a correct analemmatic sundial. Your dial would be described as an equatorial dial with an analemma. Regards, Roger Bailey Walking Shadow Designs NASS Secretary As I am travelling, I cannot sent email using the normal email address. [email protected]. Granny Arby [email protected] is a backup. --- On Wed, 11/10/10, Chris Dobbie <[email protected]> wrote: From: Chris Dobbie <[email protected]> Subject: "Digital" Analemmic sundial? To: [email protected] Received: Wednesday, November 10, 2010, 12:28 PM Just in the last week I’ve become fascinated with sundials and decided to join this mailing list. This is my first post here and with that said I’d like to say hello to all members and ask that you forgive my noobish questions. I saw a “digital” equatorial sundial for the first time the other day and fell in love with its simple design, just a band of metal bolted to a rock. I soon realized that its simplicity came with a cost to functionality. I’ve since come up with a far less simple design that I think solves most functionality problems including equation of time and the inability of use between 6 pm and 6 am. You can’t really tell from the model but I envision the equatorial ring being able to rotate 360 degrees with markers along its track for longitude and DST correction as well as current times for other cities around the world. One could also make it universal by marking it in degrees and making the base adjustable. If build large scale, minute lines could be added to the analemma. I’ve only recently started researching sundials and the math of the analemma is still confusing me so I have a couple questions. I imagine if I calculated out the amalemma and checked the time at noon this dial would be fairly accurate but how accurate would it be at dawn and dusk? Would the angels of the analemme change? Also, would rotating the equatorial ring affect accuracy? If the dial does work and the amalemma and dial were marked in smaller increments, how accurate do you think it would be? Lastly, I’m wondering if you have ever seen this style of dial before in design or finished form? I have yet to come across one and would love to see any pictures or info that’s out there. Thank you so very much for any and all you can share with me. Cheers, Chris https://lists.uni-koeln.de/mailman/listinfo/sundial
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