John, The difference in opinion between us arises from the other position we occupy. I use a sundial to help people learn. You use a sundial to make money with it. And both are honorable motives.
Willy Leenders Hasselt in Flanders (Belgium) Visit my website about the sundials in the province of Limburg (Flanders) with a section 'worth knowing about sundials' (mostly in Dutch): http://www.wijzerweb.be Op 13-feb-2011, om 19:47 heeft John Carmichael het volgende geschreven: > Hi Willy: > > Of course you are right that only a Solar Time dial can give Solar Time. > > But I must respectfully disagree with this comment: > The opinion of non-dialists should not affect us. > > Almost all of my customers are non-dialists. They are not astronomers. > (except for a few planetariums and schools). All my clients want to be able > to glance at their sundial and know what time it is. Most of them could care > less about Solar Time. We have a saying here: “The customer is always > right”. So I give them what they want. But I do ask them before I build > their sundials what kind of time they want. I also offer Daylight Saving > dials. In all my years of making sundials, I have never had a single > customer who requested a Solar Time dial. If I ever do get a client who > wants a Soilar Time dial I would give them what they want. I offer them, but > they NEVER want one! > > It is my job to give my customers what they want. I do however give them an > Owners Manual that explains Solar Time for those of them that are interested > in astronomy. > > Respectfully, > > John > > > From: Willy Leenders [mailto:willy.leend...@pandora.be] > Sent: Sunday, February 13, 2011 11:24 AM > To: John Carmichael > Cc: sundial@uni-koeln.de > Subject: Re: part 2 of longitude correction > > John, > > The main argument for an uncorrected time on a sundial, anywhere in the > world, is that the correction removes an information that only a sundial can > give, namely solar time. > How about an astronomer who corrects his device indicating sidereal time to > transform it in a clock time indicating device? > The opinion of non-dialists should not affect us. > It is our job to inform them about the difference between solar time and > clock time. > > Willy Leenders > Hasselt in Flanders (Belgium) > > Visit my website about the sundials in the province of Limburg (Flanders) > with a section 'worth knowing about sundials' (mostly in Dutch): > http://www.wijzerweb.be > > > > > > > > Op 13-feb-2011, om 18:28 heeft John Carmichael het volgende geschreven: > > > My friend, Jim Tallman and I have had many discussions about longitude > corrected dials. I know that many of the Western European dialists don’t > like longitude corrected dials- especially the British dialists. I can see > why they feel this way. Their three biggest arguments against longitude > corrected dials are these: 1) They aren’t traditional, 2) They aren’t > symmetrical, 3) They are so close to their Prime Meridian that the longitude > correction is quite small and almost insignificant. > > But there are equally good arguments for longitude corrected dials! > > In The United States, and many other places, the sundial may be located far > away from the Prime Meridian at the edge of a Time Zone. In a perfect World, > a Time Zone would only span 15 degrees. But most of our Time Zones have > wiggly irregular boundries that sometimes span distances far greater than 15 > degrees. Russia is an extreme example of this! There are parts of Russia > that are missing entire zones! Then there’s China. The entire country only > has one Time Zone! > > See: http://www.travel.com.hk/region/timezone.htm > > For places like these, a well-built traditional Solar Time sundial will give > a time reading that can be more than an hour off of Watch Time (Standard Mean > Time). A casual non-dialist would say that these sundials don’t work, > especially if there is no Equation of Time graph available with built-in > longitude correction! Correcting a dial for longitude solves this problem. > For this reason, I think longitude corrected dials are more user-friendly. > This is why Jim and I routinely make our dials with longitude correction. > > That’s my two cents worth. > > John Carmichael > > > > From: Jack Aubert [mailto:jaub...@cpcug.org] > Sent: Sunday, February 13, 2011 9:14 AM > To: 'John Carmichael'; 'Donald Christensen'; sundial@uni-koeln.de > Subject: RE: part 2 of longitude correction > > This has all been very instructive. I am not a complete beginner, but have > to confess that I was under the impression that rotating the dial plate with > respect to the fixed gnomon was sufficient. Somebody once told me I could do > this and I never really thought about it. If you actually think about the > longitude correction, it does become obvious that just rotating the dial > plate is not going to be right. > > For any dials I have made, I either used one of the programs like Shadows Pro > or Orologi Solari to include a longitude correction, or more frequently, > now, I use a delta cad macro and keep uncorrected solar time. I agree with > Willy Leenders that sundials should tell solar time. I have a watch that > can tell me mean time, but it has ceded to my celphone which is even better. > > > Thanks for the question and thanks for the good answers. I keep learning > things here, many of which I should already know but somehow missed. > > Jack > > > From: sundial-boun...@uni-koeln.de [mailto:sundial-boun...@uni-koeln.de] On > Behalf Of John Carmichael > Sent: Wednesday, February 09, 2011 6:46 PM > To: 'Donald Christensen'; sundial@uni-koeln.de > Subject: RE: part 2 of longitude correction
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