Dear John, Many thanks for the clarification...
> Oh but it does matter... Ah, I now understand... > The reason is that this dial needs to be corrected > for longitude shift (called Standard Time in ZW 2000). OK. All understood so far. > If I'm not mistaken, you are correct for those dials > that show solar time... Yes. Your assumption is right and here I declare a personal longitude-dependent problem... I live about 30 seconds of time to the east of the Greenwich Meridian and this has prejudiced me against standard-time dials. For example... Downing College has a new horizontal dial which shows Greenwich local time (the relevant Standard Time here) which sound fine. The snag is that the 12 noon line just looks like a mistake since it is offset from true north-south alignment by such a tiny angle. I would be happy with the dial indicating local solar time (the usual way) or Greenwich MEAN Time (which is well understood) but Greenwich local time is neither one thing or the other. If your dial is 77 degrees east and your Standard Time is for a longitude of 82.5 degrees, then my concern is much reduced. Your 12 noon line won't look like a mistake; its offset from vertical (or north-south) won't look like a near miss but something that is deliberate. You don't say whether this is a horizontal dial or vertical (or something different). I note this because wall dials are much less satisfactory in the tropics than closer to the poles. You will be OK until the Indians change their Standard Time or the local province decides to change it. This happened in Spain (or Portugal?) a few years ago and all the sundials suddenly went into error by an hour. Best wishes Frank --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
