Re: Transalpine hours

  -Original Message-From: John Davis <[EMAIL PROTECTED]>To: sundial@rrz.uni-koeln.de Date: 02 August 2000 08:54Subject: Transalpine hours Hi all,   I've come across a reference to "transalpine hours" in Heilbron's

Re: Wall calendar

-Original Message- From: Steve Lelievre <[EMAIL PROTECTED]> To: Sundial mailing list Date: 12 January 2001 16:39 Subject: Wall calendar You may be interested to know that in about 1970 one of the major UK banks (the Midland, I think) produced a wall calendar, a month to a page, in which

BSS Bulletin. Southern Hemisphere Sundial?

Well spotted!My guess would be horizontal, southern hemisphere.If vertical south-facing the Roman numerals would be upside down seen frombelow.John Lynes

Re: Ceiling Sundial

Here's an alternative approach, which would work best with two people: Set up a simple horizontal sundial, with declination lines, correctly oriented, beside the mirror, say a foot to one side. Using a laser pointer, or just a bare low-voltage filament lamp, cast a shadow of the gnomon onto the su

Re: Shadow casting program

Since nobody seems to have offered a reply to Albert's request for a program to show shadows cast by buildings, may I offer a simple suggestion? Use any perspective drawing program.  Arrange the viewpoint to be at a large distance from the building, and in a direction corresponding to the al

Ceiling Sundial

Here's a simpler proposal. Transfer the declination lines and hour lines of a horizontal sundial onto a transparent sheet. Mark a small circle on the centre of the mirror. Support the horizontal transparent sheet, rotated from north to south, with its nodus vertically above the centre of the c

Ceiling Sundial

In response to both Dave Bell and John Carmichael, I took the small mirror as fixed, and required it only to be flat and, of course, stable.  These are necessary conditions for any ceiling sundial.   My proposal does not require any knowledge of the actual alignment of the mirror.  John Carm

Re: Polar ceiling sundial

Anselmo Perez Serrada wrote -   "Maybe some of you didn't notice that if you lean the mirror towards the South so that it's slope equals half of your latitude then (a small hand-made wedge would do the job quite well) you get a polar sundial on the ceiling, with all its analemmas paralell to

Re: Polar ceiling sundial

Thanks, Fer. Apologies all round, and especially to Anselmo.  I now think his proposal would work after all.  But only in the winter months.  At noon at the equinox the reflected beam would be vertically above the mirror.  During the summer months the beam would be reflected south of the eas

Re: 17th c. Oxford

Harriet James will find a brief reference to the two Wadham sundials in Gunter's "Oxford Science" (volume 6 or volume 9, I think). Gunter mentions that one of the sundials is indicated in a plate by Loggan dated 1675. I doubt if this will be much help, but hope it may encourage somebody to do bett

Re: Seasonal Sunrise Marker

Extending Roger Bailey's treatment, if you know the time and direction of sunrise you can easily estimate the time and direction of sunset, or vice-versa: Time of sunset = 24 - (time of sunrise) Azimuths of sunrise and sunset are equidistant from the North-South meridian, remembering that sunrise

Re: Seasonal Sunrise Marker

Two words were carelessly omitted from the third paragraph of my last posting. Please accept my apologies. It's hard enough to digest even when the wording is correct! Below is a corrected version of the posting:- Extending Roger Bailey's treatment, if you know the time and direction of sunri

Re: Why the clock rotates clockwise?

It's often claimed that the fore-runners of mechanical clocks were physical models of the heavenly sphere(s). In the northern hemisphere this/these appeared to rotate clockwise. So clocks followed suit. John Lynes - Original Message - From: "Sumi Yoichi" <[EMAIL PROTECTED]> To: Sent: