I also have fond memories of the 1980 article in the Scientific American, Amateur Scientist column on the Slone analemmic dial. I was intrigued by the idea of analemmic hour lines so I keyed in the program and laboriously cranked out some results on a Timex Sinclair computer (the one chip wonder). It is now so easy to produce these results using programs like Fer de Vries "ZONWLAK" and Francois Blateyron's "Shadows" but the primitive programs did force you to learn. I never did understand Slone's cryptic equations or Jearl Walker's detailed descriptions but I am now comfortable with the usual math for calculating altitude, azimuth and projected shadows tracing declination lines and analemma.
This Scientific American article was one of the original hooks that caught my interest in sundials. In spite of the math being difficult, the program obsolete and incorrect, the article is excellent and I would like to share it. For those slightly interested, the original program from the article is reproduced below. For those more interested, I would be happy to send as an e-mail attachment a scanned copy of the original Scientific American article from the Amateur Scientist Dec 1980 and corrections including the addition of EQT and Dec subroutines suggested by Charles Kluepfel in the May 1981 edition. The six pages are in a set of four TIF format files totalling 522kb. Fax format (.awd) can also be supplied. If you want a copy, please reply by e-mail. I have been a subscriber to Scientific American for over 40 years and have a full set of all editions from 1971 to 1999 in my basement. I am happy to put the collection to use and quell the "Let's have a Garage Sale!" threats. Roger Bailey Walking Shadow Designs 51 N 115 W SLONE.BAS 10 CLS : RPD = 0.01745 : L= 35.0 * RPD : DL = 1.8 : H = 1.0 20 INPUT "DECLINATION (DEG0 ="; DECL : INPUT "DATE ="; A$ 30 INPUT "EQUATION OF TIME (MIN) ='; ET : ET = ET * 0.25 40 INPUT "IS DAIL FAST OR SLOW"; B$ ; D = DECL * RPD 50 IF B$ = "FAST" THEN ET = -ET 60 PRINT "DL ="; DL' "EQ TIME (HRS)', "TOTAL ANGLE ="; DL + ET 70 PRINT " ": PRINT "TIME (HRS)", "DIST (METERS)", A$ 80 X = TAN (L) : F = 1/ C0S )L) : G = X = 1/X : W = 1/ SIN (L) 90 FOR K = 0 TO 10 : C = K * 7.5 * RPD : B = TAN (C) 100 E = SQR ( (B * F) ^ 2 = G ^ 2) / G : J = 1/ (E * X) 110 A = ATN ( (G * E - J) / SQR (W ^ 2 - J ^ 2) ) 120 Z = TAN (A - D) / TAN (A) : DIST = H * (Z - 1) * (G * E - J) 130 PRINT T, DIST ; T = T + .5 : NEXT K : END At 07:54 AM 7/5/99 -0700, John Carmichael wrote: >Hello Peter: > >You are the first person who says they have seen a sundial similar to the >one I have proposed. I assume you mean the separation of the nodus off of >the style by placing it instead on the top of a vertical nodus located at >the dial center? Thank you for the Scientific American info, will look up >article next trip to library. As an accuracy check I'd like to compare the >printouts of several different programs. > >Thanks again, > >John C > >>On June 30th John Carmichael wrote: >>> >>>I know how to calculate and draw the declination lines for a vertical nodus >>>projecting onto a horizontal face. But nowhere can I find a formula for an >>>analemma projected onto a horizontal plane. >> >>John, >> Sorry for the delay in adding my thoughts to those you've already >>received, but I'm buried under piles of essays which must be marked... >> Scientific American published an article plus a programme in BASIC >>for such a sundial. The reference is the Amateur Scientist column for >>December, 1980 pp. 174-180. The dial described was made by C.K. Sloan. I >>have a pencilled note which adds that a correction was published in the >>May, 1981 issue. >> No doubt you may prefer to use ZONWVLAK, but if it would be of use, >>I think I once keyed in the programme (it's very short, conventional BASIC: >>a little cryptic...) and could try to find it if it would be of use. >> >> cheers, >> >> Peter >> >>---------------------------------------------------------------------- >>Peter Mayer | [EMAIL PROTECTED] >>Politics Department | >>University of Adelaide | 'phone:+61.8 8303 5606/5610 >>Adelaide, SA 5005 | FAX: (+61.8) 8303 3446 >>AUSTRALIA | >>---------------------------------------------------------------------- >> >> >> > >
