1 PRINT "From the June 1985 SKY & TELESCOPE, pp. 545-6."
2 PRINT
3 PRINT "This program calcuates, from three lines of known wavelength, the"
4 PRINT "wavelengths corresponding to any additional features.  The distances"
5 PRINT "of the lines of known wavelength are measured from some fiducial"
6 PRINT "point at the red end of the spectrum (so the values increase toward"
7 PRINT "the blue end) and should be well separated.
8 PRINT
9 PRINT "INPUT:  Measured distances (mm) and wavelengths (nm) of three lines"
10 PRINT "of known wavelength, measured distance (mm) of additional feature."
11 PRINT
12 PRINT "OUTPUT:  Calculated wavelength (nm) of additional feature."
13 PRINT
100 REM     WAVELENGTHS
110 REM
120 INPUT "FIRST KNOWN WAVELENGTH,  DISTANCE";W1,S1
130 INPUT "SECOND KNOWN WAVELENGTH, DISTANCE";W2,S2
140 INPUT "THIRD KNOWN WAVELENGTH,  DISTANCE";W3,S3
180 P=W2-W1: Q=W3-W1: R=S2-S1
190 S=S3-S1: T=S3-S2
200 A=R/P: B=S/Q
210 U=A-B: V=T/U: L=W1-V
220 D1=A*(W2-L): D2=D1+S1
230 C=(D1*T)/U
240 PRINT
250 INPUT "DISTANCE";D
260 IF D<0 THEN 310
270 W=L+(C/(D2-D))
280 W=INT(W+.5)
290 PRINT "WAVELENGTH = ";W
310 RUN "ASTRMENU.BAS"