Hello guys. I was trying to determine the geographic location of the observer by measuring the elevation of two distinct stars at a certain time. Well, I am not very skilled in programming and I found this script for Octave and tried to use it. My data: Star A: Arcturus(α Boo) Right ascension: 14h 15 m 39.7s Declination: +19° 10' 56" Time: 19:31:11 UT Elevation: (100-89.9)*0.9= 9.09° Elevation after the refraction correction: 9.0° JD1 = 2455097.31332 Star B: Mirfak (α Per) Right ascension: 03h 24m 19.4s Declination: +49° 51′ 40″ Time: 20:05:29 UT Elevation: (100-61.5)*0.9= 34.65° Elevation after the refraction correction: 34.62° JD2= 2455097.33714 script: # 1 rad rad=180/pi # 90degrees-elevation r1 = 81 r2 = 55.38 # coordinates of the first star # Arcturus, a1 = a1 - ts a1 = 213.92 - 15*(19+(38/60)+(20.2/3600)) d1 = 19.18 # coordinates of the second star # Mirfak a2 = 51.081 - 15*(20+(12/60)+(43.9/3600)) d2 = 49.86 # their distance rad*acos(sin(d1/rad)*sin(d2/rad) + cos(d1/rad)*cos(d2/rad)*cos((a2-a1)/rad)) # first estimate of the geographical location a = 16 d = 50 for i = 1:3 t1=sin(d1/rad)*sin(d/rad)+cos(d1/rad)\ *cos(d/rad)*cos((a-a1)/rad) t2=sin(d2/rad)*sin(d/rad)+cos(d2/rad)\ *cos(d/rad)*cos((a-a2)/rad) p = [ rad*acos(t1) - r1, rad*acos(t2) - r2] sqrt(p(1)**2+p(2)**2) # susbstitution u = -1/sqrt(1 - t1**2) v = -1/sqrt(1 - t2**2) # derivation matrix m = [ -u*sin((a-a1)/rad)*cos(d1/rad)*cos(d/rad),\ u*(sin(d1/rad)*cos(d/rad) - \ cos(d1/rad)*sin(d/rad)*cos((a-a1)/rad));\ -v*sin((a-a2)/rad)*cos(d2/rad)*cos(d/rad),\ v*(sin(d2/rad)*cos(d/rad) - \ cos(d2/rad)*sin(d/rad)*cos((a-a2)/rad))] # inverse matrix [im,c] = inv(m) # linear equations x = -(im*p) # and addition to the initial estimates a = a + x(1) d = d + x(2) endfor ts is apparently the sidereal time a and r1, r2 are 90 degrees minus elevation The observer should be around 16.6 degrees east and 49.2 degrees north but I am getting very imprecise values. Even some parts of the script do not seem to e doing anything. Is there some error there or maybe is there a more elegant way to do the computation? Thanks for any help.