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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: formula for refraction
From: Dave Walden
Date: 2007 May 01, 20:33 -0700
From: Dave Walden
Date: 2007 May 01, 20:33 -0700
The following short FORTRAN program reproduces the critical table for refraction from the NA. It is NOT based on fitted equations. It uses the canonical multilayer-ray-following method of Biot-Auber-Standish (Astronomical Journal,119,2472-2474,2000 May). It calls the slREFRO program of Wallace based on the work of Hohenkerk (HMNAO. Sept 1984). http://stsdas.stsci.edu/cgi-bin/gethelp.cgi?refro.hlp You can change pressue, temp, humidity, etc to generate your own table. program dwrefracna implicit none real*8 ZOBS,HM,TDK,PMB,RH,WL,PHI,TLR,EPS,REF real*8 pi,xi,rlim print*,'from dwrefracna.f' pi=4.d0*datan(1.d0) print*,pi hm=0.d0 phi=45.d0*pi/180.d0 c na 2007 values tdk=273.15d0+10.d0 pmb=1010.d0 rh=0.80d0 wl=0.50169d0 c assume tlr .0065 tlr=0.0065d0 eps=1d-10 rlim=+5.35d0 do 4 xi=9.d0,90.d0,1.d0/60.d0 zobs=pi/180.d0*(90.d0-xi) call slRFRO(ZOBS,HM,TDK,PMB,RH,WL,PHI,TLR,EPS,REF) ref=ref*180.d0/pi*60.d0 if(ref.lt.rlim)then print'(i3,f4.0,f8.5)',int(xi-1.d0/60.d0) & ,60.d0*(xi-1.d0/60.d0-int(xi-1.d0/60.d0)) print'(8x,a1,f3.1)','-',rlim rlim=rlim-.1d0 endif 4 continue end from dwrefracna.f 3.14159265 9 55. -5.3 10 7. -5.2 10 20. -5.2 10 32. -5.1 10 46. -5.0 10 59. -4.9 11 14. -4.8 11 29. -4.7 11 44. -4.6 12 0. -4.5 12 17. -4.4 12 35. -4.3 12 53. -4.2 13 12. -4.1 13 32. -4.0 13 53. -3.9 14 16. -3.8 14 39. -3.7 15 3. -3.6 15 29. -3.5 etc. --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---