NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: formula for refraction
From: Bill B
Date: 2007 Mar 22, 20:08 -0400
From: Bill B
Date: 2007 Mar 22, 20:08 -0400
Frank > Yes, it turns out that the VLOOKUP function in Excel has a slightly > different definition from the one in the spreadsheet I was using. Just > change the third argument in each VLOOKUP from "1" to "2". Then it > works. You're good. You not only answered my questioned but anticipated my next question. At this point I have the following: =VLOOKUP(INT(B2),G10:H100,2)*(1-(B2-INT(B2)))+VLOOKUP(INT(B2)+2,G10:H100,2)* (B2-INT(B2)) It seems to be working a lot better, but Excel (or me) still seems to have problems. B2 C2 40.0 1.132 (matches column H) 40.1 1.124 40.2 1.117 40.3 1.109 40.5 1.094 40.6 1.086 40.7 1.078 40.8 1.071 40.9 1.063 40.99 1.056 41.0 1.093 (matches column H) Mean of 40.0 and 41.0 1.113 There seems to something wrong. Note: "INT" in my Excel rounds down the nearest integer. As a follow up, what is your opinion of the Saemundssen quoted in Meeus for Hc to H (below) as opposed to 57"/tanH R = 1.02 / tan ( H + 10.3/ (H + 5.11)) where H is the CALCULATED altitude. Thanks again Bill --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---
