Thank you Brad! I only looked at the explaination, not at the formula itself. Sorry. Problem solved. Have a great day! Thomas
2010/3/16 Brad Lufkin <[email protected]>: > the term "a" in your formula is the Sun's apparent altitude in degrees (see > Chapter 16 of Meuus's Astronomical Algorithms). > > On Tue, Mar 16, 2010 at 12:27 PM, Thomas Steiner <[email protected]> > wrote: >> >> Hi all, >> I am looking for a formula for refraction. >> At http://www.sundialsoc.org.uk/glossary/equations/equations.htm ist says: >> >> 10. Sun’s refraction >> Ro=1/ (tan(a+7.31/(a+4.4))) >> Ro is the refraction in arcmins for a temperature of 10ºC and an >> atmospheric pressure of 1010 mb. For other conditions, a multiplying >> factor of 0.28P/T is required, where P is the pressure in mb and T is >> the temperature in kelvins ( = temp in ºC + 273). >> >> but obviously refraction does also change with the sun's altitude. >> Only for low altitudes there will be refraction. Do you have a simple >> formula or source for this by hand? >> Danke, >> Thomas >> >> --------------------------------------------------- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> > > --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
