Arthur,
I think in the last part of your message you might be asking when
does the effect, if considered at all, become inconsequential? Perhaps the
attached graph may provide some information, the equation used came from
Meeus, Astronomical Algorithms (15.4). I hope the file size, 8k, doesn't
prove to be a pain for anyone, I'm assuming it won't be but please feel
free to flame and rave if it is.
I would guess that on whole the variation in atmospheric
conditions would make it a rather difficult measurement to make and at the
very least one involving a number of variables.
Luke
Arthur Carlson wrote:
> Atmospheric refraction deflects the rays of the sun about 1/2 deg near
> sunrise and sunset, which should result in about a 1-1/2 min error in
> the reading of a sundial. Is this effect easily observed? At what
> height above the horizon does this effect start to become noticeable?
>
> Art Carlson
Attachment converted: MAC Hard Disk:REFRAC.GIF (GIFf/JVWR) (00005E5B)
