NavList:

Evan McDade, you wrote:
"Just as your posts showed up, I was trying to figure out how to properly calculate refraction. It looks like either the Bennett formula or the FER formula is more than adequate for my low-precision observations. I appreciate the very helpful information!"

Certainly, you're welcome! And a big thank you, also, to Antoine (a.k.a. by his aviation moniker, Kermit!) for bringing up the topic and presenting his useful extrapolation, which is also probably quite close to what you require, Evan.

With any of these refraction "formulae", beware the results below about 2 or 3° altitude since anomalous refraction, which eventually merges with so-called "terrestrial refraction", takes a heavy toll. There is considerable variability in low altitude refraction that cannot be managed by any reasonable procedure. While the physical cause is believed to be well-understood (occasionally complex layering at the lowest levels in the atmosphere), it can't be dealt with in any manageable way in practical navigation observations.

Frank Reed