Paul Schlyter Apr 29, 2001
>> Clearly the rise/set of the upper limb more closely resembles theYou're absolutely right! The difference would be quite small anyway,
>> visual impression of an observed rise/set: we think the "sunrise"
>> occurs when we see the first part of the solar disk, not when we see
>> precisely half the solar disk. However, when we use the upper limb
>> of the Moon to compute lunar rise/set times, we encouter a problem:
>> the upper limb of the Moon is fairly often dark! The "proper" way to
>> deal with that is somewhat complex though: one could compute the
>> rise/set time of the uppermost part of the ILLUMINATED portion of the
>> lunar disk. I've never seen any program or heard about anyone
>> actually doing this though.
>
> I don't think there would be any practical benefit in attempting to do this.
> Rise and set times can only realistically be calculated to an accuracy of
> the nearest minute or so anyway, due to the uncertainties of refraction in
> the "real world" which can vary significantly over a very short timescale.
> This would be an exercise of purely academic interest, IMHO!