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> generally lunar are much less freqeunt than solar halos. To my mind that
> is mainly because the conditions for such event are rare, too. You need
> a bright (i.e. almost full) moon and uniform cirrus for a lunar halo
> to be seen at all.
I would say, that there is a period of about one week around full
moon, what is favorable for lunar halos. Pillars are seen also by
crescents. When you plot a frequency on lunar halos by phase of
moon, the curve looks like a brightness curve of Moon.
Marko Riikonen and Jukka Ruoskanen studied about two year ago lunar
halos from films of aurora camera of Finnish Meteorological
Institute. The main purpose of this survey was to find rare halos,
but they also made a statistics of appearance of lunar halos. Even
the moon pillars couldn't recognize from films, some lunar halos
where seen before first quarter/after last quarter.
> So long, I've never seen colored lunar halos, since they are
> *really* rare. In the German network such events are observed
> only a few times per year. I guess it has to do with the
> sensitivety of our eyes: If the light source is too faint,
> we don't see any colors but only black/white images. So
> many lunar halos might in fact be colored, but we
> cannot recognize it in most cases.
All that you said about color sensitivity of eye is true. Still,
I wouldn't say coloured moon halos very rare. Few times a year
you can see at least red-edged lunar halos. Colourfull lunar
halos are rare, I guess. I've never seen lunar circumzenithal arc,
so I can't if it is very coloured.
-VeikkoM-
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