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Re: (meteorobs) Moonlight observing (Leo)
Hello Marco,
just a few comments of mine to your valuable hints.
> Also, it is worth moving to a dark spot on the countryside. A common
> mistake made is that people think that is no use because the moonlight is
> so severe that citylight is no longer a problem. But that is not true.
> These things work cumulative: so moonlight+citylight means you are much
> worse off then moonlight alone.
it's always good to move to a dark site. However, especially in
moonlight condition it is less problematic if you choose a site that is
not 100% perfect, I think. Moonlight and city light are probably additive,
but not linearly. If you take two light sources of the same brightness
instead of one, it will not become double as bright.
> Much depends on the sky condition. Slight haze is deadly with moonlight.
I pefectly agree with you.
> Now, the moon is much less restricting than most people think. There is a
> notorious problem among observers with moonlight conditions: they start
> to UNDERESTIMATE the limiting magnitudes. This is psychological: they
> think that the LM cannot be high, so they put less effort in counting or
> are suspective of 'high' Lm counts. So, you frequently see Lm's reported
> of 4 or 3.5 notwithstanding a clear sky.
> In reality, Lm's with moonlight easily reach 5.0, and often higher. 5.3
> is my typical count, but under very clear conditions I have also got to
> 5.9. When you have clear moist-free skies, be suspective about Lm's lower
> than +5.0:these are most probably underestimated.
Let me support this statement with another example for the Orionids '97.
I watched the shower under really clear skies. I faced almost directly at
the moon (located in Gemini) as I had no other choice, and observed from
the border of the city of Aachen. Still I recorded 5.4 mag some 10 deg (!)
away from the moon, and 5.9 mag some 30 deg away. For me this was only a
loss in lm of ~0.5 mag compared to a darker site without moon!
Sirko
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