photoperiod civil or astronomical twilight ?

FLECKENSTEIN, JOHN JOHN.FLECKENSTEIN at dnr.wa.gov
Thu Jan 18 11:12:27 EST 2007


Friends,
I know that among the bats (often seen as the enemy, but interesting in
their own way), different species begin their activity at different
light levels.  I suspect that among the species of leps you would find a
broad range of determining factors.  Detailed studies of a few species
might be an interesting place to start.

John Fleckenstein, zoologist
Washington Natural Heritage Program
Olympia, Washington, USA

-----Original Message-----
From: owner-leps-l at lists.yale.edu [mailto:owner-leps-l at lists.yale.edu]
On Behalf Of Michael Gochfeld
Sent: Thursday, January 18, 2007 7:24 AM
To: loeches at fbio.uh.cu; Leps-l
Subject: RE: photoperiod civil or astronomical twilight ?

Do you have a priori hypotheses or beliefs about how light effects
whatever it is you are looking at or for.  Also whether wavelength
(color) or brightness alone matter. 

Also whether looking at diurnal animals vs nocturnal ones. I would
imagine that they respond to very different cues. 

If I were doing field work myself I would use some kind of photometer.
I have used various simple light meters but there are recording
photometers which are very nice.  For butterfly work, we also worry
about sunlight per se, not just brightness. 

So I, at least, don't have a straightforward answer to what seemed at
first like a straight forward question.  Have you considered nautical
twilight as a compromise (outlines visible, but not details). 

Since cloud conditions around sunrise or sunset have a substantial
impact on brightness, it would be necessary to take that into
consideration if looking at a short-term event.  MIKE GOCHFELD




-----Original Message-----
From: owner-leps-l at lists.yale.edu [mailto:owner-leps-l at lists.yale.edu]
On Behalf Of loeches at fbio.uh.cu
Sent: Thursday, January 18, 2007 8:18 AM
To: Leps-l
Subject: photoperiod civil or astronomical twilight ?

Hello comunity,

I would like to know which is more appropiate to use for studies about
photoperiod in insects and amphibians, the civil twilight or the
astronomical twilight ?

Thanks,
Laura


 
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