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RE: (meteorobs) streetlights in the cold....

Hey... good gif.
My brain just wasn't making sense of 'any' of the explanations given until I
saw it.
So my thanks... too !
Bruce
Computer Hardware Analyst - IS/Field Services
* email:	bruce_musson@dofascodot ca
* tel: 		(905)548-7200 x2388
*  fax:		(905)548-4960



> -----Original Message-----
> From:	Robert Goler [SMTP:robert@neumann.maths.monashdot edu.au]
> Sent:	Thursday, January 06, 2000 12:31 AM
> To:	chris smith
> Cc:	meteorobs@jovian.com
> Subject:	Re: (meteorobs) streetlights in the cold....
> 
> 
> Hi Chris
> 
> I think I know what you are referring to in regards to the columns of
> light from the streetlamps. I have just found a couple of photos which
> show the features quite well.
> 
> Wayne Hally hit the nail right on the head when he mentioned that the
> cause was probably due to flat ice crytals reflecting light back down,
> analogous to a sun pillar. 
> 
> To explain things a little better I have supplied a small .gif piccy which
> shows the situation. The light from the streetlamp gets reflected by the
> flat ice crystals to the observer. The observer sees this reflected light,
> and appears to the observer to originate from high in the sky (the dotted
> lines that trace back away from the observer). Hence the observer sees the
> pillar.
> 
> One thing that is different from the solar pillar is that these streetlamp
> pillars can, in priniciple, have an infinite height, and extend all the
> way to the zenith. This can be seen in the diagram by making the layer
> of ice crystals deeper, or getting closer to the light source.
> The solar pillar, on the other hand, is restricted to a height of about 20
> degrees, but that's another topic. 
> 
> I've seen solar pillars before, but, to be honest, I've never given a
> thought to streetlamp pillars. I suppose that's due to the fact that I've
> never been anywhere where there has been ice crystals so low in the
> atmosphere. This probably explains my tact in earlier emails.
> 
> Cheers
> 
> --
> 
> Robert A. Goler        
> 
> E-mail robert@neumann.maths.monashdot edu.au
> http://www.maths.monashdot edu.au/~robert/
> 
> Department of Mathematics and Statistics
> Monash University
> Clayton, Vic 3168
> Australia
> 
> --
>  << File:  >> 
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