Re: L-C-II

[Jan Hollan <jhollan@amper....muni.cz>]

Hi Cliff,

I plan to use Radiance for future computations, as an open-source
programme not limited to mswindows, but at first I have to get the
handbook for it (it seems to be not easy to use without that). 

> I will try to remember to send you the screen snapshot showing the
> iso-footcandle image with the report data directly from the
> application.  I do not have it here at work.  This system meets the
> American National Standard for roadway lighting illuminance design
> method but does not meet the Small Target Visibility criteria.  For
> residential lighting where traffic speeds and density are much slower
> than a highway this is design metric adequate in most cases, however.

I'll recompute it with aladan then (if the ge-format data are available),
it might still be an interesting comparison, worth publishing.

> The main difference that I have seen between acrylic and glass lenses
> is that the acrylic lenses tend to deteriorate over time, eventually
> turning a sickly orange color and limiting light output significantly.  
> I have not heard of any iron absorbsion issues with glass lenses, but
> you might be correct with your assumption.

I wrote to AFG about who uses their low-iron glass, so we'll see. On the
other side, luminaire makers (I spoke with a Schréder representative) say,
that nowadays acrylic lenses will remain transparent the same forever,
thanks to UVstabilizers. I don't know if they are true. I recommend glass
as a sure bet. 

clear skies for auroras,
Jenik