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[DSLF] Digest Number 1456

There are 2 messages in this issue.

Topics in this digest:

      1. Re: definitions
           From: Bernard Kosicki <kosicki@ll....edu>
      2. Re: definitions
           From: Steve Davis <w2sgd@juno...>


Message: 1         
   Date: Wed, 22 Sep 2004 14:58:42 -0400
   From: Bernard Kosicki <kosicki@ll....edu>
Subject: Re: definitions

At 11:39 PM 9/21/2004 -0500, you wrote:

>  > It is
> > pointed out, as Gail suggests, that an FCO luminaire also is Fully 
> Shielded.
>Over the years I have collected a number of photos illustrating light
>trespass, and some of the big offenders include improperly placed FCO
>Given that, shouldnt a time-tested definition of 'fully shielded' be
>based on outcome performance rather than stock, off-the-shelf luminaires
>marketed as a 'one size fits all' solution?


You are right, of course, that FCO designation alone is not the whole 
story.   To manage glare and light trespass, we need to know how close 
these lights are to sensitive areas, how high they are mounted and their 
cutoff properties.

Peter Talmage and the other Kennebunkport folks recognized this and built 
into their 1992 ordinance their well-known restriction that lights must be 
no taller than 3 + D/3, where D is the distance of the pole from the 
property edge.   This won't completely eliminate light trespass, unless the 
luminaire is cutoff in the direction of the property no more than 71 
degrees (somewhat better than the nominal 80 degrees of an FCO.)

In Acton's new ordinance, we therefore called out for additional shielding 
to accomplish 70 degree cutoff for luminaires closer than D/3 to the 
property boundary to adjacent sensitive properties (public rights-of way or 
residential or conservation land).  We also have a requirement that 
measured light trespass onto such properties be less than a maximum amount, 
as a performance measure.  It is our feeling that performance measures 
alone are not adequate, however, and that hardware specification is also 
needed to be effective.

It would be nice if manufacturers made it easier to find and more prominent 
on their web sites both house side shields, and families of luminaires that 
have sharp cutoffs on one side.  Then, less expert lighting designers than 
make comments in this forum would have better access to these products.

Bernie Kosicki


Message: 2         
   Date: Wed, 22 Sep 2004 16:12:34 -0400
   From: Steve Davis <w2sgd@juno...>
Subject: Re: definitions

Patric wrote:
>shouldnt a time-tested definition of 'fully shielded' be
>based on outcome performance rather than stock, off-the-shelf
>luminaires marketed as a 'one size fits all' solution?

Sounds like real engineering to me -- instead of read label,
purchase, install, and run assuming everything is ok.

The "scientific method" tests and then goes back and fixes
any problems and tests again. -sd

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