[Phys-L] Re: Hours of sunlight

[Rick Swanson <swansonr@SANDHILLS.EDU>]

Or ... you could ask the people who really know what matters -- your local gardening experts, who will probably tell you to watch the site during the different seasons.

I would recommend a book used by our landscape gardening department: Ortho's Complete Guide to Vegetables, by Jacqueline Heriteau.  The second capter is on "Light and Site."  There are other considerations than just the amount of direct sunlight.  For example, "Reflected light can greatly increase the potential of an area that seems too shaded for food plants.   The usual sources of reflected light are white and pale-colored walls and expanses of glass and water.  You can create reflected light by whitewashing a wall or fence."  Another example would be that mid-morning sun can be better than afternoon sun in warmer climates, since afternoon sun may tend to overheat the garden.

Cheers,

Rick

Richard E. Swanson, Ph.D.
Dean of Instruction
Physics Professor
Sandhills Community College, Pinehurst, NC 28374
swansonr@sandhills.edu (910) 695-3715

> > > betwys1@SBCGLOBAL.NET 11/23/2005 9:22 PM >>>
At 01:11 PM 11/23/2005, you wrote:
> Howdy-
>
> Say I want to know the number of hours of sunlight
> that a spot in my garden will get over a day. Say I am
> not largely worried right now as to the total energy,
> just the amount of sun.
>
> If the spot is flat and there are no nearby walls, I
> can figure the hours of light by looking up the
> sunrise and sunset times and subtracting.
>
> On the other hand, if there are nearby walls and
> trees, I need to know the angle of the sun off the
> horizon and the sun's path, the height of the wall and
> distance to my patch of ground, and a bunch of trig to
> figure out how much sun the area gets.
>
> Does anyone know of a resource to help me make these
> calculations?
>
> Marc "Zeke" Kossover

The astro-compass was and apparently still is a handy tool
for making such determinations. It is set for the latitude
etc., and sights the limits of visibility on the ecliptic
(at least, I THINK that's the plane in question).


Brian Whatcott    Altus OK    Eureka!
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