some observations (and a question) regarding using the sun as a light source

A little while back I mentioned that my old Violux light source had bit the
dust. For two weeks I've been using the sun as a light source for gum
printing. Strange, but even though I often coat and dry gum prints
out-of-doors, I've never before considered actually using the sun. This has
been a challenging task! Surrounded as I am by trees, it is often hard to
find openings that are large enough for long enough to expose a print.

I was astonished to learn just how bright the sun actually is! Six minutes
under my fluorescent bulbs equals three minutes under my Violux equals about
45 seconds under the noonday sun. But the time of day causes very extreme
variances in the amount of light. A minute at noon might be 4 minutes at
3:00 PM.

A question: Is there some kind of chart I can refer to that will provide a
sort of adjustment factor for the amount of sunlight falling at a given
time? Something that will take into account latitude and the date?
Received on Mon Aug 9 12:02:55 2004