For additional information. The first thing you see on a very clear night,
when the clouds are reflective overhead of the light source, and/or when the
distant light is very strong, is 'light loom.' That's the reflection of the
light up into the sky and what you are seeing is not in direct line of
sight. Altitude off the surface of the water still counts though so the
higher you are the better off you are. The reflection can be of lights 30
to 50 miles off depending on the source. For example the lights of Miami,
NewYork, Los Angeles or any other big city. On a good viewing night loom
from Miami area can be seen out as far as the Bahamas. Normally though you
are seeing light loom from a ship and the brightest lights are, invariably,
fishing vessels. They use strong deck lights when night fishing for these
reasons. Illuminate the deck working area, show they are 'shooting nets'
and sometimes to attract the fish. As the light source draws near we see
the source directly from our 120' vantage point out a bit further than 24
miles due to the combined heights. The higher the light source the farther
we see it. One light, on the top of a mountain in the Canary Islands can be
easily seen from our bridge wings at 40 miles and that's further than our
radars will operate. Of course the light is many hundreds of feet above us.
Light loom, under good viewing conditions, is a good advance indicator of
things to come. Early warning device as it were. Multiple light looms
often help us navigate between those rock filled waves (straits for
example) or give warning of increased surface activity ahead (such as the
fishing fleets around the entrance to the Med, both ends of Suez, the Red
Sea etc. On a lower to the surface sailboat I couldn't hope to see at those
distances BUT by using light loom reflections I can increase my range of
visibility in many situations beyond simple direct vision. A useful tool at
the very least.

M.


"Bart Senior" wrote in message news:EW%Fc.13086$kz.3
...
You didn't account at all for the curvature of the earth.

Yes, I do prefer more complete answers. The idea here
is to pass on information to other readers. Details count.

Nav wrote
It is remarkable that you prefer a long winded yet incomplete answer to
that which gives _all_ the factors without being longwinded. Was may
answer not precise enough?

Bart Senior wrote:
Same for you. Need a little more detail to get a point for the one
question listed below.

DSK wrote:
Bart Senior wrote:

1 pt each
What are the factors that determine a single light's visible range?

The height and the brightness

To be more precise, the height determines the geographic range while
visible range is limited by conditions as well as luminosity and
colour.

Cheers (call me Nav)