On 27 Jan 2005 05:50:38 -0800, "Intertracer"
wrote:

On the cloud tops of Titan there's 72 times darker than on earth clowd
tops.
Earth's atmosphere passes through 63% of sunlight on a shiny day.
Titan's atmosphere is 10 times heavier and passes 10% of sunlight.

After a rough estimation, Titan's surface receives from 1/1000 to 1/500
of light which comes to Earth's surface.

It's in fact much darker than on a very stormy day, it's more like late
dusk, or at night, something like 20-30 meters away from a streetlight.
You'll really need some sort of artificial lighting there to feel
comfortable, and some serious cloth

By my calculation, Saturn (now 9.1 AU from the Sun) receives 1.2% of the
sunlight received at the Earth. The amount of sunlight absorbed is more
difficult to calculate than simply comparing atmospheric density. The
Earth's atmosphere actually only attenuates about 20% of the incident
light, and much of that is scattered, not absorbed. Assuming your value
of 10% transmission for Titan, however, the surface light will be 0.12%
of Earth's. On the Earth, at local noon over the middle and tropical
latitudes, the illumination is about 130,000 lux. So at local noon on
Titan, figure 160 lux. That's quite a bit brighter than a darkly
overcast day on the Earth, which measures at 100 lux, and some 600 times
brighter than the full Moon. Office lighting guidelines normally specify
100 to 400 lux as the target range. Late twilight is normally taken as
10 lux.

In other words, the illumination on Titan would be quite comfortable for
human eyes- no artificial illumination required for most tasks.


Huygens cameras were specially designed to take piclures in such dark
conditions, so don't take those photos literally -- they don't depict
the real ilumination...

Huygens was provided with a light source to use in the event conditions
were very dark. I'm not sure if it was used or not. The camera is quite
ordinary in its sensitivity- just a typical CCD. There is no special
light amplification used. I believe what we are seeing in these images
is pretty much what we would see with our own eyes.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com