Re: [PSUBS-MAILIST] Under Water Lighting

[Dan h <machine@epix.net>]

John,

Thanks,  I knew I read somewhere that one end of the spectrum was better than the
other for under water lights.  I didn't remember where I read it, but it was
probably in the borrowed copy of Busby I had.  The thallium iodide lights sound a
bit to exotic for my project but the bluish tint of the newer high intensity auto
lamps are a possibility.  Andre said they require a transformer.  If they're high
voltage, that might be a problem, but I'll look in to it.

Most of the murkiness in the lake water around here is from plant life.   In the
Atlantic, upper east coast, it's just murky too.  I don't think I even want to know
what that's made up of.   ;-)

What do you think about a high intensity lamp, with a slight blue green filter?
Would a filter help or be to counter productive to make a difference in the long
run?

Thanks, Dan H.

John Brownlee wrote:

>         Candle-power (or whatever measure of luminence you prefer) is only
> relevant in that it represents the total amount of light energy being produced.
> A more interesting question is whether that energy will be absorbed or scattered
> by water and particles in suspension, both on it's way from the lamp to the
> object and back to your viewport. Remember, there's two passes through the
> attenuating medium to consider when calculating losses.
>         A blue-green color-temperature is really going to help. As for
> scattering, that depends on a lot of parameters. I know that laser line scanners
> get people around a lot of the problems with incoherent scattering, but that's
> beyond the scope of lamps. :-)
>         Busby waxed poetic about lamps, I believe his recommendation was
> thallium iodide lamps because their attenuation was low. If you can get your
> peak flux around 5000 angstroms you'll get more seeing for your watts of battery
> power.
>
>                                                 Thanks,
>
> --
>                                                         John
>
> John Brownlee
> Chief Systems Administrator
> Scary Monsters Network
> jonnie at scarymonsters dot net