JoeL,

Make up your mind: Is it zero viz or not?
 - If it is not zero viz, then there is no problem and an HID light is the
   ticket.
 - If it is zero viz, then holding the light up to your mask will
   not blind you. Try it. It works.

Since you are picking nits, let me explain that I am not suggesting that
you hold the light to your mask and keep it there permanently, just long
enough to determine direction of flow. As far as backscatter, the HID
light appears to be much brighter because of the high frequency spectrum
of the light that is produced. This apparent brightness does not produce
much backscatter.

-JOhn


On Mon, 8 May 2000, Joel Markwell wrote:

> on 5/8/00 3:06 PM, John R. Rose at rose@CS*.SC*.ED* wrote:
> 
> > As long as you have a working light and there is water flow, you will have
> > visual cues. Hold the light right up to your mask. No matter how chocolate
> > babyshit whatever, the light right up against your mask will allow you to
> > see the movement of particles. Certainly if there is no perceptable water
> > flow then this is a mute <sic> point. This is not hearsay. This is my
> > experience.
> 
> John,
> 
> So your advice to a cave diver is to hold a HID up to his face? Eyes open or
> closed? <g>
> 
> Determining water flow by blinding oneself does not sound like much of a
> solution.  If, as you suggest, you're looking for "cues" to flow in a medium
> to high  flow cave aren't there better ways? Can you think of any?
> 
> How would one determine flow in a medium to high-flow cave in zero
> visibility?
> 
> More to the point, my solution has been to get on the line in the proper
> orientation, get in touch contact with my buddy and either continue if the
> vis was planned for or negotiable or exit if not. During the progress in
> either direction the vis is likely to improve unless one is "riding the
> cloud" in which case there are likely going to be moments of swirly vis that
> pops up. During which any light might help. You contend that the HID light
> is useful under these conditions. I have to wonder if the backscatter in
> near-zero vis trying to find vis might not do more harm to one's vision than
> good.
> 
> Not having dove an HID light in zero and/or low vis I'll rely on your
> experience in this area. I think suggestions that can impact one's ability
> to keep breathing should be that accurate.
> 
> Later,
> 
> JoeL
> 
> 

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