Sticking his neck out - again

To: Aquatic-Plants at actwin_com
Subject: Sticking his neck out - again
From: Erik Olson <eriko at wrq_com>
Date: Sun, 10 Nov 1996 18:22:14 -0800 (PST)
In-Reply-To: <199611102039.PAA11507 at looney_actwin.com>

> From: JOlson8590 at aol_com
> Date: Sun, 10 Nov 1996 14:56:23 -0500
> 
> TO MEASURE LIGHT LEVELS CHEAPLY:
> Do you have a 35mm camera with a built-in light meter?
...
> the camera in or out of focus, whatever. Whatever you decide, DO NOT change
> the camera position or the focus while you make changes to your lights.

If you have a waterproof 18% reflectivity gray card, you could do
comparative checks between tanks as well. Just stick the card in the
area of the tank you want to measure :)

> SUBJECT CHANGE:  Food for thought.  If white paint is really a better
> reflector than aluminum, why isn't the Hubble Space Telescope Mirror coated
> with white paint instead of aluminum?  

In my previous life as a physicist, we worked with ballon payloads that
were sent up for weeks above antarctica.  The top 3 reflective surfaces
were white paint at 90-something percent reflectivity, aluminized mylar
(somewhat better and more costly) and silverized teflon (99.something
percent reflective and several hundred dollars per square yard).  In the
critical components, they used the teflon, but everything else was
painted.  But certainly I've found a straight metal reflector gets hotter
than a white-painted one.  Good point about the scattering, btw.

  - Erik

---
Erik D. Olson					         amazingly, at home
eriko at wrq_com