Looking for recommendations for a new light fixture

"Thomas Bartkus" wrote in message . ..
"Steve" wrote in message
...
On Mon, 19 Jun 2006 07:14:46 -0500, "Pszemol"
wrote:

This is agains the physics of light reflection theory.
Majority of light will be reflected from the water surface
and hits the walls, suffit of your room.

Are you saying that the beam needs to be vertically down at 90 deg to
the water surface for good efficiency? I was not aware that there
would be huge differences,

I don't know if he's saying that or not. But it would be wrong. You can't
really "beam vertically down" because you don't have a coherent beam. It's
not a laser. You have an immense multiplicity of "beams" leaving the
fixture at every possible angle. You might get a small increase in
perpendicular "beams" striking the surface if set the reflector vertically.
But it is unlikely to be by much.

Well, the goal in building a good lamp fixture is to aim
as much light as possible going stright from the lamp...
Not at the angle.
The goal is achived by making a source of light as small
as posible, being close to the point source, and to place
this light source in the focal point of the parabolic
reflector...

And this is not a problem it is not a laser.
We do not care if the beam is coherent or not...
We do not care even for light to be monochromatic, since
the reflection ratio or the angle of the polished aluminium
reflector is pretty much the same for any color...

What is the problem in an ordinary lamp is the light source
which is not an ideal point source but usually a quite large
bright spot.
In case of HQI lamp it will be this electric arc in the
ceramic bulb of the size of 1/2" or so... and this is much
easier to focus than the light coming from a fluorescent tube.

If we could get a point source of light and place it directly in
the focal point of ideal parabolic reflector we would get a nice
beam of parallel rays of light coming out of the lamp fixture...

Basic principle is shown on the picture below:
http://www.btinternet.com/~k.trethew...ng_systems.htm

I find it humorous the way the CatoptricReflector1.jpg is
drawn in such a way that it is misleading with the light
rays not all coming at a 90 degree angle from the light
source.

Wayne Sallee
Wayne's Pets




Pszemol wrote on 6/19/2006 3:46 PM:
"Thomas Bartkus" wrote in message
. ..
"Steve" wrote in message
...
On Mon, 19 Jun 2006 07:14:46 -0500, "Pszemol"
wrote:

This is agains the physics of light reflection theory.
Majority of light will be reflected from the water surface
and hits the walls, suffit of your room.

Are you saying that the beam needs to be vertically down at 90 deg to
the water surface for good efficiency? I was not aware that there
would be huge differences,

I don't know if he's saying that or not. But it would be wrong. You
can't
really "beam vertically down" because you don't have a coherent beam.
It's
not a laser. You have an immense multiplicity of "beams" leaving the
fixture at every possible angle. You might get a small increase in
perpendicular "beams" striking the surface if set the reflector
vertically.
But it is unlikely to be by much.

Well, the goal in building a good lamp fixture is to aim
as much light as possible going stright from the lamp...
Not at the angle.
The goal is achived by making a source of light as small
as posible, being close to the point source, and to place
this light source in the focal point of the parabolic reflector...

And this is not a problem it is not a laser.
We do not care if the beam is coherent or not...
We do not care even for light to be monochromatic, since
the reflection ratio or the angle of the polished aluminium
reflector is pretty much the same for any color...

What is the problem in an ordinary lamp is the light source
which is not an ideal point source but usually a quite large
bright spot.
In case of HQI lamp it will be this electric arc in the
ceramic bulb of the size of 1/2" or so... and this is much
easier to focus than the light coming from a fluorescent tube.

If we could get a point source of light and place it directly in
the focal point of ideal parabolic reflector we would get a nice
beam of parallel rays of light coming out of the lamp fixture...

Basic principle is shown on the picture below:
http://www.btinternet.com/~k.trethew...ng_systems.htm

"Wayne Sallee" wrote in message ...
I find it humorous the way the CatoptricReflector1.jpg is
drawn in such a way that it is misleading with the light
rays not all coming at a 90 degree angle from the light
source.

The drawing is correct, Wayne!

The light will reflect at the same angle you direct
the light source from the flat surface...

This is exactly how the parabolic reflector works IF...
IF is important: the light source has to be in the
focus poit of this parabole shape...

Of course - reflectors you can buy at the fish stores
are not perfectly parabolic, but they try to estimate
the shape with multiple stright bends of the sheet metal.

Here is a better picture of this process:
http://en.wikipedia.org/wiki/Reflection_%28physics%29

No, not really. Imagine if you were to draw that same
drawing, and you were to make a yellow circle, and then
demonstrate the light coming out of it in all directions.

Wayne Sallee
Wayne's Pets



Pszemol wrote on 6/19/2006 4:56 PM:
"Wayne Sallee" wrote in message
...
I find it humorous the way the CatoptricReflector1.jpg is drawn in
such a way that it is misleading with the light rays not all coming at
a 90 degree angle from the light source.

The drawing is correct, Wayne!

The light will reflect at the same angle you direct
the light source from the flat surface...

This is exactly how the parabolic reflector works IF...
IF is important: the light source has to be in the
focus poit of this parabole shape...

Of course - reflectors you can buy at the fish stores
are not perfectly parabolic, but they try to estimate
the shape with multiple stright bends of the sheet metal.

Here is a better picture of this process:
http://en.wikipedia.org/wiki/Reflection_%28physics%29

That drawing implies that more of the light is reflected
than actually is. Much of it never hits the reflector.

Wayne Sallee
Wayne's Pets



Wayne Sallee wrote on 6/19/2006 5:11 PM:
No, not really. Imagine if you were to draw that same drawing, and you
were to make a yellow circle, and then demonstrate the light coming out
of it in all directions.

Wayne Sallee
Wayne's Pets



Pszemol wrote on 6/19/2006 4:56 PM:
"Wayne Sallee" wrote in message
...
I find it humorous the way the CatoptricReflector1.jpg is drawn in
such a way that it is misleading with the light rays not all coming
at a 90 degree angle from the light source.

The drawing is correct, Wayne!

The light will reflect at the same angle you direct
the light source from the flat surface...

This is exactly how the parabolic reflector works IF...
IF is important: the light source has to be in the
focus poit of this parabole shape...

Of course - reflectors you can buy at the fish stores
are not perfectly parabolic, but they try to estimate
the shape with multiple stright bends of the sheet metal.

Here is a better picture of this process:
http://en.wikipedia.org/wiki/Reflection_%28physics%29

Around 25% never hits the reflector.

Wayne Sallee
Wayne's Pets



Wayne Sallee wrote on 6/19/2006 5:15 PM:
That drawing implies that more of the light is reflected than actually
is. Much of it never hits the reflector.

Wayne Sallee
Wayne's Pets



Wayne Sallee wrote on 6/19/2006 5:11 PM:
No, not really. Imagine if you were to draw that same drawing, and you
were to make a yellow circle, and then demonstrate the light coming
out of it in all directions.

Wayne Sallee
Wayne's Pets



Pszemol wrote on 6/19/2006 4:56 PM:
"Wayne Sallee" wrote in message
...
I find it humorous the way the CatoptricReflector1.jpg is drawn in
such a way that it is misleading with the light rays not all coming
at a 90 degree angle from the light source.

The drawing is correct, Wayne!

The light will reflect at the same angle you direct
the light source from the flat surface...

This is exactly how the parabolic reflector works IF...
IF is important: the light source has to be in the
focus poit of this parabole shape...

Of course - reflectors you can buy at the fish stores
are not perfectly parabolic, but they try to estimate
the shape with multiple stright bends of the sheet metal.

Here is a better picture of this process:
http://en.wikipedia.org/wiki/Reflection_%28physics%29

"Wayne Sallee" wrote in message ...
Around 25% never hits the reflector.

Of course, the rays of light that not hit the reflector
will not get reflected and will travel on the stright
route from the source. But how can you tell it is 25%
or 75% without knowing how good your reflector is ? :-)

Wow that's quite a stretch of the subject of the
indifference being discussed about the drawing.

Wayne Sallee
Wayne's Pets



Pszemol wrote on 6/19/2006 5:40 PM:
"Wayne Sallee" wrote in message
...
Around 25% never hits the reflector.

Of course, the rays of light that not hit the reflector
will not get reflected and will travel on the stright
route from the source. But how can you tell it is 25%
or 75% without knowing how good your reflector is ? :-)

"Wayne Sallee" wrote in message ...
Wow that's quite a stretch of the subject of the
indifference being discussed about the drawing.

Not only this - I still do not see this 90 deg
you have mentioned before ;-)

Hey Steve,

That's a cool setup you've got there. Where'd you get that spotlight
fixture?

Marc


Steve wrote:

Well it doesn't answer your particular question, but I've decided that
I definitely won't be using expensive aquarium units myself in future.
I used an inexpensive industrial spot type halide fitting for the
little nano tank I set up last month, it's got a 150W 10K MH bulb
bought separately. It sits well clear of the water and is not likely
to corrode any time soon, I'd seen them used with success over dealers
tanks. There is a bubbler in there, yet the salt doesn't get near it,
even though it's an open setup. Excuse the temporary top up
arrangements etc on shelf above, about to sort out a decent auto topup
for it and tidy up.

http://www.risedale.com/nonpublic/tank01.jpg

Steve

--
Business Page: http://www.sparklingfloorservice.com
Marine Hobbyist: http://www.melevsreef.com
Reef Podcast: http://www.reefcast.com
Co-Author of: http://reefkeepingbasics.com/ml.htm