Spider Reflector Angle

[DeepBlueSea]

Setup my 400w MH with Spider Relectors, perpendicular to the tank. However, it seems as though there is a large dead zone right under the bulb. If I flare out the sides of the Spider Relector it seems to brighten up.

Your experiences utilizing Spider Reflectors?
Should I attempt to change the angle?


Deep Blue

[dnjan]

What is the width of your reflector in its normal position? Perhaps it got distorted in shipping. I believe mine was something like 12-1/4" between the mounting holes.

[Bishop]

Unless the bottom of your bulb/envelope is dirty or hazy, then it's got to be a figment of your imagination. :)

the orientation of the bulb matters tho, if the little nipple on the envelope (the internal part of the bulb) is facing down you could get a slight difference.

The majority of light is emitted parallel from the bulb, however, the second it leaves the bulb it loses intensity. Once it bounces from the reflector it has a sharp decrease (infinitesimally speaking) so unless you have two bulbs overlapping, then that area could have higher intensity.

The brightest spot however, will be directly below the bulb.

[DeepBlueSea]

The nipple is facing up and believe me, there is this "shadow" compared to the side's. I'm not saying there isn't light, but there is a definite difference between the sides and directly under the bulb. It's less noticable with both lights on and I submitted the original post with only 1 bulb on. I've placed two clams under the bulb and when I flair out the sides of the reflector its seems to light the entire side of the tank much more evenly.

Wish I had a light meter to measure the difference.

Deep Blu

[AHAB]

I remember reading something in Aquarium Frontiers about a dim spot under the light and hot spots off to the sides.
This is caused by the shape of the reflector.
Maybe someone can find the link to it.
AHAB

[TAC]

Try moving the lamp vertically closer and further from the reflector with it shining on a white piece of paper. See if there is a distance from the reflector that maximizes your light intensity and eliminates the dark spot. There are bound to be some variations since the SpiderLight is not a perfect parabola, but I think I remember reading a post where it was stated that with the lamp at the right distance from the reflector there is not a dark spot under the lamp.

Terry