LED STAR LIGHTS

Everyone knows that one's night vision, once obtained, is precious to the astronomer.  
Hence the use of red light for required seeing around the observation site.  The purer the 
red the less destructive it is to one's night vision.  This was usually accomplished by 
painting the flashlight bulb with red nail polish producing varying results.  Over the last 
few years the use of LED (light emitting diode) lights has become popular and with good 
reason.  The red is very pure and the power consumption is low thus extending battery life 
to its maximum.  However the $20-$30 price tag has not been overly attractive.  

Well after searching electronics and hardware stores and I was able to build a few different 
configurations for between $3 to $8.  The difference in cost directly attributed to the 
intensity of the light.  

The general procedure is to take a standard flashlight and replace the standard incandescent 
bulb with a red LED and resistor circuit  ( shown below).
	
				   33 ohm resistor

                        _______________XXXXX______					         
			                          |
					          |
			3 VDC  		          O  LED
				                  |
					          |
                         _________________________|
	
Radio Shack sells a variety of LED's ranging from 5 to 5000 mcd (millicandelas - a 
measure of brightness) that should fill all your observing needs with 500 mcd being the 
minimum for outdoor use.  

A LED will only light when current is applied in the correct direction.  The long lead is 
positive.  

The best light I was able to obtain was from Radio Shack ( Bell Road if your here in 
Phoenix) called Slider by Phillips $1.99 on sale.  It has a large efficient reflector handy on-
off switch and best of all soldered wire leads to the bulb.  These connections made it a 
snap to add the resistor instead of having to deal with those funcky spring clip 
arrangements on most lights.  Simply remove the bulb and super glue or epoxy (or both) 
the LED in place solder the connections and you have a pure red star light for a low price 
that will last.

	Slider Flashlight	$2.00
	2000 mcd LED            $1.69
	100 ohm resistor        $0.15

If you need more light they have a 5000 mcd for $4.99	.


THE SLIDER LITE IS 4.5 VOLTS. BELOW IS THE RESISTOR VALUES
FOR VARIOUS VOLTAGE CONFIGURATIONS.

3 VDC -	33OR 47 OHM  1/4 WATT
4.5 VDC - 100 OHM 1/4 WATT
6 VDC - 150 OHM 1/4 WATT
9 VDC - 270 OHM 1/4 WATT
12 VDC - 390 1/2 WATT

Other possibilities are LED's over your setting circles or lens rack powered by a common 
battery located on your mount or tripod.  Variable resistors (potentiometers) added to the 
circuit to adjust the brightness.  Inexpensive pure red light at your disposal.  Use your 
imagination.

					Kevin Gill
					Cave Creek, AZ