Reply To: Practice sights for a beginner.

[David Williams]

Hello Mr ozobozob
This all began when I attempted to do sights in late evening with the artificial horizon. Flashlights did not work. So, I tried a red LED taped over the hole pointing down into the hole. With two AA batteries, I burned out several LEDs. I purchased a pack of LEDs. Then I read the instructions on the LED package. I learned that I burned out the LEDs because of too high a voltage, and resulting current. I measured the resistance required to achieve less than burnout current and it turned out to be about 50 ohms. So, I assembled a 48ohm resister (the only one available) in series with the batteries and the LED, and the light worked very well, but it was too bright. Then I got the idea to vary the intensity, so I put a miniature 5k pot in series with the resister. That way, when the pot is set to zero the LED is protected. I then mounted the LED, resistor, and pot onto a small ¾ inch square block of wood and glued them down tight. The block of wood was shaped to fit snuggly to the artificial horizon, held in place with a rubber band, to enable movement over the hole. To get battery power, I cut into the lead from the handle of the sextant and attached a 1/8 inch audio connector, male and female, to enable mounting and unmounting the configured artificial horizon assembly. To change between it and the telescope is easy, and artificial horizon does not affect the performance of the sextant, other than basic IC. The entire gadget cost less that $5.00. It does work well, but there are internal reflections which can be adjusted by moving the block accordingly.
Hope this helps.
Mr. Williams.