Hi to everyone. I know this is an older post. but I find it very interesting and informative. Thanks to everyone for sharing their expertise.
For a few years I have been playing with modifying some Chinese White (copies of Photon) microlights for a friend of mine that loves astronomy. These lights normally take 2 CR2016 batteries. With most 5mm RED leds, you use a single CR2032. The CR2032 has around 230mah @ 3 volts, versus the 80mah in a CR2016. A red LED draws about 25-30ma with a new battery. A White LED draws about 65ma with the 2 CR2016. With a single CR2032, the white leds pulls about 7mah. AND are bright enough to read close up and get around indoors. I can't measure lumens, but both the RED and White Led's are way too bright for astronomy use with just the CR2032. I have NOT tried the deep red 680-700nm peak "deep red" leds; but expect that they too might be too bright for best night vision.
I recently took an old GREEN Photon 3 that I had, a replaced the 2 X CR2-16 batteries, with 1 CR2032. The Photon 3 has 3 (PWM) output levels, low medium and high. On low with the 1 CR2032, I can use it to walk around indoors, once my eyes get adjusted to the dark for a minute or so. At full power it will light up a normal size room. At full power it only draws 6-7ma, so batteries last a long time. At low, it might be Ok for astronomy. With a RED led, it would probably be better? (Guess it depends who you ask !) For me, the green on low does not seem to affect night vision for reading or looking around a dark home.
I just ordered some 700nm "DEEP RED" leds. And will replace the green led, with that one. (Need to pull out and solder on the new led). Beause they produce less lumens, I expect that low, or even medium may be Ok for Astronomy. (But will use up batteries a bit faster. )
I also ordered a Photon Freedom to play around with. It has a continuously adjustable brightness, with a low that is lower than the Photon 3's... It's a green one, and again, replacing the 2 CR2016 batteries with one CR2032 gives plenty of light for indoor use. Even though it's Green LED is more efficient (brighter on high) than my old green photon 3; At it's lowest setting it is a lot dimmer than the photon 3 on low. The Photon Freedom with a Green LED will have a battery life of at least 32 hrs on high. (And longer on lower and still useful PWM settings). (32hrs = 230mah/7ma) This will be my Emergency EDC/Mini-Survival kit. With a RED Led, expect 8 hrs of battery life as the led pulls 4 X the ma At full power.
I may try out one of the 700nm led's in the Photon Freedom. Those LED's can be replaced without soldering...
Another recommendation I have, is to roughen the surface of the LED's with 600 grit "wet or dry" silicon carbide sandpaper. You only need about 1 inch square and about 1 minute to roughen up the surface of the LED. This produces a much smoother beam, that is better for area lighting, and for close up reading. (No shadows or streaks).. It also reduces beam "throw", but that's not what I use microlights for... (There are "diffused" LED's available, but the selection is quite limited in beam angle, and color/nm.)
These can be used as a headlamp either using the clip attachment that comes with the photon freedom; OR by using sitck-on Velcro "Dots". One piece goes on the back of the microlight, and the other on your hat's brim, or eyeglasses, etc...