mooi rood is niet lelijk herinner ik me uit de jaren 70 volgens mij, zegt iets over je leeftijd 
Nice beam djozz. Ever have trouble finding a car park?
Not sure what you mean, but I do not have a driving licence, never needed one over here. (I can park a 20 meter steel barge though)
I guess MRsDNF was referring to your āspotting lightā to spot a place for a car! It guess it could apply to the barge too 
Speaking of which, ships often have great spotlights, my cycle trip to work is along a small part of the Amsterdam port and Iām always jealous of those marine mirror lights. They cost a fortune thoughā¦
Yes, quite the modest LED and optics swap with a driver bypass 
I could not get away with working on my dinner table. I have an Ikea Bjursta wall-mounted drop-leaf table next to my PC desk. It gets a bit cramped sometimes (about 90x50cm work area), but I quite like it. And it allows me to conduct mid-project research on BLF by simply turning in my computer chair, when I inevitably bugger something up
Very cool
Holy spotlight ā¦ Batman
Throwtest
For who is into throw distance as unit (distance at which the illumination is reduced to 0.25lux AKA moonlight level), that is 4.36 km.
My Extech LT45 over-reads a bit, the Tasi 8133 makes it 4.24 Mcd but that may be under-read again. Letās agree on rather throwy
(I do not dare to use my Mobilux classA luxmeter too much lately because the cable-connection to the sensor is rather worn-out and fixing it will require a completely new calibration as well, which will cost me 300+ euros)
Outstanding! 
Great work, once again!!
For the Americans, 4.36km is about 2.7 cheeseburgers per bald eagle miles
I could go for about 2.7 cheeseburger right about now! 
Where did I put that bald eagle?
So much throw, nice work!
Would These parabolic reflectors be appropriate for making somthing like this ? It doesnāt look very expensive. If I understand correctly the short focal lenght means that all light would be collected (expect in center), also it would not produce chromatic aberation as opposed to the fresnel lens.
those are uncoated aluminium reflectors, good for focusing sunlight for heating up stuff, but how is the light loss, and are they optical quality? If yes, they should be fun to make a recoil thrower with
Iām very impressed by the optical performance of these budget plastic fresnel lenses btw, the throw per surface area is very similar to the GT reflector. What helps is that the light source is small and centered (as opposed to projecting an image i.e. a slide which is a large source), the fresnel rims are only maximally optimised for light coming right from the focal point which is the case with a led.
Excuse my ignorance on these calculationsāi see how you calculated the luminous intensity in candela, but i struggle to understand how the Luxmeter sensor area or solid angle come into play, or if they do? Does the sensor area not matter?
If the sensor area were known, would it be possible to calculate the lumens of the beam?
I measured the luxvalue in the hotspot at 12.33 meter, then calculated that back to 1 meter to get the candela-value.
Iām not sure what āsolid angleā is, and the sensor area does not matter as long as it is more or less uniformly lit, as is the case because the hotspot is way larger than the aensor area.
Please excuse if this is off topic, i was puzzled by the calculation. But after a little study it makes more senseāthe lightmeter is calibrated to provide a Lux value for a 1 square meter area at the sensor and not just for the tiny sensor area.
Lux is a measure of the light energy hitting a target area. The units of Lux are lumens/mĀ², where lumens is a measure of the light energy known as luminous flux, with units of cd-sr, candela-steradians. And of course area is measured in square meters.
Steradians are a unitless measure of solid angle, symbol Ī©, which is the angle from the apex (light source) subtended by the area of the target.
i was assuming the target area was just the tiny sensor area, but it is effectively a 1 square meter target area. So the solid angle Ī© subtended at 12.33 meters away is Ī© = Area/distanceĀ² = 1mĀ²/(12.33m)Ā², or the target Area = Ī© ć»(12.33m)Ā²/1mĀ²
So to convert: lux = lumens/Area = candela-steradian/ Ī© ć»(12.33m)Ā²/1mĀ² ;
and solving for candela = lux ć»(12.33m)Ā²/1mĀ²
No matter how impressive the numbers are - the bat signal trumps everything !! 
Great project djozz
First class build djozz
I had no conception what a Fresnel lens can do until your build. Iām still new here and very impressed how well this works.
Every part of this build is very clean and neat. Great build work djozz