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World's brightest flashlight

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klugesmith

Mon Nov 22 2010, 02:33AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

TDU: with your luxmeter you can determine the candlepower.
Simply measure the lux at distance of say 100 meters (so you're properly in the far field)
and multiply by 100^2.

Re. ISS visibility: I figured numbers similar to Chris's.
I honestly don't want to rain on anyone's parade, but the candlepower aren't that spectacular
because, as TDU says, the LEDs are a diffuse source & hard to focus into a narrow beam.

Half of 84000 lm in a 5-degree-wide beam (0.006 steradians) is about 7 million candlepower.
Companies like to advertise handheld spotlights with higher cd ratings (probably a stretch)
that put out fewer lumens, but tune the optics to make the narrowest possible spot.
Ordinary green laser pointers have comparable candlepower (single digit lumens in sub-milliradian beam).
Trailer-mounted searchlights are in a different class -- you could rent an honest 120 Mcd unit to advertise your event, or summon Batman. Real IMAX projectors (not the lame digital IMAX in shopping mall cineplexes) have a 600000 lumen lamp with source area less than 1 cm^2.

The instant on/off modulation capability makes TDU's LED flashlight uniquely good for, say, signaling to an observer at (or from) a distant mountain. Maybe even in the daytime -- you can aim close enough without needing to see the beam. In the great war, on/off modulation was done with mechanical shutters like Venetian blinds. Please keep us on the news list!

-Rich

Tesladownunder

Mon Dec 06 2010, 01:19PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Chris Russell wrote ...

Time to get in touch with someone on the ISS!

I hope to contact Andy Thomas (Aussie NASA astronaut) sometime once I have a solid proposal for the ISS team to look out from their new cupola.
I would need to servo my flashlight with a small telescope that can be set at least every 5-10 seconds to allow coverage of the invisible ISS position in the 5 degree beam.

Klugesmith wrote ...

TDU: with your luxmeter you can determine the candlepower.
Simply measure the lux at distance of say 100 meters (so you're properly in the far field)
and multiply by 100^2.

Re. ISS visibility: I figured numbers similar to Chris's.
I honestly don't want to rain on anyone's parade, but the candlepower aren't that spectacular
because, as TDU says, the LEDs are a diffuse source & hard to focus into a narrow beam.

Half of 84000 lm in a 5-degree-wide beam (0.006 steradians) is about 7 million candlepower.
The instant on/off modulation capability makes TDU's LED flashlight uniquely good for, say, signaling to an observer at (or from) a distant mountain. ....

I need to get the data from farfield. I have some nearfield readings but they are not really meaningful. At each lens the reading is about 200klx (sunlight 130klx).
Testing a single focussed 100W LED at 25m the meter gave 36 lux. So by your formula candle power is 36*25*25=22,500. Multiplying this by the 15 LEDs gives 337,500. Of course, I need to measure the array directly, but it is a long way from 7 million which I would associate perhaps with a highly focussed HID light. I need to get my head around all these photonic terms.

I have done the video shoot with interviews, overlays and details of the bike, flashlight and Xmas tree with Santa riding the bike. It will be the colors rather than the maximum power that will be the best TV feature of this bike.
Still need to get a good "money shot" still which is tricky with 4 light sources to get right.
Also need to finish off some video of comparative flashlight shots then it's finished.

Here are some data though. Switch on current for one LED is about 7A decaying over 200ms to 3.4A as the ballast filament heats up. Switch on light output (measured by silicon cell) is only up 5% however, so it seems that they are being driven reasonably fully at least individually with full battery charge. Actually I have just realised that was for switching the full array on so the data are not really comparable. I need to recheck this properly.

Chris Russell

Tue Dec 07 2010, 09:40AM

... not Russel!
Registered Member #1 Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052

Tesladownunder wrote ...

I hope to contact Andy Roberts (Aussie NASA astronaut) sometime once I have a solid proposal for the ISS team to look out from their new cupola.
I would need to servo my flashlight with a small telescope that can be set at least every 5-10 seconds to allow coverage of the invisible ISS position in the 5 degree beam.

That would be a really awesome experiment. Many of the astronauts on board will be familiar with Morse code. Perhaps you could relay a brief message to the station using either on/off modulation, or visual FSK (only red, blue, or green on = off, everything on = on). Fortunately, with a five degree wide beam, aiming doesn't need to be too precise.

I don't know if a telescope would be necessary. Amateur radio operators make use of keplerian elements to aim their antennas at orbiting satellites (and the ISS) during passes, which works well even for antennas with a beamwidth similar to your flashlight. A properly calibrated gimbal with markers for elevation and azimuth could allow the flashlight to be rotated through the path of the pass manually. Of course, there are two-axis rotors, but getting one to work with your flashlight might be... problematic.

Tesladownunder

Sat Dec 11 2010, 05:13AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

This is my first distance shot. 2.5km along the straight stretch of Lillydale Rd out of Bunbury.
Photo 1 shows the 1/4 moon for brightness reference and a car heading down that stretch about 100m away. My son's car taillights are in the foreground.
Photo 2 shows the Flashlight firing the white LED's 1200W from 2.5km. The moon has moved to be a bit obscured by trees (long wait for a car free period).
Photo 1 shows the green light alone to confirm the source.

I believe Chris' calculations about 1/2 moon brightness at 10km now. It just didn't seem intuitively right before.

Now I want to try Bunbury to Busselton (up to 45k) but I will need to get a vantage point either end to allow it to get over earth curvature (3.6m drop). This pic of the comet shows a 35 km view to Busselton (horizon lights on left) to Cape Naturaliste lighthouse on right.

1292043684 10 FT97381 Ledflashlightroadtest25kpassingcar

1292043684 10 FT97381 Ledflashlightroadtest25kfull

1292043684 10 FT97381 Ledflashlightroadtest25kgreenfull

Tesladownunder

Mon Jan 10 2011, 06:33PM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

I have received a response from NASA who have forwarded my proposal to the operations team. It's just a foot in the door but is a first step. Fingers crossed from here.

My proposal has been fine tuned significantly since I last wrote and is in detail here on my site.

In essence one plan is to go to a place where there is a 90 degree pass over by the ISS at night. Set up the static flashlight vertically. Brightness based on measured lux values is about that of Canopus, (Apparent magnitude -0.72). Flash a Morse coded message in the 2.5 second flyover with the ISS using their 400mm Nikon D3 with open shutter and not tracked. The Morse code can be read out on the film which provides proof of sighting for Guinness.
There is 8 seconds of visual view time on the ISS with a static flashlight.
Plan B is to have the flashlight track the ISS to get longer visual view times (perhaps 1 minute).

My proposal was:
Subject: Potential publicity photo for ISS. Request night photos of Western AustraliaI have a proposal that may be easy for the ISS to perform and give a nice TV news segment. Also perhaps world firsts such as seeing a flashlight from space or reading Morse code from space.
It is a positive article easily understood by the public and takes only minutes of ISS astronaut time.
I have made the World's most powerful flashlight at around 84,000 lumens nominal. (Guinness Record applied for)
With a 10 degree beam (around 32,000 lumens) this will be visible at ISS altitude as apparent magnitude â€“0.7 at 230 miles altitude which is the brightness of Canopus, the second brightest star.
The thing about this light is that it is bright and being LED rather than incandescent or discharge can be modulated into a morse code, or even an audio signal.
Accordingly a night time ISS pass in astronaut waking hours over South Western Australia in the next 3 summer months (generally cloudless and low population density) would see this.
A long camera exposure (NO tracking required) would therefore present a string of "dots and dashes" on the picture whereas all other lights will be streaks. It should be a striking picture from which Morse code could be read.
I would not need to track the ISS once set up for a single photo still, but would with an accuracy of 5 degrees if it was to be viewed directly by an astronaut as well (preferable).
If this proposal is of interest I can present more solid data, mechanical tracking information, Guinness information and plans for optimal siting for dates and times. In particular aiming for a near 90 degree elevation.
I am an Australian experimenter with a high media profile (eg on Discovery Channel 5 times) and have the resources to make this a success from my end.
My relevant web page and proposal is here:

This shows the relative positions of the ISS (using the Nikon D3 400mm lens) and the Flashlight.

This shows a simulated view from the ISS camera with open shutter for 2.5 seconds showing my flashlight
modulated light amongst the other town/city lights. This will be morse coded to give a brief message.

This is the flashlight viewed from 9km.

The ISS view at 230 miles will be less by a factor of 1700 but still very visible at night to the naked eye.

NASA's response:Thank you for your message. I have forwarded on your request to our operations team for review. Acquisition of specific target imagery from the ISS is dependent on several factors including the crew task schedule, orbital position of the spacecraft, and environmental factors (cloud cover in this case).

The crew does sometimes take imagery of areas outside their standing science targets, and I recommend that you periodically check our online database for night time imagery of the western Australia coastline to see if the Bunbury region has been acquired. You may use our technical search tools at

for this purpose, I would recommend doing a combined Geographic Region and Features search (use the keyword â€œnightâ€ â€“ no quotes required).

We also have an Uncataloged image search tool at

- crew discretionary images as described above are typically not high priority for cataloging, so you are most likely to find new imagery using this tool.

Thank you for your interest in astronaut photography of Earth!
Earthweb
The Gateway to Astronaut Photography of Earth
NASA Johnson Space Center

Chris Russell

Mon Jan 10 2011, 08:19PM

... not Russel!
Registered Member #1 Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052

Looks like kind of a canned response to a "take a picture of my house please" type of request, but it's good to have a foot in the door. Hopefully the next person up the chain will take a closer look at your proposal.

The 2.5km picture is amazing.

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