[quote=grin]
well I just sat the mirror up on a chair and taped a spider of a smaller recoil to the tripod and stood it in front of it. Led is SBT-90 @ 12amp
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WOW ! that is 
Looks like a comet 
Thank You for sharing with pictures 
Be careful ! don’t let it get too hot !
I wonder how you could check the throw on it ? You would need to get a 800 meters away to check it !!!
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I can only run it for short periods of time so normally turn it on take the photo turn it off. I will do something about cooling very soon.
This was taken within the beam
The other thing it is a full moon tonight and you have all the ambient light from the town.
When the beam looks like that it is over focused of to far away when the led is too close it looks like a big fat column
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How to stop it from spinning…….( EDITED )
You will need a keyway to keep it smooth, preferably with the ( .187 square key ) key pressed into the full length copper heatsink if possible. Copper is sticky and a key sliding in the copper may hangup more than a key sliding in the bushing in the housing. Also, if you have room to make the bushing close in length ( OR LONGER ) to the diameter of the busing will help eliminate excessive wobble as it moves. A tight slip fit of .0005 or less should be good, start with a tight fit and a coat of high viscosity oil or thin coat of grease to keep it from locking up. If you make the bushing from Nylon or some other dense plastic you may not need oil or grease or worry about dirt or dust getting on the copper and binding or jamming it up. Oil attracts dirt.
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If you do go the other way and slot the full length of the copper heat sink, use a brass or hard plastic key in the bushing to stop sticking. I would use something non metal for the bushing so it does not jam or need oil. 
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I love this thread.
Only on BLF would a member drive 4 hours one way to get a ridiculously large mirror to build an ET spotter 
Man I love this Place!
Thanks for all the updates and all you do.
By the way,
You Won!
Thanks for the good words. I did win 8^)the MF01s is a nice light. I have been thinking about 8th annual comp. Maybe a right angle recoil.
here are the last few of the night
Any plans to get lux measurements so you can know your throw in cd? I am very curious to know the throw of that giant mirror.
May I have some information of your parabolic mirror? Glass, metal, thickness. I will definitely buy something similar in the future.
With an off-axis parabolic mirror?
I considered making one before, never ended up doing it because It was cheaper to just buy a regular parabolic mirror of a larger size and get more throw.,
It’s a cool idea though, never been done before.
Me experimenting with a few options from various brands, making sure they are fully covered with light when using a collar.
Focal length looks to be 400mm but being imperial I would say the focal length is 16 inchs
Crazy 
That’s a great find on the mirror and being able to put it to good use.
1940
C.A.Parsons &Co Ltd
90/408 =? 90 cm diameter and 408mm focal
OB 11624 =? serial number
from wiki pedi
The Company was founded by Charles Algernon Parsons in 1889 to produce steam turbines, his own invention. At the beginning of the 20th century, the company was producing up to 50 turbines a year at its factory in Heaton in Newcastle upon Tyne.
C. A. Parsons and Company was a British engineering firm which was once one of the largest employers on Tyneside. The company became Reyrolle Parsons in 1968, merged with Clarke Chapman to form Northern Engineering Industries in 1977, became part of Rolls-Royce plc in 1989, and still survives today as a division of Siemens.
He also designed special Optics for searchlights:
http://houseofdavid.ca/parsons.htm#searchlight
Some of those photo’s look like some sort of Alien arrival lol! mad……
Kennybobby,
Thanks, saves me doing the search.
90/408
Im not sure they would have been using a metric system then. Usually with the metric system units are not mixed. It would be 90/40.8cm or 900/408mm. I thought it may have something to do with aperture
This was a 5min build to see if the saucepan lid was parabolic seems it kinda is. After reading this on CP fourm it has got me wondering, like a big wok maybe not custom made but will it focus to a hot spot. Anyone could build a mutha recoil on a low budget.
At what point does one need to take precautions not to blind pilots above?
In the general driection of the beams there is a small airport within range of the lights and it shuts about 9pm after that there isnt many planes. If I have them on and see a plane I kill the light. As they get brighter and longer range I have to be more careful. I would like to hire a plane set them up fly over and light the sky up to see what it is like.
What do you suppose the little arrow is meant to indicate? Does it seem to have a different curvature at right angles to the arrow, e.g. vertical plane versus horizontal plane ? See the bold note below.
From the history:
“Parsons introduced many improvements in construction. The silvered side of the glass was protected by a coat of copper deposited electrically, and later on further protection was given by an additional backing of sheet lead reinforced by wire netting. This rendered the reflector immune from damage by exposure to oil fumes, salt water and other destructive influences met with in service. It also greatly reduced the risks of breakage. Indeed, a mirror protected in this way may remain serviceable after being pierced by a rifle bullet or a shell splinter.”
“Parsons, however, did not confine his efforts to the perfection of parabolic reflectors for throwing straight parallel shafts of light. For certain purposes, as for example when a large area such as a harbour or the landing ground of an aerodrome has to be illuminated, what is required is a flat divergent beam. To produce such beams, Parsons invented and devised methods for the manufacture of a most ingenious form of reflector, curved to a parabolic form in the vertical plane and to an elliptical form in the horizontal plane, both curves having a common focus. The parabolic curvature resulted in the light issuing in a beam of uniform depth, while the effect of the transverse elliptical curvature was to cause the rays first to converge into a vertical line at the secondary focus of the ellipse, and then to diverge at a predetermined angle. Searchlights equipped with such reflectors therefore not only projected a fan-shaped beam of the required type, but the whole of the light was able to pass through a narrow vertical slot situated at the secondary focus. Consequently the searchlight could be operated behind a loop-hole where its chances of being damaged by rifle fire would be very slight.”
That’s some beautiful countryside and CRAZY beamshots. Wow 