Telescope to HID Spotlight?

I came across a website with some fairly large telescopes for decent prices and the thought entered my mind that the tubes and mirrors gather a ton of light and magnify it, focusing it in the eyepiece. What do you think would happen if you mounted a 50 Watt HID bulb at the focal point of the telescope? Has anyone ever tried this?

First you burn your eyeball out, then the light will burn a hole through your head.

I've done it with the sun, which is much brighter. It burns little tiny holes not unlike a magnifying glass would.

Is this what you're talking about or something else?

I think what the OP has in mind is not to focus the light through the eyepiece, but to replace the entire eyepiece assembly by placing the light source at the reflector's focal point, and thereby using the reflector to send the light out into space (or whatever target he points it at).

It's actually a pretty good idea, and I think there are some fairly large astonomical-size telescopes with good optical-quality reflectors that can be picked up quite cheaply.

The main problem is that these reflectors are all quite shallow in profile, so only a small proportion of a light source will actually strike the reflector unless it is focussed towards the reflector. Unfortunately in doing that, the point-source of light becomes much larger unless a complicated elliptical focussing system is used, so collimation is difficult.

There's a very good thread here that should interest you, if you haven't seen it, where a relatively shallow-profile reflector is being used.

I tried this once with a 5D maglite and a friend's telescope... took off the eyepiece and stuck the light into the focuser tube. It made a very respectable bright spot on a mountainside about a mile away. Laser beams are made to go further before spreading out by using a similar setup.

DM51 said:

I think what the OP has in mind is not to focus the light through the eyepiece, but to replace the entire eyepiece assembly by placing the light source at the reflector's focal point, and thereby using the reflector to send the light out into space (or whatever target he points it at).

It's actually a pretty good idea, and I think there are some fairly large astonomical-size telescopes with good optical-quality reflectors that can be picked up quite cheaply.

The main problem is that these reflectors are all quite shallow in profile, so only a small proportion of a light source will actually strike the reflector unless it is focussed towards the reflector. Unfortunately in doing that, the point-source of light becomes much larger unless a complicated elliptical focussing system is used, so collimation is difficult.

There's a very good thread here that should interest you, if you haven't seen it, where a relatively shallow-profile reflector is being used.

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Bingo!!! That is exactly what I am talking about. The mirrors are image quality and I would think it would project a very tight beam a very long distance.

http://en.wikipedia.org/wiki/Maksutov_telescope

Thanks DM, I get it now.


I agree that there's a problem. The geometry is fine but the efficiency is poor, especially with a long HID arc as the starting point. I think the main efficiency problem is that you're starting with a very small collection point, that being a secondary mirror, which is gathering minimal lumens, then using the main objective as one big beam expander.

If you could somehow pre-focus a beam of light onto the secondary mirror, similar to how 2 lens DEFT system pre-focuses the light before it hits the back side of the main lens, then you could probably have and efficient set-up but LED's of course don't put out very many lumens, especially small XR-E types.

If a beam of a certain diameter is desired, it's best to capture a point source of light with a single main reflector of proper focal length one time. Still, it's an interesting thing to think about regardless. You might be interesting in checking out the 175W Megaray spotlight, as it uses optics more efficiently to essentially do the same thing.

The DEFT basically works off the same principle in the fact that a quad die LED shines through a lens that sends a perfect picture of the source into the distance for maximum throw in an almost linear fashion.

To have the same principle applied with a 50W HID bulb would take a bigger housing similiar to a telescope tube, but as mentioned there would have to be some serious trial and error to properly capture all the lumens to project forward and not have any waste.

I think its a viable project.... especially if it could be portable... but would complicate things the more. I really don't see why a long tube would be necessary as a short one should work just fine because the first lense would basically capture all the light as with the DEFT.

A pretty cool idea and if mastered would be a big seller.
The Maxabeams do it in a reflector style whereas what we are talking about is more of a projection format.

Funny when you look straight into the lens of a DEFT "without it on of course", it looks like a eyeball with a pupil and an iris surrounding.

I suppose if you took the LED out and looked through it instead, you would have a crude form of a telescope.

Patriot said:

Thanks DM, I get it now.


I agree that there's a problem. The geometry is fine but the efficiency is poor, especially with a long HID arc as the starting point. I think the main efficiency problem is that you're starting with a very small collection point, that being a secondary mirror, which is gathering minimal lumens, then using the main objective as one big beam expander.

If you could somehow pre-focus a beam of light onto the secondary mirror, similar to how 2 lens DEFT system pre-focuses the light before it hits the back side of the main lens, then you could probably have and efficient set-up but LED's of course don't put out very many lumens, especially small XR-E types.

If a beam of a certain diameter is desired, it's best to capture a point source of light with a single main reflector of proper focal length one time. Still, it's an interesting thing to think about regardless. You might be interesting in checking out the 175W Megaray spotlight, as it uses optics more efficiently to essentially do the same thing.

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How much is the MegaRay in US dollars? I couldn't find a price anywhere on the web.

https://www.candlepowerforums.com/threads/46589

Post #9

Back from 2004 but is probably good as a starting point. $6,000

+1 to what BVH said.

I think you have to call to order and it seems like they focus on military sales.

BVH said:

https://www.candlepowerforums.com/threads/46589

Post #9

Back from 2004 but is probably good as a starting point. $6,000

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Only 6K?... Heck if I'd known that.... I think I'll take 7 and give them out for Stocking stuffers!

Anybody else want one for Christmas?.... just PM me your address! :huh:

24" or 60" Carbon Arc, and Lasers. Probably some classified military hardware?

windstrings said:

Only 6K?... Heck if I'd known that.... I think I'll take 7 and give them out for Stocking stuffers!

Anybody else want one for Christmas?.... just PM me your address! :huh:

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That is what I thought. I think you can pick up a decent telescope with a tripod and NO auto search for around $300 if you could make it work.

Juggernaut said:

What throws farther the 175 watt Megaray, or the enhanced output Maxabeam:thinking:?

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Even the standard Maxabeam out throws the MegaRay albeit at 1/2 the lumen output. I believe there are comparison pictures on the Polarion USA website but it's been a really long time since I've viewed them.

Patriot said:

Even the standard Maxabeam out throws the MegaRay albeit at 1/2 the lumen output. I believe there are comparison pictures on the Polarion USA website but it's been a really long time since I've viewed them.

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+1.

The enhanced output MaxaBeam is going to out throw the 175 watt MegaRay by a significant amount. That being said, I would prefer the Megaray's superior light output and it would be the one I would choose if I had the funds to buy one of them.

I know very little about the megaray, but at first glance, its always very hard to outperform larger reflectors with a smaller reflector "or even lens".

It appears the megaray's strong point is its stealth and ability to mount easily on tactical equipment.

At a wow price of course.

I went to the Polarion site and had no luck finding the images. I had planned on posting a link but no dice. I suppose Ken might have them available as a favor if someone needed them. I probably should have saved them all but never planned on them going away.