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Why does my this happen?

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Hydrogen

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I have a 6" Newtonian telescope and when I point it into the primary mirror and then back off the secondary then into the eyepiece (actually without an eyepiece) it makes the beam brighter and the beam thinner, is there any way to make it burn, because I heard if you can focus the spot incredibly small it burns more (same as a magnifying glass and the sun).
 





Hydrogen said:
I have a 6" Newtonian telescope and when I point it into the primary mirror and then back off the secondary then into the eyepiece (actually without an eyepiece) it makes the beam brighter and the beam thinner, is there any way to make it burn, because I heard if you can focus the spot incredibly small it burns more (same as a magnifying glass and the sun).
Click to expand...

When you point WHAT into the telescope?????

Jerry
 
LOL, Sorry, a 5mW green laser.

it's probably the way the mirror is concaved to reflect light into the aperture.
 
the telescope acts like a beam expander. the magnifying glass makes the dot tighter.
 
It expands if you put the laser in the eyepiece, if you reflect it on the primary and back out, the beam goes thinner and brighter.
 
I'm assuming your talking about a green laser. Even if you are not... those lenses inside your telescope are not made to pass one wavelength. 5mw of light is not enough to burn anyhow... People have popped balloons but it wont burn... I suggest if you want to burn things to buy a lighter or a better laser 50mw+. Also I must add that there are multiple optics in your telescope meaning this will add to the amount of light absorbed by the glass/coatings if any and the optics will reflect more light out... So in reality your probably getting 5mw of focused light. A magnefying lenses is better for burning because it will not absorb as much.
 
jeffreythe00 said:
I'm assuming your talking about a green laser. Even if you are not... those lenses inside your telescope are not made to pass one wavelength. 5mw of light is not enough to burn anyhow... People have popped balloons but it wont burn... I suggest if you want to burn things to buy a lighter or a better laser 50mw+. Also I must add that there are multiple optics in your telescope meaning this will add to the amount of light absorbed by the glass/coatings if any and the optics will reflect more light out... So in reality your probably getting 5mw of focused light. A magnefying lenses is better for burning because it will not absorb as much.
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How can I get my 5mW to pop a ballon, the regular magnifying glass?


Thanks for your reply.
 
I'd assume you would first need a over inflated gallon and a black dot on it. You would then use your lens and make the dot as small as possible and then need to get the focus perfect and hold it perfectly still... Even then you its extremely hard. You also need to make sure your laser is not under 5mw or less... let me find the video.
 
Merged consecutive posts

OK, thanks for the info, my laser is seeming to dim while I turn it on, I know this is normal, but I just put fresh alkaline AAA batteries, and it is very bright then dim, and then dims to nothing at all, wth?

And this laser doesn't even have a sticker on it identifying the wavelength (although it's green), and the output mW. It was stated as 5mW.
 
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all cheapo green lasers are 532nm. Now your laser may dim due to many reasons. Those are cheaply made and constructed poorly as well... In some cases new batteries help... in other cases your laser will warm up causing the crystals to loose their efficacy. I suggest you place it near aomthing cold... Like on a piece of frozen meat or a cold drink. Usually if you cool off your laser it will output more light and stay bright longer. I don't suggest putting in the freezer or refrigerator due to the extremely humid environment but just cooling it down may help. Green lasers are very sensitive to temperature. Try letting it cool down below room tempature and see if it helps a little.
 
Hydrogen said:
OK, thanks for the info, my laser is seeming to dim while I turn it on, I know this is normal, but I just put fresh alkaline AAA batteries, and it is very bright then dim, and then dims to nothing at all, wth?
Click to expand...

Welcome to the world of cheap non-temperature stabilized DPSS lasers. Pretty much all pen style DPSS lasers will vary their output as their temperature changes. How much usually depends on how well built the modules themselves are.. and the better built the modules, the more expensive they are. However none will be totally stable over all temperatures. If you want that, you need one with a TEC.. which would mean it won't be a cheap pen.
 
A telescope mirror used the way you did is the reverse of a beam expander so yes the beam is thinner, at least until it passes through the focal point, then it will expand, but a telescope mirror has a long focal length compared to any magnifying lens... Also, a lens will focus the IR and green light at different focal lengths, but a mirror has the exact same length of focus for all wavelengths, this I think c/b important in your experiments... ;) -Glenn
 
jeffreythe00 said:
I'd assume you would first need a over inflated gallon and a black dot on it. You would then use your lens and make the dot as small as possible and then need to get the focus perfect and hold it perfectly still... Even then you its extremely hard. You also need to make sure your laser is not under 5mw or less... let me find the video.
Click to expand...

This reminds me of just how lame hobby-laser burning really is.
 
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