Super cheap beam expander!

[xxspeeddemon69x]

im using a different monocular i had already and what direction should the lens face when gluing it to the outside and also what do i do with the other slightly thicker lens that came out with the small one

i have already removed the prism and just dont want to mess this up your help is greatly appreciated :thanks: in advance and apologies for the noob questions

 

[crazyhobo]

I honestly have no idea. The only experience I have is with the Brunton 7x18, which only has two lenses in it. Maybe someone with more knowledge of optics can chime in.

 

[xxspeeddemon69x]

i have the two above lenses and the bigger almost quarter sized one any help from anyone would be much obliged its ok if it doesnt work it was just siting around anyways

 

[steve001]

i have the two above lenses and the bigger almost quarter sized one any help from anyone would be much obliged its ok if it doesnt work it was just siting around anyways

It's really quite simple once you learn about Keplerian and Galilean beam expanders, just Google both terms and you will find sites easily. Many have drawings.

 

[Alaskan]

I bought a monster plano-convex lens with low loss for 800nm to make my own beam expander, it has a long focal length too, now to find the right negative lens and match them up

This is a 28 cm lens, about 11 inches diameter.

Why would I want to play with invisible light? It's not invisible if you look at it with a CCD camera!

 

[crazyspaz]

holy s$@# that things enormous :O

 

[Alaskan]

That isn't so big, this is bigger, got this one yesterday too:

Edit: it needs repair from a bad scuff but have a specialist already agreeing to grind and polish this 30 pound monster for a longer focal point but the work is not cheap at 1,000 dollars, beats paying the going price for a new 13.5 inch diameter lens, if you can even find one. The outside diameter of the mounting structure is 14.75 inches, not counting the posts! I could just as well find a used telescope mirror and make a laser beam expander with that, but I like refractors. Also, finding a super long focal length in a telescope mirror isn't common either, so I opted to just have this one reworked into the focal length I want.

I'm not looking for perfectly spread IR light, just a lot of it in a collimated beam. I don't know if this can be used at 808nm yet, if not I will use it in the visible light range as a beam expander, possibly even a camera obscura. I bought this because of the possibilities, as soon as I learn how well it will pass 800nm I will make that decision and have it cut and polished accordingly. I'm hoping it has relatively low loss for IR, don't know yet as it is still on the way to me in the mail. This is a plano-convex lens, or flat on the other side and 3.5 inch thick in the middle from back to front..

 

[Jmillerdoc]

And I thought I spent a lot on this hobby....

That isn't so big, this is bigger, got this one yesterday too:

Edit: it needs repair from a bad scuff but have a specialist already agreeing to grind and polish this 30 pound monster for a longer focal point but the work is not cheap at 1,000 dollars, beats paying the going price for a new 13.5 inch diameter lens, if you can even find one. The outside diameter of the mounting structure is 14.75 inches, not counting the posts! I could just as well find a used telescope mirror and make a laser beam expander with that, but I like refractors. Also, finding a super long focal length in a telescope mirror isn't common either, so I opted to just have this one reworked into the focal length I want.

I'm not looking for perfectly spread IR light, just a lot of it in a collimated beam. I don't know if this can be used at 808nm yet, if not I will use it in the visible light range as a beam expander, possibly even a camera obscura. I bought this because of the possibilities, as soon as I learn how well it will pass 800nm I will make that decision and have it cut and polished accordingly. I'm hoping it has relatively low loss for IR, don't know yet as it is still on the way to me in the mail. This is a plano-convex lens, or flat on the other side and 3.5 inch thick in the middle from back to front..