This seems to be the best option I can find in a pre-made solution. Almost perfect size for the body I have, good focal length, only costs half the earth... I know I can get it in a couple of days, being local to me. Not sure what impact the small hole in the center would have, but I could patch that with some reflective material.
Of course, the other solution is to make something.... after a bit more searching, I came across this site, which made understanding the parabola easier for me.
I'm also planning to make a few cardboard parabola cut-outs that I can take to the dollar-store, in the hope that they may have a dish/bowl that just happens to have a parabolic contour.
That Edmund Optics mirror looks so perfect! Have fun trying to find/make something. Hope it goes well for you. I’m looking forward to seeing your finished product!
That 40.5cm mirror I linked earlier is still at one bid $9USD and has 14 hours left to go. It will probably end up well below the $62 price of that Edmund Optics mirror. If nobody else bids on it, somebody’s gonna get it for $9USD. It can ship to Australia, and shipping is free.
Maybe for a long focal length like that, you could use a microwave dish. It seems the main problem would be getting it smooth and shiny. A simple way might be to cover it with aluminum foil.
I spent a little time yesterday making a parabolic cut-out. I'll take it with me to the shops today, on the chance that I find a bowl or something with the same contour.
And a question for the driver gurus;
If I were to piggyback 3 or 4 FET's on the same board, will the 13a have a strong enough drive signal to operate them all?
At least the write-up is already excellent, great reading, that will impress the judges as well :-) , I hope that the mirror will work out in the end. Keep going!!!
Jacks a good looking assistant but he appears to goof of as much as my two assistants. I bet if the three of them got together there'd be a bunch of trouble. Its good to see some progress on the light.
That shallow, long focal length Edmond Scientific reflector looks like it should be used in a retro configuration. The light sources they used in WWII search lights emitted in all directions.
While I was researching making parabolas, I came across the term 'spinning' a few times.
As it turns out, a liquid that is spun at a constant speed in a container forms a parabola on it's surface. The faster the rotation, the shorter the focal point.
This is what I'll be trying next, by using a low viscosity epoxy, or plaster mix.
The key seems to be keeping a consistent speed, whilst the solution sets.
Others of my group did that when I was in Germany, to use as a light gathering mirror. I think we used polyester. It should start as a liquid and not change volume too much when it hardens. I don’t recall how we silvered the surface. Evaporating aluminum on it in a vacuum probably gives the vest shine, but without a vacuum one could stick aluminum foil to the surface.
The 1964 book “Direct Use of the Sun’s Energy” by Farrington Daniels has text about making parabolas and a photo-plate showing how they made a concrete mold to form plastic parabolic mirrors. It’s out of print but cheap if you can find it. Paid $2 for my copy.
Lore from fellow radio nuts has it that the best satellite dish to use as an antenna reflector is the old “Dish 500” model; newer ones have an offset designed in for the receive head location. Parabolic reflector principles are the same for light or radio, same stuff different wavelengths.
Don’t think outside of the box, throw the box away!
