Alright, so I just lost an auction for a large satellite dish I was going to convert into a parabolic mirror, and there probably aren't going to be any going up on auction for a while.
Does /diy/ know any techniques for making one other than making a satellite dish shiny and chrome?
Pic unrelated, and probably not edible gummy candy.
>>917505
Is revolving a big drum of fluid out of the question?
>>917521
If I can find a drum I don't see why I can't revolve it.
Like, I have eclectic drills and stuff, and other things that spin.
>>917505
You could do it this way
https://youtu.be/5rYr1Yrqwrk
>>917505
You mean a large one like this,
http://www.ebay.com/itm/240cm-8ft-C-Ku-Band-Prime-Focus-Mesh-Satellite-Dish-Package-/331369082628
Or a smaller one like this,
http://www.ebay.com/itm/36-90cm-Satellite-FTA-Dish-with-4-Degree-Kit-w-2-LNBFs-/121557701508
How large, anon?
Some people make woks and paella pans out of the ends of large metal tanks. The kind that have a domed head would work. Another method is to make a flat Solar Death Ray (SDR). There's quite a few SDRs online, just google them. They are essentially the Fresnel equivalent of a parabolic mirror.
How big are you talking about? Parabolic and ellipsoidal reflectors are really easy to lay out with a piece of string, the only hard part is maintaining precision as you fabricate it. Size will determine what method and materials are viable, so we need to know that.
https://www.google.com/?gws_rd=ssl#q=homemade+parabolic+reflector&safe=off
>>917668
I was going to post some of the links in this search.
How big and smooth/precise does it need to be? Edmunds Scientific sells very smooth parabolic mirrors up to 24" across.
There are umbrella reflectors for grow ops and the like, but I'm sure they're pretty sloppy.
>>917668
>the only hard part is maintaining precision as you fabricate it.
>How big and smooth/precise does it need to be?
This. Do you need optical-grade consistency, or is some amount of aberration acceptable? Is this just a collector dish for power, or is it for a telescope?
>>917720
>but I'm sure they're pretty sloppy
It depends really on what you want to use it for. If you're looking to melt some steel, then you are correct. If you want to just cook some lunch in a pot, it works just dandy.
OP here, should have given more specifications.
I need the mirror to track the sun, and get a nice steady beam going through a prism, because I want a garden with a permanent unmoving rainbow on it during the day for scientific purposes.
I suppose X and Y motors with a big reflector facing the sun bouncing light into a smaller reflector which shines light through a hole in the big reflector would be what I do to get the beam, but I don't know how much accuracy I need until I know my method for getting that angle-changing beam to point into the prism at a single angle.
As for size, I'd probably want at least a metre in diametre.
>>917530
Heat the water, then put molten wax on top and leave to set. Then you have a mother mould to make your plaster dish.
I just bought a 1,5m in diameter one. It even has a tracking motor. I'll have to somehow figure out how to track something with it. This electronics shit is beyond me asd you can't just weld electronics and then grind and reweld if you fuck up :)
The tracking motor s an old nokia from the nineties, it supposedly works . If anyone understands even slightrly how these actually get the signal to move then please let me know! I'll dig out the model number as soon as I? go out.
The dish itself is aluminium so I ight try just to polish it and if it works then I might do a small happydance!
>>919086
Oh, and it was for a total prize of 10€
>>917505
Youtube-Greenpower science has a lovely method.
Take a trash can lid, wrap the edge in duct tape, put silicone on that, and gingerly affix mylar to it. Add a vacuum fitting to the lid and pull a very slight vacuum. Magic parabolic reflector.
If you need one bigger than the lid, you can scale it up with wood. The limitation is the width of mylar you can get.
