Trash can lid to Parabolic Mirror DIY telescope mirror Signal booster Faster 3G/4G 

You're an amazingly creative and talented guy, Dan. I've been watching you for a couple of years now, and you CONTINUE to amaze me with almost every new video!

Dan, you make some of the most interesting videos on RU-vid! Thanks for all the inspiration you give to me and lots of other people. Even if I never make a single thing you are showing, I love to know that I could. Very few people have the talent (or willpower) to show the practical uses of science and technology to the masses. Thank goodness for teachers like you that show us areas of science that we didn't even know we wanted to see.

If anyone else was wondering, the deflection of a circular *thin* membrane due to small pressure differences as a function of radius is w(r) = w_0 (1 - r^2/ R_m^2), where w is the deflection from "flat," w_0 is maximum deflection, and R_m is the outer radius of the membrane. Ref. "Introduction to Microsystem Design" WK Schomburg. This also includes formulas for figuring out w_0 from the pressure difference. So yes, *theoretically* its a perfect parabola. For larger pressure differences, thin membranes approach spherical shapes (think bubbles). For a power generation this is brilliant (cheap and adjustable). I wouldn't discard this for telescope mirrors. For example, if you can make 100 of these mirrors for the same price/time of one highly accurate mirror, you might actually get better images from the collection. There would be a host of challenges (sound, temperature variations). I bet there are some simple ways to overcome these challenges (thicker membrane, controlling pressure) without increasing the cost much.

Thanks for the video. This method was used when B.Schmidt made his corrector plates for schmidt cameras, nearly hundred years ago. Using mylar is good idea and results are interesting, esp. very short focal lenghts paraboloids.

Just a hint for people who want to make one for a good telescope: don't use it, unless you have 24/7 the same temperature in- and outside. It will slightly change it's convex shape when temperature changes. So the burnpoint calculation is for nuts... But great thing for other projects! Thanks for sharing Dan! Keep it up! ;-)

I think your videos are some of the best on youtube. I always enjoy your madness!!! thanks

technical stuff can make better things, but cheap material like this to get things done? man, you're a genius.

Amazing. It will be a nice school project I will help my daughter with, Thanks again Dan!!

The optical aberration (second surface side) and image distortion occurs on the outer most area of the vacuum lens. The F/stop aperture rings reduce the image distortion dramatically. Oversized and usage of 50% = the center section of the mirror only works My Canon 7d is dead so no video of it right now but with a secondary mirror and focuser, the image quality of the moon is good. Not a full setup yet. There are issues with the vacuum FL changes. Would need more than just a suction tube.

If you can succesfully make a telescope out of this mirror, it will be a monster

I read the comments below, Dan. You're inspiring new ways of creating energy from (what could be) waste products from the landfill or local curb. You're inspiring minds along the way. Good job, Man! :D

Cool idea Dan! Where is the easiest place to get one of these mylar blankets?

definitely one of your better diy videos that ive watched. thank you Dan Rojas

Ooooo. Thank you! Keep up the good work. I hope it works out for y'all to get a TV show. Y'all make science interesting. Thanks again, Suzie

I think I might try this with an old glass rice cooker lid. It already has a hole on the top to let the steam out and the edges are smooth. Great demonstration as always.

Dan, I just want to tell you, you are a brilliant popularizer. Thanks !

Thank you for the nice comments:-) Nice wind spinners on your channel.

Very nice! The stretching makes a real nice surface! It is not strictly necessary. The pressure will smooth the material enough. There will be some radial wrinkles, but for cooking it is more than fine. I love your videos. They are entertaining and i always learn something.

I have added "Plastidip Spray" to the interior and stretched while wet. Then you give it a spin so all the spray goes to the outer edges, draw the vacuum and it helps. Temperature changes can also make the focal length change.

Great idea!! A suggestion for hopefully an improvenment: -- After making all the above, construct a strong cylinder around the lid. -- Put water on the mylar, inside the cylinder. -- Hopefully, the weight of the water will bend the mylar into a parabole (I think!). I think that even with just this, you might have a bigger curve, hopefully a better one (!) Further: -- A clear and thick glass disc can be put inside the cylinder, with a rubber on the edge, sealing the water below. There should be a hole on the glass disc for air to escape. -- Then pushing the disc downwards, would push the water even more, and increase the curvature of the mylar. Perhaps (!!) this curvature will be better, or parabolic!! Again, you gave us a great idea!! Exactly the diy ideas for a lens I was looking for.

Dude, you're a genius! You just got a sub!! (:

Good job Dan. Sandia natl lab had done research on a thin film mirror 20yrs ago that is electrostatic. So what they did was first measure the mirror surface with a laser, then use a cathode ray to move the electrostatic film mirror surface to make it perfect.

Hi, The vacuum is not needed for flat mirrors or the drum effect but for a light gatherer, the vacuum draws the centermost surface deeper creating the curve in the mirror.

Will do, we are sunless for a few with a front. The acrylic mirrors we have are 2x as strong but this could make some tea or more? I know the big one is a monster.

Oh my god, I am SOO going to create a reflector telescope with this method! GENIUS!

Awesome work. For other applications, i like stretchy electrical tape to seal stuff airtight. Often makes the result look quite neat too. The stretchiness helps it fit around edges nicely. How fine a focus (mirror side to burn point) does vaccume accomplish? It is close to deal by chance or by laws of nature as good as it gets? Thanks!

I have a 4' diameter Andrews microwave parabolic dish. What would you suggest as a reflective coating? Aluminium foil crinkles when applied to the curved surface and disperses too much of the light.

might make sense to insert a reversed tyre valve into that vacuum hole then you can withdraw any air at will and would make for a much better seal....

what mil or thickness is this that you use here, great video thanks

Am I correct in suggesting that the greater the vacuum the shorter the focal length as long as the Mylar does not bottom out?

Excellent project .... really inexpensive and simple way to construct a sophisticated bit of kit. ....I'm going to make one. My only reservation is that the parabolic Mylar surface looks a bit vulnerable ? Would it be possible to load the trash can lid with a slow setting gel, the excess of which you could remove when you evacuate the lid/mylar space so that the mylar would settle down onto the gel surface as it attains its parabola ?

Maybe, I am testing them. Our mirrors on our site are second surface so while they produce a good image they have optical aberration for telescopes. Not a problem for solar but screws up a good image. The mylar is first surface on one side. We are making some first surface mirrors from acrylic.

Gorgeous and excellent work I wish you success

Working on a larger version

This has my head tingling about using a bicycle rim. Sure it has all them spoke holes, and would need a solid backing, but it's an option for anyone that doesn't have a garbage can lid. Love the telescope idea, but would seem a tougher mylar material would be needed for a solid focal point. On the other hand, that could be adjusted on the fly if it did change and have a sensitive vacuum gauge to dial in the parabolic aspect of it. Keep up with the kick butt vids you two!

Awesome video again! Thanks. Hey dan, if i used silicone glue to seal it, would the vacuum last longer? i'm going yo try it and use tape to hold it in place until it dries out and maybe put a tube in the back.

Nice job Dan.

That's cool. do you get sheets of mylar online? Do you have a video showing how to cook food with that? Can that itself provide heat?

If you put the tape down with a thin sliver of foil or some such over the hole, you can pull a vacuum (those little food saver/jar vaccuum pumps work pretty good), it will actually lift the tape up a bit and suck the air out from under it, and when you lift the canning seal head up the foil flaps down over the hole keepinf more air from rushing in.

The mylar stays firm over time. The vacuum does not seem to stretch it to a week point. Once the vacuum is released the mylar remains like a drum. Not sure how many years/months it will do. I have a 5 year old stretch mirror that is still firm, it is not exposed to vacuum, just stretching.

How would you get a negative pressure in space for something like this? Or are you thinking of positive pressure in front of the mirror, like a sealed telescope tube? Also, the environment in space has very large temperature changes: you have to consider the stability of the mirror surface.

This might also be useful if you do the opposite and pump air into it to make a convex surface. then you could use it as a convex mirror to see around corners, such as if your house is parked on a busy road and it's hard to see traffic coming because of walls or trees etc.

That's cool. do you get sheets of mylar online? Do you have a video showing how to cook food with that?

Great video, great technique. What did u use for the vacuum?

Great idea, excellent project, lightweight, good for cooking but not good for telescopes. Remember that a good telescope mirror will require an 1/4 lambda precision of the parabola, and anything below 1 lambda won't work even for very low magnification light bucket telescopes. And the focal length will change with the time as the vacuum degrades, so it will be close to impossible to put this in an arrangement with any type of secondary mirror.

Dan does the Mylar retain its elasticity over time or will it memory if you keep a vacuum on it after time?

Awesome!! We are so doing this! Seriously cool idea and it looked great! Thannnnnnk-you

Hi MUDDy, Seaming 6 pieces together this week with tape. looking to use 16 footers for the square design. Unless I get time to bend some wood strips. Looking for a 16 foot solar ray:-) Round would look so much better. HAPPY NEW YEAR!

Highly impressive. Thank you

Hi, I was thinking of using your idea to make a small concave/parabolic mirror in order to create a schieleren setup. Can I know how do you close the hole of the trash lid after vacuuming without outside air entering due to high pressure? the size of the mirror that we plan is from 3" to 8" of diameter. Can we control the focal length?

That's brilliant! I am going to have to try that.

interesting...I hope you make a video explaining this in more detail sometime. I LOVE your channel man.

Really smart never used mylar sheet before. Will make a nice solar cooker. What is the specifications of the mylar sheet?

Love your videos! If you could, could make a video demonstrating how well this design cooks food or boils water? I think some of us would be interested in seeing that. Thank you again and keep on making great videos! :D

Dan, how well does Mylar reflect UV light. I am working on my exposure box and mirrors are ok but but low uv reflectivity due to the glass. Is Mylar better than a mirror to reflect UV light?

at first I thought there was a washing machine running in the background :D that's really a neat method to make a parabolic mirror!

I love your instructional videos! Very helpful. I'm wondering if this system would work for making large rectangular mirrors for an art installation. Provided the mylar is taught, does the surface provide a clear reflection?

Did you try looking at the parabolic mirror with an eyepiece to see if it is accurate enough to use as a telescope mirror?

Thanks Dan! Looking forward to it!

Love the video. But question, will this work for the base mirror of a telescope ?

If I wanted a small pocket sized parabolic mirror you think this same thing would work with a pickle jar lid?

To create a vacuum could you just push on the drum face while air hole is open, seal the hole with the tape tab and then stop pushing on? It seems like it would be easier to do than using a pump and tubing. I don't know if the mylar could take the abuse, though.

you're my man guy, thanks for the idea

I have deleted most of the optical aberrations causing image distortion. I will have a video soon explaining the simple process. Very effective for low cost reflectors as they can be designed very large and any surface area loss for optical corrections is not an issue as compared to a real mirror that each sq cm of surface costs lots of money.

Do you think if you put expanding foam (the stuff you fill big gaps with that goes hard), you wouldn't need to worry about keeping the vacuum. Or what about sticking the edge of a round piece of mylar to a flat surface and inflating it, and then put expanding foam on top.

Dumb question: Why do you need the vaccum? Does it make the mylar tighter/more reflective. Thank you, Suzie

Another awesome project I can't wait to put on my list lol. One of these days.

The image quality is good from the center 50% of the mirror, the outer 50% screws it up. For solar cooking it does not matter as light is light so long as it covers the cooking vessel but, I have shrouded part of the mirror and it helps dramatically while also reducing the collection area. Since we are using cheap materials, I am thinking a 40" mirror could make a working 20" mirror 50" = 25" and so on. CPF bulb images very good.

I didn't had any Mylar lying around in my house so I used the inside of a bag of chips, which seems to work as well as a mirror (haven't tried making a parabolic mirror using a vaccum though). However it did not seem as clear as the Mylar, and its size is much smaller.

Here's an idea! Try bridging a speaker magnet from the edge at four points, then silicone glue a speaker coil to the center of of the mylar. I wonder how that would sound? I'd use it with my piano sound board and strings that I have hanging with homemade pickup coils. I hammer, scratch and pluck at the strings for a really freaky sound. I'll bet the sound and feedback ability would be just incredible. Peace :)

I wonder if you could use a hoop made of PVC backed by a wood disk to create a larger mirror?

So is the vacuum just to make it more parabolic? How do you think it would do without the vacuum?

Absolutely Brilliant

Attach tubing (mostly just to get distance to the mylar), insert a coil, then you can control the temperature on the inside electrically, within reasonable margins, of course, without moving parts or pumps. All you need is initial vacuum to be in range, close the valve, start and stop heating as necessary.

Is we are able to get parabolic mirror will the reflectiveness be enough for astronomical use

MORE TELESCOPE MIRROR PLEASE... can you do a complete one ? lol your Genius ...

Did you come up with a way of having these hold their parabolic shape permanently in this handy Mylar + bin lid configuration? Maybe pressurise from the outside and introduce some resin through the hole in the back and swirl that around to coat the inner surface and set in that distorted shape? Or use the vacuum as shown here and then spread resin on the shiny concave face?

It looked like a forming black hole distorting space-time when you pulled the vacuum!

excellent idea and working proof!

Thank you:-)

Could you use heat to create the vacuum? heat it under a burner and then seal the hole and as it cools watch is tighten?

Can you use this technique to throw fiberglass resin on that Parabolic shape

thanks for the reply and one more thing will it be really reflective enough to use as a primary mirror of a telescope

Can this be used to melt snow on driveway during winter as the sun rays does not fall our side. The sun rays are on the opposite side of our house?

After you draw a vacuum how do maintain it during that brief moment your resealing the hole with tape without losing the vacuum? Seems to me you'd lose the vacuum before you could get the tape back over the hole . . .

rescued a couple satellite dishes from the trash a while back with no idea what to use them for ...i wonder if i can use the for this?

I liked it. What about a one way valve in the hole ? Be good if you could press down on the handle, to draw out air.

Oh that’s awesome, thanks for showing me how to do that.

you are one cool cat! thank you for sharing

is that the only way? It is kind of already assembled I have to constantly pull the vacuum.

The silicone can get messy with the stretching. If it gets on the first surface side in the form of a smear, it will not come off. If you do it, just light coat. I think it will work. The design is for human powered vacuum suction. If you use silicone do not do that for a few days. Vapors are :-0 Use a shopvac or other pump.

Great vid!

where did you know from, the vacuum is creating a parabolic surface? (not spheric or anything else) Has someone a link to the physics? Thank you!

Slick! Thanks for sharing

THANK YOU VERY, VERY MUCH!!!

Pour enough resin in to coat the inside, then draw the vacuum. It should stick to the Mylar and maintain its shape when depressurized.

Is this a parabola or a catenary shape? In space you are going to have to draw a better vacuum better than that of space. I once inquired into just venting a mass spectrometer to space and I found out that the vacuum of space is rather "dirty".

There are youtube videos on how to build a one way check valve with pvc or abs fittings. You could use one of those to pull your vacumn through

The profile of that mirror isn't parabolic; it is a segment of a sphere. As air pressure pushes in on it, the mylar will behave like a bubble membrane. Since air pressure pushes perpendicular to the surface at all points, it cannot form a parabola, only a sphere. If all the air pressure were parallel to the axis, then you would get a parabola. Because it isn't a parabola, the light focus will have some spherical aberation to it, making it unsuitable for precision optics. But it is definitely more than good enough for solar concentration.

I got my vacuum to hold for about 30 minutes what have yall done to elongate that time?