As many of you know, I'm holding an eclipse party on the 19th of this month, to watch the annular eclipse that will be occurring in my "neck of the woods". One of the things I'm planning on doing is constructing a "pinhole projector", to display an image of the eclipse in real time, since I don't have such fancy equipment as solar telescopes or even welding goggles (not a good idea to use anyway, since that's not what they're designed for). In doing some research on the optimal dimensions for the projector, I stopped at the proper Wiki entry to find out things such as pinhole diameter and focal length. I bring this up because while I was on the wiki page, I ran across this statement:

Quote from: WikipediaNASA (via the NASA Institute for Advanced Concepts) has funded initial research into the New Worlds Mission project, which proposes to use a pinhole camera with a diameter of 10 m and focus length of 200,000 km to image earth sized planets in other star systems.

And I began to wonder... In what universe is 10 meters considered a pinhole?!?!?! And where the heck are they going to set something like that up??? Isn't 200 thousand kilometers just over half the distance to the moon?   o.O

It's entirely up to you Dave, but I think you may want to scale that down some. 

Found this Dave if it's of any use.


http://www.kodak.com/ek/US/en/Pinhole_Camera.htm

Where are you going to find a pin to make a 10 meter hole , that's nuts 

But I found a page that tells you how to make a Pinhole Projector for such occasions.

http://www.exploratorium.edu/eclipse/how.html

One of the best 'kitchen science' ways of observing an eclispe (especially if annular) is with a collinder and a bucket of water.

The bucket of water gives you a viewing area and the collinder has multiple 'pin-hole' cameras giving multiple images on the water's surface. The collinder MUST have round holes of equal-ish diameter.

A pin hole camera, with a white sheet of paper to view the image, works well too.

I've been performing some experiments in the back yard, and I'm finding that imaging the sun projector-style through a tiny hole simply isn't bright enough, nor is the resulting image all that large (less than a half inch at six feet), so on to plan B, which is to take a small, weak magnifying glass and use it as the objective lens of the projector. The idea isn't to focus the light into a point, but to create an image of the sun that's the same diameter of the glass, which should (presumably) put the resulting image at best focus. The results are quite satisfying; the focal length has dropped from six feet to less than 2, and the image has increased from a half inch to two inches. It's a bright and clear enough image to see sunspots (at least I THINK that's what I'm seeing), so I'm happy with it. I just need to build the box to hold it, and contrive a way to aim the device. I may also ramp up the size of the magnifying glass in order to get a bigger, brighter picture.

Glad to hear you got a working prototype be careful with that magnifying glass you would not want to start any forest fires 

I got the projector completed, and took some pictures of it:

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Looks great Dave  , nicely done 

Indeed, very impressive and tidy 

Came out great, WTG. 

Well, it LOOKS pretty. As to how it's going to work? That remains to be seen. I expect a certain amount of blurring, since the sharpest image is also the one that will ignite the paper, but I'm hoping it will not be so blurry as to be useless. I really can't test that till the eclipse begins, and that's just exactly too late to do anything about it.

Well you can pat yourself on the back for its appearance

If nothing else its plan B, when we had an eclipse here, few years back now, I had a pair of free very dark glasses from a news paper, or was it a shop  hmm! can't remember but they worked ok.

For me the strangest part was the almost complete darkness in the daytime, something you could miss if you just look at the eclipse its self, don't know if it gets that dark with an annular eclipse?   

Yeah I used dark glasses and a piece of cardboard with a hole in it plus piece of paper.

Did you notice it all went quiet ?  All the birds stopped chirping.

Quote from: Freddy on May 10, 2012, 19:26:23 PM
Did you notice it all went quiet ?  All the birds stopped chirping.

Yes indeed I did, its was a very strange event, dark and quiet in the middle of the day.