| Author | Message | ||
     Stuart Seed |
Hi, Great site! I was wondering if anyone could point me in the right place for a plan to build a Solarscope, so that my class can build a few prior to the transit of Venus on the 8th June. Ideally simialar to the design on www.solarscope.org Thanks Stuart | ||
| Simon Quellen Field (Sfield) |
Any telescope can project an image of the sun. Just place a piece of white paper a foot or so from the eyepiece. Use the shadow of the telescope to aim, don't look through the eyepiece. You don't even need a telescope -- a pin hole in a piece of cardboard will work. | ||
| Stuart Seed |
I would not recommend that to anyone with a telescope. Without a solar filter on the FRONT of the scope you can ruin a telescope very quickly. I was looking for a plan similar to the ones on that site, any ideas? Thanks for the feedback though. Stuart | ||
| Simon Quellen Field (Sfield) |
Many of us with telescopes do this all the time. Many telescopes come with attachable screens for solar eyepiece projection. Many telescopes also come with eyepiece solar filters. What damage are you expecting? I would expect it would take a pretty big mirror to concentrate enough solar power at the eyepiece to overheat the metal of the eyepiece or focuser. In fact, the solarscope web page you point to shows a small telescope aimed at a mirror that projects the image onto the top of the box. This has the drawback of projecting the image onto the back of the telescope itself, so that often the telescope blocks the view. Simply eliminating the mirror and letting the image be projected onto a screen directly lets you see it with your back to the sun, eliminating the squinting you get from the design shown, where the kids faces are in the sun. Using a simple telescope and paper screen, it is also easier to adjust the size of the resulting image by moving the screen back. More people can see it at once, also. Lastly, the solarscope claims "image quality better than one wavelength", while an inexpensive telescope can be 10 times better than that. Whether the extra optical precision is worth anything looking at the sun through a warm atmosphere is questionable, however, and a good scope may be overkill. Lastly, don't forget that a pinhole in a big cardboard box also allows you to see sunspots, eclipses, and the Venus transit. And it's cheaper ;-) | ||
| Stuart Seed |
OK I`ll give the pinhole idea a try. I suspect that a cheap refractor may be ok, (after all I did the same thing as a kid and was allowed out of lessons for ages as we observed sunspots, OK I knew it was dust on the lens but it was sunny  ) for the eyepiece projection method, however Ill not be giving it a try with my 8" SCT. You would be concentrating a large amount of energy into a relatively small sealed tube, not to be recommended with several thousand dollars of telescope. Especially as solar film is only a few dollars. I was interested in the Solarscope design as Ive seen them in use and they work really really well. Stuart | ||
| Simon Quellen Field (Sfield) |
The trick with the pinhole is to let your eyes adapt to the dark. The resolution depends on the size of the pinhole, so the image should be a few thousand times the diameter of the pinhole. This means it will be faint (several million times fainter than the sun seen through the pinhole. A large refrigerator box was used for the one we had when I was a kid, and a blanket was draped over where you stuck your head in, much like old-time photographers used. Using a lens, or a cheap toy telescope or half of a pair of toy binoculars would allow a group to see it without the blanket. Add a mirror and you have a solarscope. |
