Eclipse viewing

Leifer · May 22, 2012

I witnessed the May 20th 2012 eclipse through an unconventional manner.....while this method is known, it's not reported on, all that much.
Suggestions are "welding glasses #14, camera filters, and pinhole viewing.
Here's what we did......super easy.

I learned about it when in middle school during another eclipse. Actually, I discovered it myself, playing around with a mirror in science class.

Leifer · May 22, 2012

I wonder if the "Transit of Venus" on June 5th 2012, will be viewable this way ?
Because Venus is such a small object.
??

Mick West · May 22, 2012

That's very cool, like a giant camera obscura. I'd not heard of this method.

I think the blurring will be too much for Venus. If you can't see sunspots, then you are unlikely to see Venus. I'm surprised it's as well defined as it is. You could progressively cover the mirror to get the image more in focus (but dimmer)

I use Ye Olde focusing with a spyglass type thing (Binoculars), like this guy:

Leifer · May 22, 2012

Yes....the image of the sun was a bit blurred....not sure the transit of Venus would be in focus....as it's a small dot, across the sun....
I do have some "first surface mirrors" but not sure that would make a difference.

Actually it was a lot of fun....word got out that there was a sheet with the eclipse on it....and eventually people started showing up, "we heard about the eclipse on a sheet, so we came by to see it.".....Ojai, CA

Here's my girlfriend, along with some tree-filtered bookeh of the eclipse.

Leifer · May 22, 2012

hmmmm....I will try various methods, to project the sun on a very large surface, via the mirror method.
There's some optics I need to research.

http://astro.ukho.gov.uk/old/Helston/VIEWING_METHODS.html

When we were in Curaçao we had a 7 cm diameter image on a screen which was in full sun light. The screen was approximately 5 metres away from the mirror. If we moved the mirror further away the image just faded away. The Head of Science at the International School of Curaçao, succeeded in making an image with a 20 cm diameter. He did this by having the mirror in the sun, but projecting the image into a shaded classroom. This improved the quality of the image, as most of the light beam was in the shade. This improved the contrast between the image and the background.

When using a normal mirror, you get a slight double image. This is caused by the sun reflecting off the front of the glass, as well as the silvered backing and can be prevented by using a front silvered mirror. This method is suitable for group use, especially young children. It is extremely safe, and the image can be drawn around leaving a permanent reminder of the eclipse. Professor John Parkinson is continuing to develop this technique. Full construction details will be available through the ASE & Sheffield Hallam University.

I will try my "first image mirror" tomorrow. This means the mirror portion of the glass is on the outside surface, not behind a thickness of glass.....like that used inside an SLR's camera. I picked up 3 of these babies years ago, at my local surplus shop.....6x6 inches.
I guess it's possible to capture a smaller, more detailed image....then displaying it larger via a digital projector. But I tend to like the idea of a "non-digital" projection.

Mick West · May 22, 2012

The optics are rendered rather non-intuitive by the sun being incredibly large and incredibly far away. It make it difficult to draw diagrams of what is going on.

Leifer · May 23, 2012

side note.....
The use of sunlight or "available light" in art is very interesting.
James Turrell ....love his art. But you really need to see his work, in person.

Watch these two....

Leifer · May 23, 2012

I did some trials. No math is used....just trial and error.
I glued a 6x6inch "first surface mirror" with epoxy to a 10-24 threaded phenolic (plastic) stand-off. This allowed me to mount it to my tripod.

Then I did some tests.
As-is....the 6 inch square mirror only produced (focused) a round sun shape at about a 100 yard mark, onto a neighbor's wall. It was bright, but not well focused. I think if I could have projected it further away....it would be more focused, but dimmer.
I then cut a hole in a piece of cardboard about 2 inches round, and placed that over the mirror. This made the mirror much smaller.
I got a smaller, more focused image, but also less bright........and was able to project it at a lesser distance.

Though the uncovered 6 inch square mirror was brighter and larger, I was limited to how far I could project it and test it for focus. The farther away, the more focused, but also less bright.
My neighbors' walls were my canvas....and surly they were wondering "wtf ?"

Leifer · May 23, 2012

Here's some photo results....

2 inch mirror hole.

at 25 yards......

At 50 yards...(on a tan/brown wall)

Leifer · May 23, 2012

I have access to some very expensive "rear projection" screen paint ($200 quart). I could coat a piece of clear plastic (lexan, plexiglass) with it, and it would make a wonderful screen for the projection.
I'm getting really nerdy-obsessive about this....but heck, you only live once.

Mick West · May 23, 2012

Well, the transit of Venus will not happen again for another 105 years. It's not often that there really are once-in-a-lifetime opportunities.

I don't think the mirror method will cut it though. You would need to have a very small surface silvered mirror, and project it through a hole into a large dark room.

Leifer · May 23, 2012

I'm searching for a method to allow the mirror to track the sun's movement....a motor and sensor.....to keep the image in one stable area as the earth rotates. I believe some newer telescopes do this, but I am in a DIY mode at present.
This would make the image able to peek through a hole, in a darkened room, as you suggested...to view. depends on the focus accuracy of course.

Leifer · May 29, 2012

Like these maybe ?? dual axis solar tracker
...not sure of their accuracy....may not be too "precise" though.

http://wn.com/Simple_DIY_Solar_Tracker

There are more common uses of these "solar robots", like for ideal positioning of solar-cell panels, and parabolic mirrors aimed to heat/boil water.
http://www.ffwdm.com/solar/solar-index.htm (single axis)

The mirrors used here are flat, but when used in total, all the mirrors combined result in a parabolic effect.
(check @2:00 of the video....interesting)

There is also one near the California/Nevada desert.

Leifer · May 30, 2012

Another method.....

This author has some very entertaining videos....watch some.
...like this one... http://www.youtube.com/watch?v=oNRDvDIqD1M

Leifer · Jun 6, 2012

I did not witness the Transit of Venus,,,,but here's a NASA video...

Leifer · Jun 7, 2012

[video]http://www.colbertnation.com/the-colbert-report-videos/414929/june-06-2012/transit-of-venus---mars-reality-show-pitch?xrs=synd_twtbtn&xrs=eml_col[/video]

Eclipse viewing

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