Society for Popular Astronomy

Apart from viewing the Sun in a telescope by projection, filters or the Herschel Prism, there's a fourth, slightly eccentric, way we can do it.
We can get good white light views of the Sun by pointing our 'scopes at the solar image reflected from a bucket of water. We need windless conditions to do this.
It's still necessary to have some eyepiece filtering to reduce the reflected glare. I don't know what the optical accuracy of a watery plane is but it gives nice, sharp, images. I've tried this method on the Moon too, but we don't need to filter the reflected lunar image.

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brian

What is the percentage of light visible using the bucket of water method?
I have often used the reflection of the Sun in a glass of water to see my home moving even to fairly distance traffic moving. The image on the opposite wall moves quite a bit.
At first it suprised and alarmed me how much a building moves, which is not normally detectable..

Also when the curtains are drawn a small gap is left and this gives good circular solar images on the wall using the @pinhole' effect. I haven't yet seen sunspots. Ithink they would have to be large to see them this way.

A vdery nice image appears from the the top or gap in my curtains in the north facing room. You see a complete image of the street outside and can even identify cars and see people walking past.. The whole room becomes a camera obscura. I think the images are right way up for some reason depending on where the gap in the curtains is. I am not sure about this.
The whole image is in colour.

How much do you have to filter the eyepiece using the bucket of water method?

Regards, David

I'm only guessing, David, but the percentage reflection from the surface of the water should be around 5%. As you might know, this is the amount reflected from uncoated glass ( as in the Herschel prism ).
In this case, a No.5 neutral density filter should be okay. I used a variable polariser at moderate magnification.
It would be interesting to know how accurate the surface of still water is.

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brian

There is a meniscus effect at the side of the bucket I think maybe due to viscosity?
I think the middle of a large bucket would be fairly flat.

David.

Is this for projection only?I assume I d need a proper filter to observe straight through. Very inyeresting!

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cg5

It is using the reflection of the Sun from the top surface of the water plus a dense filter. Do not try this at home if you are not sure.

I presume the same could be done using flat window glass?

When I get an image of the Sun on the wall 18feet from a glass of water it is a reflection of the Sun from the top of the water and through the glass twice. The image then is very poor but it certainly shows the builging moving when traffic goes past even distant lorries or buses.

Should say building moving.

Regards, David.

I live on a narrow boat. I ll be ick!

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cg5

Is the narrow boat a good stable platform for your scopes or are they mounted on gimbals or whatever they are called as used in helicopters for photography?

David.

I take them onto the bank.

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Do you have a problem with moisture getting in your optics?

I know someone who lives on a converted Trinity House Lightboat.
The huge lamp was removed before it was sold to him.
He probably also has a it of salty air where he lives.
It is also a photographic studio.

David.

No its not damp inside.big problem with light pollution. Garden lights at pub on all night. Farmers out all night. Now they re building lots of holiday cabins a few yards from floodbank. The joys of the countryside.

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It would be interesting to see a sunspot image on the Gallery taken through a 'scope pointed at still water.

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brian

Just what I was thinking.!

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