Transit of Venus

as viewed by pinhole telescope

Don't look through a normal telescope! I take no responsibility whatever for anyone who does!

pinhole telescopeIn the picture you can see the Dace Pinhole Telescope in action.

On the morning of June 8 2004, from 05:13 to 11:26 UT (06:13 to 12:26 British Summer Time) the transit of Venus will be visible anywhere in the world that there is clear sunshine.

This is an unusual celestial event, in that it has happened only six times since the invention of the telescope, will happen again in 2012, and then not again within our lifetimes. The transit of Venus is when the planet Venus crosses the face of the sun.

Some of you will remember the recent lunar eclipse. At the very least, these things give a momentary sense of scale, also a sense of wonder.

The transit of Venus will be less dramatic than the eclipse, and you will need special apparatus to see it. Some say it will be visible to the naked eye using a suitable filter, but if you do this, beware of the risk of eye damage. Certainly you should not attempt to view the sun through binoculars or a telescope. The safe way is to project an image of the sun through a half-binocular onto a piece of card. You may find you will need to use grey card, because white might be too bright to look at. To line up the binocular or telescope, arrange it so as to minimise its shadow.

If the sun shines into your window, you could close the curtains around a piece of card with a pinhole in it and project the image from the pinhole onto a piece of white paper or card, placed at least five feet away.

I am hoping to view the transit of Venus using a pinhole telescope. This truimph of British engineering consists of a cardboard tube (about 5 feet long for an image of the sun about the size of a penny; bigger would be better). One end is covered with black paper with a small hole in it made with a compasses needle. The other end is covered with white card, onto which the image of the sun is projected. To view the white card, a small hole is cut in the side of the tube into which a viewing tube can be inserted. The viewing tube is not essential but cuts out extraneous light.To line up the pinhole telescope, arrange it so as to minimise its shadow. It may not look very high-tech, but I hope it will work. Venus should look like a small dark speck against the bright circle of the sun.

You can find lots of stuff about the transit of Venus by typing "transit of Venus" into Google.

Well, my pinhole telescope worked, although at first Venus was a bit hard to make out. It appeared as a tiny fuzzy dot. Later it became easier to see.

Someone asked if there were any mirrors in the telescope. There aren't, but I realise now that I could have doubled the path length (and hence the magnification) by putting a mirror inside.

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