Monday, May 28, 2012

A Step by Step Guide to Making a Binocular Projection System for Viewing the Transit of Venus

What you will need for making a binocular projection system. Binoculars (of course), a tripod, a binocular tripod adapter (or, if you have an older model of binoculars, lots of gaffer tape), some sturdy cardboard, pencil, scissors, aluminium foil and gaffer tape. Using your binoculars as a template, draw circles on the cardboard that forms the sun shield where the binocular lenses will fit. The sun-shield will stop the projected image of the Sun from being washed out.
Carefully cut our the holes so your cardboard will fit over the lensesNow set up the tripod and attach the adaptor. These adaptors can be bought at all good optical stores.
Attach the binoculars to the adaptor. If your binoculars do not have an adaptor attachment, lashings of gaffer tape work as well.Carefully slide the cardboard sun shield over the binoculars (yes, I used old pizza boxes, they work and are cheap). The carefully put the aluminium foil over one of the lenses (so that you don't have overlapping images.
You may need to stabilise the sun-shield with a piece of tape. Remember to NEVER look through the eyepiece of the binoculars (or any projection system). To align this set-up so the sun shines through the lens, move the system so that the shadow of the rig is minimised as  described for the telescope here.And now you are all ready to go. Here I am projecting on to a wall, but you may want to use a stick attaching a piece of card to the binoculars, as walls and such will often be at an inconvenient angle so the image of the Sun is distorted (as in the example above).

And now you have a low cost set-up for observing the transit of Venus (now just over a week away on June 6). You can photograph the projected image with a simple digital camera (see here for an example). Getting the imaged focussed may be a problem. I draw a small cross in pencil on the projection surface so the digital camera has something to focus on.

Do practise setting up and imaging before the day of the transit, so you are familiar with the set-up.

Always be careful to avoid looking at the sun directly and NEVER look through the eyepiece (this can cause some frustration as you try and line the binoculars up using just the shape of the shadow as described here, but the frustration of permanent eye damage is worse). If you have small children with you, be very alert that they don't try an look into the projecting eyepiece.

Now, get ready to enjoy the transit!


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