John builds a Galileo telescope look-alike

John builds a Galileo telescope look-alike

Published by Nick Lomb on April 25, 2009 No Comments

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Dolores holds the Galileo telescope look-alike, picture courtesy John Flavin

Early on this year – the International Year of Astronomy – the thought crossed my mind that it would be a nice thing to have a Galileo era telescope. Browsing through the Internet, I soon discovered that a lot of other people must have had the same idea, as there were a few sites offering Galileo telescopes for sale. Pursuing this matter further, I came across one interesting site – that of the Institute and Museum of the History of Science in Florence (Galileo’s home town, one might say). Only two of Galileo’s telescopes survive, both of which are in this Florence museum, and the museum site gives details of their construction.

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Close-up of the eyepiece end of the Galileo telescope look-alike, picture courtesy John Flavin

After reading up on both the commercially available ‘replicas’ and the details provided by the museum site, I decided to have a try at making my own Galileo era telescope. The photographs shown here are the result – what I might call a Galileo era look-alike telescope. It seems that the first telescopes had tubes made of metal or wood, with cardboard (for lightness and strength) becoming common later. The tubes were covered with leather or other fabric, which was often finely decorated.

In making my own ‘replica’, I have used some very non-Galileo era materials: The tube is PVC 42mm outside diameter, as used by plumbers, covered by Nylex ‘Cover-it’, a sticky-backed material used a lot on bench tops and obtainable from Big W. The drawtube holding the eyepiece is a cardboard tube, which was left over from a roll of ‘Glad-wrap’, also covered with the same sticky-backed material as used on the main tube. However, I had to use several layers to fatten it up to a nice sliding fit inside the main tube.

The pictures I have seen of the first telescopes show the tubes to be nicely decorated – in particular the one in the Florence museum which I have tried to copy. The red bands on the main tube and around the eyepiece were cut from glossy photographic paper, which had some ‘red’ printed on it, and glued onto the tube. As for the gold decorative shapes, these are stock self-sticking items obtainable from craft shops.
As for the optics, the objective is a 42mm (stopped down to 30mm) 800mm focal length spectacle lens. This fits nicely inside a PVC coupling for 42mm tubing, and is held in place by a ring cut from 10mm thick MDF material – the retaining ring also stops down the lens. The eyepiece is a lens I had lying around, which has a focal length of about 30mm. (It is not a negative lens, as I believe Galileo used.)

What can I see? Well, I believe I have a wider field of view than Galileo had, because of the eye lens – the craters on the moon are visible. Jupiter does have four star-like things in attendance and the crescent phase of Venus is discernable. As for Saturn, this object is not a good test because the rings are edge on right now. How about sunspots? – I’m going to leave this one for Harry. For about $45.00, I feel I’ve got a reasonably good Galileo era look-alike telescope.

John Flavin, amateur astronomer and member of the Hawkesbury Historical Society

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