Construction of the Galileo’s telescope with recycled materials (a DIY).
Every amateur astronomer remains amazed at how Galileo, with his rudimentary telescope, has been able to make so many discoveries, so the curiosity to look into the eyepiece of the first telescope of the story is great. On Galileo’s telescope, on how it was built and how to build a copy, you can find many articles. On the site of the museum in Florence for example it is reported the optical design and on the Sidereus Nuncius (alternatively, also here) there is of course the original scheme of Galileo. The solution presented here is an educational alternative and also (very) economic, to get an instrument, in principle “similar” to the Galilean telescope.
Rummaging through my recovery of lenses and camera lenses I did not have a plano-convex lens of 50mm in diameter and one meter focal length (so it was probably that of Galilei) So I thought it might be possible to use an additional macro lens or a simple eyeglasses lens of one diopter (+1) that is one meter focal length indeed.
Both the eyeglasses lens and the additional lens are meniscus, the main difference with the plano-convex lenses is that the last have a more pronounced spherical aberration. However the main purpose was to respect – at least – the focal lenses of the Galileo telescope.
To stay on the field with the material that anyone can have in the house, as primary lens then I used the lens of an eyeglasses. For the eyepiece was needed a plano–concave short focal length (about 5 cm). Fortunately among various recoveries I had a couple that could be fine. From an old video surveillance camera I removed all lenses and I used the barrel as accommodation for the “eyepiece” lens, that plano-convex. The first tests – by mounting these two lenses on a cardboard tube and framing the Moon – indicated that the way was the right one.
Some lenses from “scrap” photography, at the top, to the right the plano-concave lens for the eyepiece and the primary lens (objective) from the +1 eyeglasses, it is also recoverable from some eyeglasses sold in any hardware store for few money.
Using the hacksaw (piercing saw) were made two wooden disks to accommodate the lens glasses:
Construction of the support for the lens and tube section of 60 mm for the primary lens.
Holes obtained with hacksaw.
For the body of the telescope the logical choice falls on plastic pipes for plumbing. A tube of 50 mm for the main body, a tube of 60 mm to accommodate the objective lens and a tube of 40 mm for the focuser. Fortunately the barrel of the old videocamera sit almost perfectly in the secondary pipe. To accommodate the various pipes together, they were wrapped by strips of fabric like velvet.
Even if the focal length of the main lens is one meter in the end the whole length of the telescope is about 90 cm because the secondary lens being a negative (plane-concave) shortens the total focal.
After blackened inside the tubes and any other parts with spray paint, was prepared the primary lens, with the possibility to remove the lens and replace it if necessary in the future.
Support for the main objective almost finished. The two disks glued between two thicknesses allow the removal of the lens, but when the support is housed in the tube the lens can not get out.
Mounting of the eyepiece in the tube.
For a finishing touch there are two alternatives: painting or coating with some material. The Galileo’s telescopes were covered with leather, my model is coated with a plastic material found in a shop of fabric scraps, It is like synthetic leather, very thin but very vaguely reminiscent of the leather.
Coating the pipes was the much longer job, in total to build the Galileo’s telescope took about six intense hours.
The total cost of this enterprise can vary depending on what you can recover, but no more than 20 to 30 euro/pound/bucks.
Being able to play the original decorations of the most famous telescope in history (the second in the bottom of the picture above) it is only a work for artists or professionals. Personally I opted for the simple golden profiles (dc-fix), one for each original decoration, moreover I added a kind of plate to make it clear now to everyone that this is not a whatsoever refractor.
As housing for storage when not in use, I used a cardboard tube covered with pages from the Sidereus Nuncius , an idea that I found online, very beautiful and aesthetically pleasing.
My daughter watching the Sun with the projection method, the sunspots are clearly visible.
The setting Moon, on the left a simulation of what we seen through the telescope, the image is very bright and sharp, affected only by a light chromatic aberration on the edge. Photographing the Moon through the telescope is an hard job, on the right an attempt to photograph it, hope to do better in the next time.
This above was made a couple of day after…
Notice that through the eyepiece is visible only a part of the Moon, but moving your eyeball around you can see the whole Moon, so Galileo saw for the first time our satellite more than 400 years ago.
If you are interest into a true whole woodden copy go to my friend Antonio