Preparations

I prepared rather early and seek where to get a sun filter for the telescope and also the too falous « special eclipse glasses ».

Since Spring, I knew that my favorite science magazine would enclose a pair in its August issue. But that would not be enough for the whole family. Moreover, a bad news could happen and the awaited object not be available just in time.

After a visit in some shops in Nantes where I found just nothing, I choosed the Maison de l'astronomie (the Astronomy House). The best quality/price ratio was to a black polymer film. I also decided to buy ten glasses cut in the same metal.

Commande

But ten pairs, that was to much: it was a good occasion to make gifts to some friends. And they were far better than mylar glasses.

A sympathetic gift, ain't it?

 

I now had to find a secure way to place the filter in front of the telescope mouth. No side light should be able to penetrate the tube. In fact, a single ray of non-filtered light would have been very dangerous. Concentrated by the telescope mirror and the eyepiece as well, sunlight would with no doubt cause irreversible retina burns.

The telescop I am using ships with a stopper. In the center of the stopper is openened a hole with a second stopper. This works as a reducer for observation of the Sun with a special filter before the eyepiece. I cut a piece of polymer film that stuck behind the reducer hole. It immediately allowed me to observe some sunspots.

But proceeding that way reduces the effective telescope aperture and thus its performances. It was necessary to realise a full aperture filter.

For this purpose I used a black plastic flower basket which diameter slightly exceeded the telescope tube diameter. I removed the bottom of the basket. I then cut it by half so that I obtained two truncated cones that perfectly fit one into another. Over then narrowest, I tightened a polymer film disc and taped it before placing the larger one over the construction. Sandwithed between the two plastic circles, the film was strongly fixed. Inside this new accessory, I stuck this foam usually used to insulate the windows so that it was necessary to slightly force to place the filter on the telescope's mouth.

The result exceeced whatever I could expect.

As it was remaining a large amount of polymer film, I also built a filter for my 600mm telephoto and equipped my binoculars.