Transit : Technology of the observation

While observing any phenomenon in the Sun, it is necessary to pay attention to security, because by a direct look in the Sun without a protective filter you can destroy your sight. That is why it is needed to get the right tools, which can easily be prepared even at home.

Observation by the naked eye

Venus' disc has luckily a relatively big diameter, with regard to the Sun it is about 1/32. So, this phenomenon is ideal for observation without use of telescope or another tool, but you must have a reliable filter. Do not use anything which is not tested and recomended by a specialist! For example, many people use for observation of the Sun discs from diskettes and that sort of thing. These tools filter the sunlight in that way, that your eyes do not hurt, however, at the same time they do not filter that UV light component, which damages the sight irrecoverably. The best thing to do is to get welding glass no. 12-15. You choose the concrete number of the filter accordingly to the cloud amount. The ideal tool are protective glasses, as well, which are designated for observation of the Sun eclipse. Nevertheless, if there is none of these tools available, it is possible to use, for example, a thickly overexposed film.

observation by welding glass

Observation by a telescope

While observing by a telescope it is always necessary to use a filter inserted before the telescope's objective, otherwise there is a danger that you lose your sight forever! If you filtered just the light emiting from the ocular, the filter would not need to resist the energy converted into heat , it would be damaged and you could lose your sight.

In the case of observing the Sun in a refractor, it means a telescope comprised of lenses, you must have a good filter, which will reduce the sunshine on about 1/100 000. These filters, however, tend to be quite expensive and what is more, all their faults are multiplied in the telescope, so this method is not very favourite for amateurs. A suitable tool for the transit's observation are simple field-glasses, but again, there must be a suitable filter on both objectives.

observation by telescope

Observation by projetion

This method is quite favourite in observatories and other places, where there are accomplished large-scale observations for larger groups of people. A great advantage of this method is, first of all, its safety (because you do not look right into the telescope) and also the fact that more people can look at the same moment. This principle is based on the fact that before the telescope's ocular (this time without filter) there is placed a "projection screen" , to put it differently, a suitable flat tool, on which the sunshine will project. The simplest way to do it is to place a normal cardboard before the telescope, but again it is necessary to follow particular safety rules, because if you placed this cardboard too close to the ocular, it could catch fire. The projection surface should be located in the shade, so that the picture is the most contrasting.

observation by projection