For the same 28 Sgr/Titan event several other video recordings were made by professional astronomers and amateurs alike. One of them, Jean Bourgeois, used a Philips module at a 25 m Newton telescope at Pic du Midi. The sensitivity was such that Titan was not visible during the occultation of the star. Since no point like reference object was available in the field of view I had to use Saturn itself to do the tracking. It is relatively easy to find fixed X and Y offsets for the star in relation to the centre of Saturn. Taking the pixel with maximum light level as the centre of Saturn, is not a good idea. To be sure reference is made to the same position of Saturn I used a mask (part of the image) to be fitted with least squares onto the next image (figure 10). Due to the large volume of necessary calculations, such a procedure only works out when bad tracking results in a slow (oscilating) drift, typical for the better amateur tracking devices. The resulting curve is presented in figure 11.
