STF specializes in manufacturing of Maksutov-Cassegrain telescopes. There are two Mirage models currently manufactured: Mirage 7 is 7" and Mirage 8 is 8". Both models can be manufactured with different wave front quality: 1/6, 1/8 or 1/10.
The manufacturing of these telescopes is controlled on nterferometer at all stages which results in superior quality of the wave front (1/6, 1/8, 1/10 and better) and a high resolution. The telescopes have precise mechanics preventing image shift when reversing the focusing. Collimation is not affected during the transportation. Anti-reflective paint and thread on the inside surface of the telescope allow to make high-contrast pictures of the night sky. All these qualities along with compactness, small weight and a reasonable price earned high regard for these telescope among astronomy enthusiasts.
Mirage telescopes are Maksutov-Cassegrain telescopes. The optical scheme is shown below.
It consists of two mirrors: the main mirror - 1, the secondary mirror - 2 and a meniscus lens - 3.
The advantages of this system are:
1) Compactness. With the focal length and light collecting aperture being the same this scope is 3,5-4 times smaller than the scopes with the same focual length but without central screening.
2) Focusing is by movement of the main mirror, this prevents transverse shifts of the image when reversing. This design is not affected by the weight of accessories, which is an issue with the telescopes with focusers.
3) The movement of the main mirror allows changing the back focus from 90mm to 290mm, which means that the focal surface can be shifted within 200mm. This makes it possible to use practically any accessories.
4) The diameter of the diffraction spot is 8-10 mkm. This allows to get celestial images of great quality.
5) The telescope is made of a whole aluminium tube making it firm and rigid.
6) Each scope is tested on the interferometer and has a certificate with the inerferogram, in which the wave front error is given in wave length. fractions