Optical telescope
"Observable world" describes what can be seen using a telescope, when viewing an object or range the observer may use many different techniques. Understanding what can be viewed and how to view it depends on the field of view. Viewing an object at a size that fits entirely in the field of view is measured using the two telescope properties—focal length and aperture, with the inclusion of an ocular eyepiece with suitable focal length (or diameter). Comparing the observable world and the angular diameter of an object shows how much of the object we see. However, the relationship with the optical system may not result in high surface brightness. Celestial objects are often dim because of their vast distance, and detail may be limited by diffraction or unsuitable optical properties.
Observatory Naef Épendes
The invention of the telescope in 1608 and the subsequent improvements in optics led to the revolutionary progress of the 17th and 18th centuries. We call this type of telescope a refractor because it deviates the light coming from an object in such a way that its image is reversed ; observation is done through an eyepiece at the end of the tube, which allows magnification of the image. Bequeathed by Mr. Robert A. Naef, the observatory's precious telescope is a Reinfelder & Hertel with a diameter of 162.5 mm and a focal distance of 1435 mm - this allows a magnification of X150.