Bradley-Sardin telecentric telescope for enhanced detection of the   aberration of stellar light
  A telescope specifically designed for the observation of the stellar aberration of light is proposed. It is distinctive in two main features: a lengthy collimated beam and an adjustable position of the photo-detector along the telescope axis, so the beam length-of-flight can be varied from zero to the telescope total length. This is achieved by means of a telecentric objective projecting the collimated beam up to a movable CCD camera. The spot position on a high-resolution photo-detector array is recorded, and the data are transferred to a computer and treated by a beam analyser software. The telescope aims to measure with high accuracy the aberration of stellar light due to the earth orbital motion. An alternative would consist of fixing the telecentric objective at the top of a cliff by means of an anti-vibration clamp with a high-precision directional mount. The detector would be fixed on a micrometric positioner, placed on the foot of the cliff at the beam position of fall. This way, the beam time-of-flight can be considerably increased, and hence the subsequent spot shift. For a beam length of 300 m the resulting shift would be of 30 mm, and so in a year the spot would describe a circle of 60 mm diameter. Optionally, a diode laser may be fixed at the centre of the telescope objective in order to contrast the behaviour of local and stellar light. 
G. Sardin