Rewriting optical elements

摘要

The observatories of tomorrow will necessarily be equipped with robotic facilities which will ease the use and allow a full time schedule optimization. Herein we present the application of organic materials with photochromic properties in astronomical spectrographs. Photochromism is the reversible transformation of the optical (in particular the color) and spectral properties of a material by suitable light. Organic photochromic materials can be cast in thin layers (tens to hundredths of microns) where a chosen pattern can be written leaving the layer with two areas showing different refractive index and absorption/transmission spectra. We used the opaque/transparent property of such photochromic materials to build rewritable focal plane mask for MOS spectroscopy. They were tested in laboratory and then sky tests were successfully carried out by using the AFOSC camera (Asiago Faint Object Spectrograph and Camera) of the 1.8 m telescope at Asiago Observatory. The results obtained are encouraging and the first MOS writing device is now in use at the astronomical observatory of Asiago.