The same CCD, a square 1024 pixel thick chip is moved between the two spectrographs. The nominal quantum efficiency curve of the Thomson THX31156 detector is shown above. The chip is square, 1024x1024 pixels, with the square pixel size of 19 microns. Cassegrain spectrograph Click here to see several photographs of the Cassegrain spectrograph. The orientation on the sky is fixed, E-W, and the spectrograph cannot be rotated.
Diffraction gratings Several gratings are in use.
They are designated by the number of lines per mm and a letter code. There are indications that the seeing is improving with time as the amount of heat generated by the Toronto megacity increases. These numbers are given here only for your guidance and are frequently subject to agitated disputes. The half-hour requirement results from our attempts to control the spectrograph flexure. In fact, longer exposures suffer also from numerous cosmic ray hits, so that we seldom expose for longer than 20 - 30 minutes.