ALPY in the red

Forums Spectroscopy A cautionary tale ALPY in the red

Robin Leadbeater

Note also that that the ALPY optics are specially optimised for the violet end and the sharpness deteriorates noticeably in the red/IR in any case due to chromatic aberrations. (The early  ALPY’s had an IR blocking filter to stop people operating in this region until it was removed after I pointed out the effect the terrible ripples in the passband of the filter had on the instrument response)