Spectroscopy

A full report on the recently installed new VPH grisms is now provided on the ALFOSC web page. These new grisms are relatively large, and the ALFOSC grism wheel was modified to have all 3 VPH grisms installed at the same time.

The quicklook spectroscopic reduction script for ALFOSC has been upgrade to include a correction for the slit position when the standard wavelength solutions are applied to the extracted spectra. The precise slit position changes every time a slit is installed, which causes an apparent shift in the wavelength. Also, the automatic search for the target spectrum was modified to avoid the wrong identification of cosmic rays as a target.

A reported problem with the slow turn on of the ALFOSC He spectral calibration lamp was believed to be caused by a failing starter. Requesting spares from the manufactures Osram of the ST191 device they replied stating it is no longer manufactured and they could not suggest a direct replacement. Some normal fluorescent tube starters were tried but they did not turn on the lamp. After a lot of effort eventually a source of the ST191's was found in Sweden, and these were found to work properly.

Thomas Augusteijn 2016-05-05