The following explains why the light kept switching on and off when Lee and I changed the plug at RAG mid-monthly meeting last Friday!
It also explains the black ring under the lamp – this appears to be so that it can fit over 2 inch end of a spectrograph – will it do same on my CCDSPEC?
Notes on DADOS Calibration lamp
The Neon calibration lamp only shines in the dark due to a twilight switch. So incidence of extraneous light while taking spectra of this Neon lamp is avoided. Please fix the Neon lamp with its adapter directly at the 2 inch entrance of the DADOS spectrograph to focus DADOS and to take reference spectra. The brightness of this Neon lamp is adequate in this configuration.
However, the lamp is too faint to be used in front of a telescope. The visually perceived color “Neon red” is a quite unique color between dark-orange and light-red due to the spectral distribution of the emission lines.