Letter to the Editors

Dear Editors

I read with interest Dr Brian Robinson's obituary by Helen Sim and Wayne Orchiston in the ATNF News Issue No 54, Oct 2004. There is a paragraph on page 12 that I felt reflects poorly on my long time colleague, John Murray. It refers to a blunder in which Brian and I were involved. I feel obliged to give you my version of that sad event.

It is quite true that John Murray had been checking the multi-channel filter bank when, unknowingly, Brian and I started our observations of the OH line radiation in Sgr B2. No difficulty there, John stopped work as soon as we asked. When you have as careful and meticulous an engineer as John on the job you are only too grateful for his interest in the equipment (which, incidentally, he had designed and built with the aid of a superb wiring performance by a young apprentice, Mal Sinclair!). It would have been a truly extraordinary occurrence and totally out of character had John not returned all of the units he had been checking.

The blunder was made by no one else but me — and it happened this way: The filters were followed by a corresponding set of synchronous detector units. The observation showed the very deep and widespread absorption of OH in Sgr B2. However, channel 31 (if my memory is correct on the number) remained on the zero line. That very unit had given trouble in the past and in view of that wide absorption I was idiotic enough to declare that we should ignore channel 31 and look into its trouble later, meanwhile to carry on with the observations. I state the obvious by writing that at the time we never expected to see anything but absorption. The narrow OH emission line occurred in channel 31 and was strong enough to return the level from the deep absorption back, not part of the way or beyond, but just to zero. So a combination of bad science and bad luck caused the disaster.

Yours sincerely

R X (Dick) McGee

Editors' note: We thank Dick McGee for providing us with this interesting account of the day in 1964, when the OH maser line was seen in emission at the Parkes radio telescope, but not recognised as such. This occurred a year before the famous 1965 Nature paper by Harold Weaver et al. announcing the discovery of OH maser emission.