N.B. See my ammendment to this page below. It now serves as an historical record of how things were from the late 1980's up until I was forced to take early retirement in 2002!
The rostered Duty Engineer (DE) takes over once the day staff leave site at 4pm and has the responsibility of resolving any problems that may occur during the night. The DE is available on site until 11pm and can then retire to bed, but can still be called out if a serious problem occurs. A room is allocated for the DE in a house near to the residencia; a short drive down from the observatories.
The night staffing has changed considerably over the years. There were once two Duty Technicians (DT) plus a Duty Officer on site. One technician was responsible for the WHT, the other for the INT (and the JKT when it was in operation). The Duty Officer was responsible for site safety and security, medical emergencies, etc. Due to financial constraints over the years, all those duties are now handled by the DE. The worse case scenario being someone getting injured or taken ill. Unfortunately, it has happened. For this reason, all staff on the DE roster must be trained in First Aid and CPR procedures and take refresher courses annually.
A Telescope Operator (TO) runs the WHT for the observers. He is responsible for opening the dome, moving the telescope, setting up the autoguiders and TV acquisition cameras, etc and when to close the dome if the weather turns foul. There is no TO for the INT these days and visiting observers not familiar with the telescope get help from an ING support astronomer for their first night. The INT observing system has been greatly refined over the years and operations including moving the telescope and running the autoguider as well as taking images can be performed from a single workstation.
When I started working on the night duty roster towards the end of 1986, I spent about 6 months with experienced engineers before going it alone. The WHT didn't start regular observations until 1988, but with only the INT and JKT in operation, there was still plenty to learn. The telescope control systems, acquisition and guidance units, spectrographs and image detectors, etc. It was not uncommon for a telescope or instrument control computer (a Perkin Elmer 3210/20) to break down and we had to fix these mini frame computers also. One of the more problematical pieces of kit in those days was maintaining the Image Photon Counting System (IPCS), the 'blue' detector on the INT spectrograph. It was certainly the most complex instrument at the time and sometimes difficult to repair. I for one was only too happy when it was decommissioned due to advancements in CCD's that could work with more efficiency at blue wavelengths.
Due to advancements in computer technology and image acquisition, the observing systems are a lot more reliable now than they were back in the 1980's. Night callouts to fix problems were quite common then. Perhaps it was more through luck that in the 16 years I worked as a DT/DE, I was woken up and called up to site only about five times. Other staff on the DT/DE roster equalled (or bettered) that number of callouts in a month! Most DT/DE's would retire to bed at 11pm, but being interested in astronomy, I got into the habit of staying up on site; often alongside the observers, until 1 or 2am. If any problems did occur (and during those hours they often did) I was already on site to deal with them. This probably accounts for my low number of callouts over the years. On one occasion I was woken up and managed to solve the problem over the phone. About an hour later, I got another call for a different problem which I also solved over the phone. I had just dropped off to sleep when the phone rang again! This time it was: To thank me for my help and that all was now working ok... I was NOT amused :-)
My first callout was by RGO astronomer Derek Jones to the JKT (21st May 1989 at 3:30am). The oil pump which lubricates the worms had failed. I crawled under the rising floor and asked Derek to switch on the pump. A jet of high pressure oil shot out of the pump splattering against the far end of the floor-well and almost hitting me also! My recommendation to Derek was to close the dome and retire for the night! The mechanics fixed the oil pump next day. A diaphragm had burst which had to replaced. A task that I couldn't have done in any case.
Many of the problems I encountered at night were simple to solve; some quite amusing. Like being called to the JKT because the visiting observer could not find any stars? Well, it does help if the mirror petals are opened! Another was a time when the WHT refused to move. The culprit being a metal framed chair had been 'picked up' during a slew and was jammed between the dome walkway and a Nasmyth instrument platform! The bent chair was put on display in the WHT control room for quite sometime afterwards and proved to be a good talking point!
Other problems could be more subtle? A call from a JKT visiting astronomer at first was a mystery. He told me he couldn't find any guide stars close to the object he wanted to observe yet he could find stars in the autoguider field in other areas of the sky? On entering the dome, the problem was solved. The observing floor was illuminated by a full moon and the telescope was pointing just a few degrees away from it. The expensive photomultiplier tube in the autoguider could be instantly destroyed by strong light and the over-illumination protection circuit was simply doing its job and had shut down the high voltage supply. I recommended that he selected one of his targets that was well away from the moon!
I was on duty the night of the 6th May 1999 when a potentially disastrous problem struck the WHT. We had fitted the prime focus imaging platform during the day and all was ok until we came to do the alignment of the CCD camera. The visiting observer was ex-RGO astronomer Max Pettini who I knew well. We had got the camera almost flat, but needed to do some focus runs as a final check. However, on moving the telescope focus the image quality didn't change. I also noticed that the focus position display was stationary, but the motors were definitely working as currents were being drawn. I spent quite a time looking into this and decided it was a mechanical problem, but needed a second opinion. I called Clive Jackman (the WHT telescope control specialist) who arrived on site about 1am. We couldn't check the mechanical drive of the focus as it was in-accessible, but we both came to the conclusion that probably a toothed belt or drive shaft had snapped. As the focus was very close to optimum, Max decided to observe in any case and I retired to bed at 4am.
It wasn't until I arrived back at the WHT mid-morning that the full extent of what happened became known. The mechanical staff had removed the prime focus imager and had rotated the top ring to gain access to the focus mechanism. The problem was obvious. A toothed belt tensioning pulley was missing, but where was it? It was found below the mirror cover petals and on the surface of (the once pristine) mirror was a gouge where the pulley had dropped plus some smaller dents. The pulley weighed several kilos and in retrospect, it was incredible the damage to the mirror was not greater. From what I recall, the optical quality of the mirror was not compromised and a couple of months later, a specialist came over from the USA to grind out the stress marks around the dents. Probably due to the thickness of the mirror (made of Cervit) it survived, but the outcome could have been disastrous if the mirror was a thin one as many are these days.
Looking back in my logbooks makes interesting reading, but the thing I'll never forget was on my first night alone as Duty Tech going up to the balcony in the INT dome and seeing the open aperture full of stars. I just stood there for a while taking in the experience. My thoughts turned to when I first saw the INT through the window of the visitors gallery at Herstmonceux in the early 1970's. If someone back then had told me that one day I would be looking after the INT at night, I would have never believed it...
Ammendment Since this page was written in 2006 - There have been quite a few significant changes with night operations at the ING. For several years now (and probably due to continual funding cutbacks!), there is no night or weekend technical support. The post of what was the WHT Telescope Operator (TO) who is often called a Night Assistant at other observatories has now been changed to an Observing Support Assistant' (OSA). The members in that group have been trained to resolve some of the common technical issues (e.g. rebooting computers or instrument controllers, etc) which in the past was left up to the rostered night Duty Engineer to address.
As briefly mentioned above, there is no night support for the INT and visiting astronomers get a night's training with a member from the support astronomy staff. For quite a few years, these have been astrophysics students doing their PhD who come out on a year sabbatical to gain observing experience.
As for the JKT, that is now run by the Southeastern Association for Research in Astronomy in the USA and has been fitted out with a new telescope control system (TCS) and camera and re-commissioned to work as a remote telescope now using the telescope's F/8 optics.
