Abstract
I described our reconnaissance trip to the Canary Island telescopes in the May 1995 edition of Physics Education. Our intention was to take students to the islands in the summer of 1995, to carry out some astronomical research. Although this time scale proved to be too short, the Michaelmas term half-term proved suitable, so finally on 24 October the party of 13 students and 3 staff assembled at Gatwick for the flight. The group members, who had each paid £350 for the trip, were from Oundle, Oakham, Woodbridge, Bancroft's and Highgate schools, with myself, Stephen Cottrell, head of Physics at Woodbridge, and Thomas Hietzker from Bancroft's, who is a biologist. The Canary Islands' flora and geology make the islands ideal for a joint sciences/geography department expedition.
Our £110 flight to Tenerife arrived at 1.30 am, so after sleeping on airport chairs, we took the bus to the north airport and flew to La Palma. On arrival at midday we went to the Royal Greenwich Observatory sea-level offices. The RGO own several flats in the same building and they had kindly let us stay for two nights. The drive to the 2400 m observatories in a white-out did not bode well for observations: we had only my own small portable telescope, tripods and cameras. However, the Instituto de Astrofisica de Canarias had agreed to our using the 0.5 m Mons telescope on Tenerife, so all was not lost.
Splitting into two groups, one half were shown around the HEGRA group's latest Cerenkov telescopes by Dr Stella Bradbury, an English physicist from the Max Planck Institute. The two new 36-mirror telescopes collect Cerenkov light from cataclysmic cosmic events and focus it onto photomultiplier tubes. The computer display shows which of the 36 segments of the instrument are receiving radiation. However, as other faint light sources could register, only when two adjacent photomultiplier tubes are triggered does the display register an event. Often, nearly half the segments are triggered and the display is updated every few seconds. Although the two operative units are only at the test stage, eventually the group of five telescopes will have their signals correlated to help locate the direction of the possible source in the sky and match it to any optical phenomena also visible, e.g. a supernova explosion.
The second group walked up to the 4.2 m William Herschel Telescope where conditions were too poor for it to operate; this allowed the dome lights to be put on and the 100 tonne instrument was silently manoeuvred for us to see its main mirror. We were shown the CCD camera and cryostat at the Cassegrain focus of the telescope then the massive 3 tonne spectrometer at the Nasmyth focus on one side of the main platform. Suffering from the altitude and cold wind, we swapped with the HEGRA party for the second tour. At the Residencia, which was clear of the mist, we were offered a sight of Venus and a crescent moon setting in the west, with Jupiter higher up.
Back at sea level we bought souvenirs and found a full size replica of Columbus' ship, the Santa Maria, in dry dock in the middle of one of the main roads! On the mountain again, we drove right to the top of 'El Roque', around bends we didn't think the bus could negotiate, and between clouds whisking up the Caldera we could see its floor, 2000 m below us! From there we wandered over to the Isaac Newton Telescope building, which contains the main ING offices for a tour of the 2.5 m INT. This telescope was originally built for use at Herstmonceux in the UK, but was moved to La Palma when the site opened in 1987. It has an equatorial mount, suitable for use on 'smaller' telescopes, and a similar CCD camera to the WHT. Near the Residencia flats we set up cameras on tripods and a 90 mm Maksutov telescope, looking at the moon and Jupiter with all four Galilean satellites visible. Borrowing a 102 mm refractor from the HEGRA group, we just managed to discern Saturn's rings. Turning to fainter objects we found M31, the Andromeda galaxy, and its faint neighbour in Triangulum, M33. Finally, I had my first glimpse of M57, the `Ring' nebula in Lyra. Quite a few successful photos were taken.
After the flight back to Tenerife we arranged to tour the 'Tenerife Experiment' with Dr Bob Watson next day. It was a struggle with our baggage to get to the hotel in Santa Cruz, the capital of Tenerife, which is well stocked with inexpensive restaurants. Saturday morning saw us boarding a fleet of five Mercedes, which drove through the varied landscape to the weird, wind-eroded lava rock on the slopes of Mount Izana. There was just time to settle into our rooms before meeting our guide. As well as showing us the three twin-horned receivers of the 'Tenerife Experiment', which measures fluctuations of the order of 1 part in 100 000 in the cosmic microwave background (CMB) radiation, there were two new instruments. Firstly, a 6 m dish, jointly operated with George Smoot of COBE fame, receives at 5 GHz, with a beam width of 3°. Its axis is angled at 30° to the vertical so that it covers a 60° width of the sky in one day. The second new receiver is a twin-horned interferometer operating at 33 GHz, with a small base length for higher sensitivity. Operated jointly with Queen Mary's College, Westfield, with its surrounding aluminium reflecting shield, it is a similar design to the CAT interferometer prototype at Cambridge. A full-sized version of the latter is also rumoured to be heading for Tenerife, making the observatory the world's centre for CMB research.
After dinner we climbed the volcanic shingle trail to the Mons telescope building, where we settled down to wait for darkness and the sky to clear, but our bad luck with the weather continued. The telescope was built for the Université de Mons, France and is an f15 Cassegrain design of 0.5 m primary mirror, using a standard 2 inch diameter eyepiece. Although its dome and equatorial mount are motorized, rough positioning is by hand and swinging a 1 tonne instrument around in a small dome is by no means easy! When a break in the clouds finally appeared around 2.00 am, it was a struggle to guide it onto the Orion Nebula, M42, but the clarity of view made the effort worthwhile. The four Trapezium stars in the middle were seen with pin-sharp focus and the details of the wispy nebula around were as clear as one sees in photographs. Unfortunately, the camera left in the accessory cupboard would not work and there were no adaptor rings for our own, so we could not record this spectacle, but retreated to bed at 5.30 am.
Figure 1. The group by the Mons telescope building.
The weather closed in completely for our final day at the observatory. In the afternoon we explored the area, but being Sunday the Spanish solar observatory was closed. We had more luck at the VTT, or German Vacuum Tower Telescope, where we were able to see the coelostat mirrors at the top of the 100 m tower and the isolated laboratory above the spectrometer, which goes 60 m underground. The sky was cloudy so the site manager, Dr Michel Serra-Rickart, showed us their all-Spanish 0.8 m telescope and Carlos-Sanchez infrared telescope, made by Imperial College. Dr Serra-Rickart was impressed with our notes and the Canary Island Observatories workbook. He approved of astronomy being part of the National Curriculum and that Astronomy/Cosmology modules are available at A-level. There are plans to add a CCD camera and spectrometer to the Mons, improving its range of use, and the IAC are keen to receive more European students at the Observatory.
On Monday, after five taxis and two buses, we arrived at Los Christianos, in the south of the island, where the temperature was 26°C, the sky clear and we were due for a rest. All too soon it was time to return home to a cold London morning at 6.30 am. Back in the physics department by break on Wednesday 1 November I found a phone message from the European Southern Observatory near Munich: a student and I had won a national competition for a free trip to Munich and a week of professional astronomy! Two weeks later we were off again.
Thanks are due to the schools, IAC, RGO and PPARC who helped in the success of this trip. The Canary Islands Telescopes workbook and details to help organize your own trip are available from the author, Oundle School, Oundle, Peterborough PE8 4BN.
Richard Field Oundle School, Peterborough