August 21 1961 - Astronomy on Television

For the fiftieth programme in The Sky at Night series, we attempted a rather ambitious outside broadcast from Patcham, near Brighton, where G. A. Hole, world-famous as an optical expert, has set up a 2 4-inch reflector. Preparations took some time, and various new devices had to be made, many of which were planned and constructed by George Hole himself. We hoped to show some spectacular objects, including the planets Jupiter and Saturn.

Well before the time when we were due to start, massive vans full of equipment started arriving at Patcham, and the whole area was a hive of activity. The weather was tactically uncertain, but we hoped for the best. Perhaps we were over-optimistic; after all, we had been successful on previous occasions - but this time we met our Waterloo, and the clouds seemed to take a fiendish delight in checkmating us. Each time we swung the telescope toward a star or planet, the object disappeared behind a cloudy veil. We attributed it to the well-known Spode's Law, which states, broadly, that 'if things can go wrong, they do'. Nevertheless, we learned several useful things from the fiftieth Sky at Night, and the knowledge gained was put to good use on subsequent occasions.

Early astronomers had to carry out all their observational work by means of the naked eye. They naturally constructed measuring apparatus, but without optical aid their scope was limited, and was more or less confined to positional studies. It is true that some of the old star-catalogues, notably Tycho Brahe's, were of remarkable accuracy considering the circumstances in which they were drawn up, but even Tycho could find out nothing about the physical nature of the planets and stars.

The invention of the telescope, and its application to the sky by Galileo in the winter of 1609-1610, changed the whole picture, and astronomy entered a new phase. Yet still there were difficulties to be overcome; the human eye is notoriously unreliable and easy to deceive, and to make a permanent record involves drawing, which introduces still further errors. Personal bias is always hard to eliminate.

Next came photography, which led to an equally great revolu­tion in astronomical technique. Most research is now carried out photographically, and the world's greatest telescopes, such as the Palomar 200-inch reflector, are used mainly as giant cameras; it is seldom that anyone looks through them directly. Since then there have been other developments: for instance radio astronomy, which began only in the early nineteen-thirties when Karl Jansky first detected radio waves from the Milky Way, has yielded infor­mation which would have been almost impossible to obtain by any other method.

The lesson behind all this is that astronomy is only too ready to make use of any fresh technical development. Television, too, may play its part, particularly when it becomes possible to establish unmanned observatories in space; there have already been some spectacular triumphs, notably the sending-back from Lunik III of the photographs of the reverse side of the Moon. But so far as 'conventional' astronomy is concerned, television has yet to play an important role.

Things are different when we turn from technical research to the dissemination of information on a more popular level, and this raises a fundamental point. There have been people who have objected in principle to the popularization of astronomy, on the grounds that it can give only a picture of events which is incomplete and must therefore be distorted. It is perfectly true that astronomy is essentially mathematical, but it is also true that anyone, however badly versed in mathematics, can take an intelligent interest in it; and provided that no attempts at over-dramatization are made, it is possible to give an account of astronomical research which is accurate so far as it goes.

The ideal solution, of course, is to look at the celestial objects direct through a telescope. Unfortunately this is not possible for everybody. Telescopes are not cheap; there are few public observatories in Britain (a deficiency which should certainly be remedied), and city-dwellers are at a hopeless disadvantage. It is therefore of definite value to present television programmes in which 'direct' pictures are shown.

The idea is not new, and some years ago both the Moon and the planet Jupiter were successfully televised. It could not be expected that the pictures on the screen would be comparable with those obtained by an observer at the eye-end of a telescope, but they were much better than nothing, and in their way they were more effective than any photograph could be.

Since the beginning of regular astronomical programmes on BBC television, several direct views have been obtained. The Moon was shown from Hampstead Observatory, using the 6 inch refractor there, and in the earlier part of 1961 Venus was shown from G. A. Hole's observatory at Patcham, near Brighton in Sussex. There was also the ambitious programme connected with the total solar eclipse of February 1961, when Eurovision links were set up, and totality was shown three times - from St Michel in France, Florence in Italy, and Mount Jastrebac in Jugoslavia. In addition to the popular appeal, valuable experience was gained in connection with exposure times and similar details, and it is hoped that this information will be of definite use in the future.

For televising relatively faint objects, such as planets, it is necessary to use a powerful telescope with considerable light-grasp. The 24-inch reflector built by G. A. Hole is particularly suitable, since it was constructed largely for lunar and planetary work - in contrast to most telescopes of comparable size, which are designed principally for studies of stars and remote galaxies.

The telescope, constructed entirely by Hole, is not in an observatory, but is situated in the open. It is of course equatorially mounted, and has a most efficient drive, so that the object under study is held firmly in the field of view. The necessarily long focal length raises practical difficulties, which have been overcome in an ingenious manner. There are two optical systems in use. Normally the telescope is used as a Cassegrain, but there is no hole in the main speculum; an extra mirror diverts the light-rays to the side of the tube, near the lower end, where the eyepiece is placed, which makes observing extremely convenient, though it does admittedly entail an unfamiliar reversal of the image. When conditions are really good, and very high magnifications may be used, the Cassegrain mirror is swung down into a compartment let into the telescope tube, and the Gregorian secondary, at the upper end, comes into action. It is therefore possible to change the telescope from a Cassegrain into Gregorian in less than sixty seconds.

For television purposes, a lightweight television camera is attached to the eyepiece end, and the picture is obtained direct. No difficulty has been experienced in centring the picture, and so far as the Moon and brighter planets are concerned there is plenty of light available. During tests excellent pictures have also been obtained of stellar objects such as binary stars. Disturbances due to atmospheric tremor are always noticeable, but no more so than under conditions of direct visual observation, and certainly help the beginner to understand at least some of the difficulties which practical observers have to face.

When a programme of this sort is being planned, the weather has always to be taken into account; a layer of cloud or a patch of fog at the wrong moment can ruin things completely, and though a tele-recording made earlier is a reasonable substitute for a direct picture, it cannot be regarded as 'quite the same thing'. For the programme of 21 August 1961, when it was planned to show the Moon, Jupiter, Saturn, and two double stars (Mizar and Beta Cygni), all possible precautions were taken, and a television camera was also attached to the 36-inch reflector at the Royal Observatory, Edinburgh, which has a light-grasp even greater than that of the Patcham instrument. The co-operation of the Edinburgh authorities was much appreciated.

On this occasion, unfortunately, the sky at Patcham was over­cast, and no direct pictures were obtained, though views of Jupiter and Saturn obtained earlier in the evening were shown. At Edinburgh, both the giant planets - now well to the south of the celestial equator - were inconveniently low, and conditions were not good, but it was possible to switch through and obtain some 'live' pictures. Ironically, the clouds cleared from Patcham a few minutes after the programme was over, and within half an hour we were seeing some superb views of the lunar mountains and craters.

Direct television in astronomy is certainly of general popular interest, but it must also be linked with events in the future. It seems that the idea of a fully fledged 'space-station' with a per­manent crew is becoming less and less plausible, and it is much more likely that the first space observatories, at least, will be unmanned. Unless they can be brought back to Earth, which will be a truly Herculean task, the pictures must be sent back - and this is where television will come into its own, admittedly in a somewhat modi­fied form. The present series of experiments may therefore prove to be of real value in the foreseeable future.