Street lights cast shadow over Mt. Palomar telescope

The great 200-inch Hale telescope on Mt. Palomar is in danger. The threat doesn't arise from lack of funding or creeping obsolesence, but from city lights.

Light pollution, which washes out some of the stars astronomers want to study , is a long-standing problem. However, it has suddenly become a crisis for Palomar Observatory - because the City Council of nearby San Diego has reversed a decision to install a kind of street lamp that would lessen the unwanted glow.

The situation is serious enough for the amateur astronomy magazine Sky & Telescope to raise an alarm. It has taken the unusual step of sending news media advance copies of an editorial scheduled for its August issue. The editorial points out that San Diego's action, if it stands, could set an unfortunate precedent for other areas where astronomers are trying to reduce light pollution. Clearly, astronomers see more at stake than the effectiveness of Palomar Observatory, although that is important in its own right.

At issue is the kind of street lamp to be installed for general lighting. Astronomers would like lamps shielded so they do not throw light upward. What may be more important, however, is their preference for lamps that cast a monochrome light. It is fairly easy for astronomers to filter out sky glow whose light has only a narrow range of wavelengths.

Mercury vapor lamps, which have been widely used, shed a multicolored light that astronomers consider a menace. These lamps also are energy gluttons. Municipalities such as San Diego generally want to get rid of them. Sodium vapor lamps are often used for replacement. It is these lamps that are at issue in San Diego.

Sodium lamps come in two general types - high pressure and low pressure. The former emit multicolored light, which astronomers abhor. The latter cast a yellow glow with only a narrow range of wavelengths, which astronomers can filter. San Diego City Council, after much debate, had voted to replace the high-pressure units already installed. It is this decision that now has been reversed.

Robert Brucato, vice-director of Palomar Observatory, warns that, over time, the new San Diego policy could lead to ''catastrophic degradation'' of the observatory's capacity. What he and other Palomar officials find equally disturbing is some of the reasoning behind the San Diego decision. Besides cost savings, it was asserted during the debate that Palomar is becoming obsolete.

This is hardly the case. Palomar director Gerry Neugebauer has explained that the 200-inch telescope itself is merely a light-gathering facility for instruments placed at its focus. Thus, he says, ''. . . It doesn't go out of style.'' Furthermore, he notes that modern detectors are so much more sensitive than the photographic plates once used to study stars that ''the 200-inch can now see objects a hundred times fainter than it could when it was built.''

Space Telescope - a NASA instrument to be placed in orbit around 1986 - won't make a ground-based unit such as Palomar obsolete. Because Space Telescope will be above the atmosphere (whose turbulence limits observations from the ground), it will be able to see farther than any telescope before. Nevertheless, it will only supplement, not supplant, ground installations.

The Palomar telescope cannot readily be moved or replaced. Neugebauer has estimated it would cost $50 million to $100 million to duplicate the facility today - a sum he considers unlikely to be forthcoming. As for moving, he calls the present location ideal for the observatory. Making this point last September in the California Institute of Technology's magazine Engineering & Science, Neugebauer said conditions for star study are so good at Mt. Palomar that ''light pollution is the only factor that is detrimental to Palomar right now.'' In fact, he added, ''Without light pollution, we should without doubt be able to keep on using Palomar far into the next century.''

Built with the help of private funds from the Rockefeller Foundation, rather than federal money, and operated by Caltech, Palomar Observatory is, nonetheless , a valuable national resource. Although located in an area of rapid growth, it is immediately surrounded by national forest, so that urbanization won't creep right up to its door. Observatory officials believe they have a good prospect of holding light pollution to tolerable levels - if surrounding communities cooperate.

So they consider the example of San Diego particularly important. If the city shows it cares enough about the great telescope to cooperate in light control, other communities are more likely to do so.

Hardier wheat

Wheat farmers have long been plagued by a fungus disease called eyespot. No wheat variety has shown any substantial resistance to the fungus - resistance that could be transferred to other wheats.

Now a team of French and Spanish agronomists has successfully transferred such resistance from a species of wild grass to a line of commercial wheat. As they recently pointed out in Nature, this is a practical breakthrough for farmers - as well as an important experiment in basic plant science.

The scientists are G. Doussinault of INRA, Station d'Amelioration des Plants in Le Rheu, France, and A. Delibes, R. Sanchez-Monge, and F. Garcia-Olmedo of the Departmento de Bioquimica, ETS Ingenieros Agronomos in Madrid.

Other scientists have had trouble in trying to transfer the gene responsible for the resistance from the grass (Aegilops ventricosa) to commercial wheat. The French-Spanish team found one particular wheat (Triticum turgidum) that did successfully accept the grass gene. This wheat, in turn, became a ''bridge'' species that transferred the gene to other wheats.

Thus, by using techniques of plant breeding - not exotic ''genetic engineering'' - the researchers have come up with a method that they say ''should be immediately useful in converting susceptible wheat (varieties) . . . into resistant ones.''