Sky Reporter 
A Gift for Health 
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Getting Ready for Halley 
Scientists have already begun making plans to observe 
this born again and again comet, 
by Stephen P. Maran 
“We’ve been looking for the last three 
years and we intend to look again in the 
coming season,” said Michael Belton, 
referring to the current search for Hal- 
ley’s comet. An expert on planets and 
comets at Kitt Peak National Observa- 
tory in Tucson, Arizona, Belton is lead- 
ing an attempt to make the first sighting 
of Halley’s comet before its grand 
sweep past the earth and the sun in 
1985-86. 
Halley’s comet has passed this way 
before; its last trip was in 1910. There 
are several scientific reasons for trying 
to make the earliest possible sighting of 
this previously known comet on its up- 
coming trip; among them are the desire 
to determine its physical state while far 
from the sun, the opportunity of measur- 
ing the size of the nucleus before it 
starts shedding material and gaining in- 
creased knowledge of the comet’s orbit 
as a navigation aid for planned cometary 
space missions, and to assist in pointing 
the Space Telescope correctly. There is 
also the nonscientific reason that who- 
ever is first to sight the comet will be 
assured of a place in astronomical his- 
tory. The most famous comet observa- 
tion of all time was made by an eight- 
eenth-century German farmer, Johann 
Palitzsch, who was first to spot Halley 
on its trip through the inner solar system 
in 1758. Without that feat he would 
surely have remained unknown. Instead, 
Palitzsch is remembered in any number 
of historical accounts and books about 
comets. 
Palitzsch upstaged the professional 
astronomers of 1758 by sighting Hal- 
ley’s comet on Christmas Day, on its 
first return following the prediction by 
the English astronomer Edmond Halley. 
due back in 1985-86 
The return not only verified Halley’s 
prediction but also lent increased weight 
(if I may use that phrase) to Isaac 
Newton’s theory of gravity and the grav- 
itational effects on the motions of ob- 
jects in space. Needless to say, the re- 
turn had been eagerly awaited by the 
scientists of the world. So much so that 
Voltaire is said to have quipped that “as- 
tronomers never went to bed in 1758 for 
fear of missing the comet” (see “The 
Comet Syndrome,” Natural History, 
December 1980). 
This time around, however, the pro- 
fessionals are not about to be upstaged. 
Belton, for example, is using the 4-meter 
(159-inch) Mayall Telescope at Kitt 
Peak, equipped with a sensitive televi- 
sion camera that makes time exposures. 
Also, a group at the Mount Palomar 
Observatory in southern California is 
employing the famous 200-inch Hale 
telescope, together with an advanced 
solid-state detector “chip,” which is re- 
frigerated to within a few degrees of 
absolute zero to attain maximum sensi- 
tivity. No amateur, as far as is known, 
can command comparable instrumenta- 
tion. 
The predicted brightnesses of comets 
are always uncertain, as was underlined 
when great visibility was anticipated for 
comet Kohoutek (see “A Funny Thing 
Happened to Comet Kohoutek,” Natu- 
ral History, March 1974), but failed to 
develop. Nevertheless, for what it’s 
worth, the predicted brightness of Hal- 
ley’s comet this fall, when Belton and 
others will continue to search, is 24th 
magnitude. This is about sixteen times 
(or three magnitudes) fainter than the 
dimmest stars and galaxies on the Palo- 
mar Observatory Sky Survey, which 
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