Sky and Telescope - June 2016 - 40

ROGELIO BERNAL ANDREO / DEEPSKYCOLORS.COM

Early Pro-Am Split

ORION HEAD TO TOE The vast arc of Barnard's Loop encircles Orion's Belt and Sword in this extremely deep image stack
taken by Rogelio Bernal Andreo. Amateurs dominate wide-ﬁeld
astrophotography today.

shown," he wrote of the huge, ghostly arc now known
as Barnard's Loop, "especially the region described by
Herschel. . . . There is therefore no question but that this
nebulosity exists where Herschel saw it."
In closing, Barnard thrust a dagger at Roberts's competence, reminding readers that it was "with the same
instruments described in his present paper that Dr.
Roberts failed to get any trace of the exterior nebulosity
of the Pleiades, which had been shown by four observers
with four diﬀerent instruments not only to exist, but to
be not at all diﬃcult objects."
Moreover, Max Wolf at the University of Heidelberg
had recently taken a wide-ﬁeld image of the same Region
27 using Heidelberg's new 16-inch astrograph. The
picture showed, with remarkable clarity, not only the
familiar Orion Nebula and the diﬀ use Horsehead complex around Zeta Orionis, but also the feathery, winding
form of Barnard's Loop.
Where, 15 years earlier, Isaac Roberts had astounded
astronomers with his breakthrough image of the Andromeda Nebula, he was now confronted with an equally vivid
portrait of a celestial object that he claimed wasn't there.
The Heidelberg 16-inch was neither the "small toy" nor
40

June 2016 sky & telescope

"child's lantern-lens" that Roberts had called Barnard's
instrument. And Wolf's exposure time of 6¼ hours
eclipsed Roberts's own 90-minute standard. (Wolf's pièce
de résistance would come in 1911 with a 24-hour exposure
of the Andromeda Nebula's spectrum, accumulated over
twenty nights.)
Roberts oﬀered the weak suggestion that both Wolf
and Barnard had targeted the wrong object! If not that,
then maybe the apparition on their plates had arisen
from atmospheric glare or reﬂections in the optics. Had
he accepted the verdict of his own eyes, he would have
recognized that a 90-minute exposure under moist, semitransparent English skies might indeed be insuﬃcient
to capture a low-contrast space cloud, especially when it
overran the border of his plate. He clung to the misconception that if he exposed long enough to capture the faint
stars William Herschel had seen, then Herschel's faint
clouds should appear as well. In fact, Barnard announced
that he did see traces of extended nebulosity on Roberts's
plates, a claim Roberts himself denied.
The nebular feud ended abruptly with Isaac Roberts's
death in 1904.
This episode is often remembered for how it symbolized astronomy's widening professional-amateur
divide around the turn of the 20th century. But the
real meaning is a bit diﬀerent. Barnard, a self-taught
grade-school dropout, was something of an über-amateur
himself. Rather, the skirmish and its outcome reﬂected
astronomy's move toward professionalization and more
rigorous scientiﬁc standards. In his drive to become an
eﬀective researcher, Barnard aligned his working methods and critical judgment to those of university-trained
astronomers. His knowledge base was largely empirical, but it was structured eﬀectively, in a way one learns
in the halls of academia. When Barnard criticized Isaac
Roberts for calciﬁed thinking, for not keeping up with the
technical literature, and for shrugging oﬀ big gaps in his
knowledge, he was enumerating the hallmarks of a poor
scientist. That Roberts was an amateur was not the issue.
Today, E. E. Barnard and Isaac Roberts are invariably
linked to the photographic catalogs they bequeathed to
astronomy. Despite Barnard's victory over Roberts in
their long public feud, neither catalog stands higher
than the other. Both are examples of the era's highest
scientiﬁc artistry. Image scale was the diﬀerence: where
Barnard portrayed the broad skylines of the galactic
metropolis, Roberts captured the façades of its notable
individual structures - two astronomers, no longer at
odds, but complementing each other. ✦
Alan Hirshfeld is a professor of physics at UMass Dartmouth, an associate of the Harvard College Observatory,
and a historian of astronomy. His most recent book is
Starlight Detectives: How Astronomers, Inventors, and
Eccentrics Discovered the Modern Universe.

http://www.DEEPSKYCOLORS.COM

Sky and Telescope - June 2016

Table of Contents for the Digital Edition of Sky and Telescope - June 2016