Sky and Telescope - April 2017 - 33

HD90696

Targets in
the Galactic Cirrus
Object

Dec.

4° × 12°

00h 10.0m

+22° 00′

Andromeda Shelf

5° × 3°

00h 45.0m

+41° 00′

0.5° × 2°

10h 40.0m

+73° 30′

1° × 4°

01h 30.0m

+30° 10′

0.5° × 2°

21h 30.0m

+12° 15′

Leo Triplet

1° × 3°

11h 20.0m

+13° 00′

Markarian's Chain

2° × 4°

12h 20.0m

+13° 20′

M64

2° × 4°

13h 00.0m

+21° 20′

Volcano IFN

1° × 2°

09h 40.0m

+70° 20′

M33 Bridge
M15 Nebulosity

that 90-minute exposures weren't long enough, as he himself had photographed some of Herschel's regions (especially
what we now call Barnard's Loop) - nebulosity that Roberts
claimed didn't exist (S&T: June 2016, p. 36).
In the 1920s Herschel's observations were taken up by the
Austrian-American astronomer Johann Hagen, the ﬁrst Jesuit
director of the Vatican Observatory in Rome. Hagen visually
surveyed the sky for so-called "cosmic clouds" using a 6-inch
f/15 refractor. He eventually claimed to have observed all 52
of Herschel's nebulae, results that were derided when presented to the Royal Astronomical Society in 1921 because the
clouds weren't detectable photographically. Hagen continued
to compile his list of faint clouds up until his death, coming
to believe that they covered much of the night sky. Hagen
was a true visual observer, favoring the visual record over
photographs and arguing that many hours of long exposures
couldn't match what he could see in minutes. He advised
astronomers to put away their cameras and look through the
telescope, lamenting that visual skills were a dying art.
In something of a plot twist, Isaac Roberts' widow, French
astronomer Dorothea Klumpke Roberts, collaborated with
Hagen that same decade, perhaps to rehabilitate her husband's
reputation, which suffered after his criticism of Herschel.
Despite Hagen's emphasis on visual observing, he joined
Klumpke to publish Roberts' photographs as Isaac Roberts' Atlas
of 52 Regions, a Guide to Herschel's Fields (1928). The photos
received attention and applause; even Edward Hubble, a sharp
critic of Hagen, suggested more images should be published.

Pleiades Bubble

Angel IFN

p BRIGHT EYES, DUSTY FEET The spooky streak of dust known as
the Angel Integrated Flux Nebula requires a very wide field of view. The
brightest star in its "head," HD 90696, lies about 5° 08′ northeast of
M81, 48′ south of star HD 92148, and 6° 13′ northwest of Lambda (λ)
Draconis.

Size

Angular sizes are from the author's observation logs and recent catalogs.
Visually, an object's size is often smaller than the cataloged value and varies
according to the aperture and magnification of the viewing instrument. Right
ascension and declination are for equinox 2000.0.

The French amateur Marcel de Kérolyr, who has been
called one of the greatest astrophotographers of all time, also
worked to detect Herschel's specters during this time period.
He successfully photographed some of Herschel's nebulosities, ﬁrst with a 5-inch (130-mm) f/4.6 Derogy portrait lens
from his "Astrophotographic Station" in Digne, Alpes-deHaute-Provence, then with a 32-inch (800-mm) reﬂector
from Forcalquier. In addition to the photos, which de Kérolyr
published in 1931, the work at Forcalquier resulted in a list
of visual observations of most of Herschel's original targets.
However, de Kérolyr's 1931 paper didn't make much of an
impact. Hagen had died a year earlier, and interest in his -
and Herschel's - observations of nebulous ﬁelds had all but
disappeared. The astronomical world lost this fascinating
thread reaching back to Herschel.

At the Eyepiece
My own study of Herschel's ﬁelds started with ﬁrst light
through my 6-inch f/2.8 telescope. The 21-mm Ethos 100°
apparent ﬁeld-of-view (AFOV) eyepiece dominates the tiny
scope; indeed, I offset the scope's center of gravity with the
massive eyepiece in mind (S&T: Sept. 2014, p. 72). I aimed
for the Pleiades, the Seven Sisters of mythology. The 4.3°
true ﬁeld of view swallowed the cluster. The Pleiades' stars
shone brilliantly through the eyepiece; the Merope Nebula
looked like a waterfall. I noticed a smudgy ring of grayness
surrounding the cluster at the edge of the ﬁeld. Was there
something wrong with my bafﬂing? Was there some sort of
s k y a n d t e l e s c o p e .c o m

* APRIL 2017

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Sky and Telescope - April 2017

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