Sky and Telescope - November 2015 - 31

ALL SKETCHES BY THE AUTHOR

Another problem we've run into
is the limiting magnitude. (This
refers to the faintest magnitude a
telescope can see.) That's because
our test pairs that are 4.0″ wide
and unequal by more than two
Σ2958
magnitudes have 9th- to nearly
10th-magnitude companions. A star
this faint is hard to observe with less than 100 mm, even
when it stands alone, unless the sky is quite clear. That
added complication shows up in our ﬁndings for Σ2958
(Struve 2958) in Pegasus: it's wider than Psi (ψ) Cygni
and no more unequal, but requires at least as much
aperture. I need 100 mm to see its companion, and even
with this much, all I see is a dim, nebulous globe beside
a muddy white star. I can't even see the companion of
5 Aurigae with that aperture, but Bill
Boublitz of Hanover, Pennsylvania,
an enormous contributor to our
project, can, describing it as "a
ghost of a thing . . . a faint, tiny,
ice-blue point."
90 Herculis
Still another problem we have
found is the tiny 1.0″ or 1.5″ separations for pairs like Σ2403 in Draco or Beta (β) 67 in
Cygnus. A pair this close should need at least 125 mm
and a scope that gives razor-sharp images, even if it was
made of equals; an unequal pair should need still more
aperture, and scopes larger than 125 mm are greatly
aﬀected by the sky. We just don't have enough observers
with large refractors or Maksutovs and excellent skies.
Boublitz was able to split both these pairs, as well as
equally hard 90 Herculis, with his
178-mm Maksutov. He describes
Σ2403 as "white [and] orange-gray,
16 & 17
split was easy [at 150×]." He saw
Draconis
Beta 67 as a "white star" with a
companion "that was quite dim
without any vivid color . . . just
sort of gray," but added that it "shows
some orange-brown at times." 90 Herculis appeared as
a "golden star with an orange fringe," with a "sparkling
medium blue diamond" next to it, and he considered it a
"very tough object," even for his 178-mm.
A much easier close pair that's also easy to ﬁnd is
Σ2054 in Draco: it's in the same low-power ﬁeld with
Eta (η) Draconis. My logbook says I needed 350× with
my 125-mm refractor to "just barely" split
it. At the opposite end of the diﬃculty
scale are Rho (ρ) Herculis, 17 Draconis, and Σ2671 in Cygnus. I'm
sure these are pairs for the smallest telescope, but we need more
Rho
conﬁrmations of this for 17 DraHerculis
conis. All are naked-eye stars easy

to ﬁnd and all split easily in my 60-mm
refractor. Rho Herculis was among
the ﬁrst double stars I ever observed,
many decades ago. I thought both
stars looked white, but 19th-century
observer Admiral Smyth considered
Psi Cygni
the companion "pale emerald." What
do you see? 17 Draconis will appear as
a wide double star in your ﬁnder scope, comprising 16
and 17 Draconis. I see 17 as "yellow-tinted white and pale
white," but the classic 19th-century observer T. W. Webb
called the companion "pale lilac." My notes call Σ2671 a
"bright white star with a gray smoke ball close beside it."
Psi Cygni is another ﬁne naked-eye star that some of
our observers have split with just 60 mm, but not me! My
only notes are from my 125-mm, through
which the pair appeared "brilliant yellow and ocean blue." Admiral Smyth
described it as "bright white [and]
lilac," however.
Hu 544 in Perseus is well placed
for viewing, sharing a low-power
Pi
Capricorni
ﬁeld with Alpha Persei. Boublitz
found it "challenging" to split with his
101-mm; he calls it "a tiny blue dot below
a blue-white primary [star]." He found nearby Σ389 in
Camelopardalis a "striking and lovely pair . . . cream
white and green" as viewed with his 178-mm, but saw
"hints of orange" for the companion with his 101-mm.
For Northern Hemisphere observers, Pi (π) Capricorni and h5188 in Sagittarius are about as well placed
as they're going to get. I found Pi Cap radiant white and pure silver, but Boublitz saw the companion as "ruddy
red or rust orange." He described
h5188
h5188 as a group of stars, because he
saw its very wide, faint companions
along with the main AB pair that's
our test object. Our other test pairs
visible now are deep in the Southern
Hemisphere. I can't tell you much about
them from our reports, because we have
so few southern observers.
We'd love to have you join us! To ﬁnd out more about
our project, visit http://is.gd/HaasProject and http://
is.gd/udstars. You can send e-mail to has103@comcast.
net, or write to me:
Sissy Haas
823 Reamer Ave. Ext.
Greensburg, PA 15601
U.S.A. ✦
Sissy Haas lives in a small city in western Pennsylvania at
the end of an unlighted dead-end street, but whether her sky
is dark depends on who rents the house next door.
Sk yandTelescope.com November 2015

http://www.is.gd/udstars http://www.is.gd/HaasProject http://www.is.gd/udstars http://www.SkyandTelescope.com

Sky and Telescope - November 2015

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