|
Most amateur astronomers have observed double stars at one time or
another. Many of you have favorites, like
Alberio or Epsilon Lyrae.
Splitting a close pair can be a test of your optics, eyes, seeing
conditions, and sometimes,
your patience.
Since the majority of stars in our galaxy are members of multiple
systems, it should come
as no surprise that some of the variables we
observe also have companions. I'm not referring to the unseen
companions
of eclipsing binaries or cataclysmic variables, but rather,
pairs of stars you can actually see.
These variable
doubles present their own challenges and rewards in
observing. The following is part of a long list of variables that have
very
close companions. These may cause observers some difficulty in
identifying and/or estimating the variable star in the field.
In fact,
I have included a few close pairs where BOTH components are variable!
CE LYR 1832+27
This variable
sits due west of its 113 comparison/companion.
Strangely enough, my star hop to this variable begins with a close
double
in the finder scope.
Z LYR 1856+34
Egad! This one can make you go blind. The 136 and 138 comparisons
are
very close to each other and close enough to the variable to cause
confusion. Pile on the fact that you need a magnifying
glass to see
the tiny star dots on the e chart, and you have a real puzzler in the
dark with your red flashlight! I
recommend using the f chart and high
magnification when it approaches minimum.
UU LYR 1901+27
I don't
recall having actually seen this faint Mira yet. It is
located very close, and to the SE of its 137 companion/comparison.
TU
AQL 1922+01
I found this one tricky to estimate when it was nearly equal to the
110 comparison/companion. You
can't defocus or they run together.
Nicely contrasting colors may be pretty, but they don't help much when
it comes
to making the call.
SW AQL 1946+12A
This Mira has a NE companion that can easily be mistaken for the
variable.
At maximum, SW Aql only gets to 13.3, so be sure you can see
both stars before making the call.
OW AQL 1946+14A
This Mira is parked right next to a 9th magnitude star. Picking it
out of the glare near minimum can be a test. Steady
seeing and high
magnification may be needed.
Z CYG 1958+49
This one isn't too hard to split from its 130
companion/comparison,
but it is in a rather confusing field. The entire sequence is riddled
with comparisons that are
themselves double. The 85, 105, 115, 121 and
133 comparisons are all close pairs. Be careful not to use the
combined
brightness when making the estimate using these stars.
SY AQL 2002+12
Beware the 14th magnitude impostor
due north near minimum. It's very
close. Lots of doubles in this field, including the 73, 95, 104 and
110 comparisons.
FG
SGE 2007+20 and ST SGE 2007+20A
Double trouble! FG Sge is often confused for its close neighbor to
the east.
What's more, the eastern companion may itself be variable.
As if that weren't enough, on the same chart is another devilishly
close
pair, ST Sge and its close buddy. Good seeing and high
magnification are needed when these stars are faint.
On
a side note, an article on FG SGE by Ron Royer was published in
1999 in JAAVSO vol. 27, no. 2, p. 146-147. It can be read
online at
the URL below:
http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1999JAVSO
..27..146R&db_key=AST&high=3b4f1b442624482
LX
CYG 2152+47A
I haven't had the pleasure of seeing this one near minimum. Its 138
companion was a good catch on
a steady night when LX itself was 9th
magnitude. This is another chart with lots of booby traps. For faint
comparisons,
the 140 near LV Cyg is a double and the 144 and 141 are a
close pair near LY Cyg, which is a close double also! Three variables
in
the Milky Way in Cygnus. Two with close companions and close
doubles as comparisons. My advice... take your time.
DV
CYG 1917+29, YZ VUL 1940+27 and DG CYG 2039+42
All deserve honorable mention in this region of the sky.
I would like to thank Georg Comello for his input and suggestions
for candidates for this article.
|
