Sky and Telescope - June 2017 - 50

JUNE 2017 OBSERVING
Celestial Calendar

(AAVSO). An automated camera on a
telescope, clicking away tirelessly while
you observe something else (or snooze
indoors), results in far more accurate
brightness measurements, and therefore timings, than eyeball estimates
used to do. And an automated camera
can record a high-quality light curve
of a star's entire pulse, which may be
rather different than the previous pulse
just hours earlier.
To get a taste for these stars, on
+66°

55 Dra

62

+65.5°

104

101

+65°

XZ Dra
96 -106

112

109

these pages are comparison-star charts
for three RR Lyraes in easy reach of
amateur telescopes.
Set up at least an hour before a
predicted maximum. About every 10
minutes, make a very careful estimate
of the variable's exact brightness with
respect to comparison stars around it,
labeled on the charts with their visual
magnitudes to the nearest tenth with
the decimal points omitted. Do not let
yourself be inﬂuenced by what you saw
a few minutes ago; each estimate must
be unbiased and independent. You'll
likely see faster action than amateurs
usually observe anywhere else beyond
the solar system.
Watch out; this project could get you
hooked enough to buy an astrocamera,
learn how to do automated photometry,
and change your nights forevermore. If
you'd like to dive in, read the AAVSO's
CCD Photometry Guide at aavso.org/
ccd-photometry-guide and then write
to Samolyk care of aavso@aavso.org.
Listed below are Universal dates
(bold) and times (in hours) for maxima
predicted to happen well within dark
hours for at least part of the continental
United States and southern Canada.
Times are rounded to the nearest 0.5
hour to avoid biasing what you see.

Maxima of VX Herculis
Period = 0.4553595 day

105
19h 10m

May 1, 4.5; 4, 9.0; 5, 7.0; 6, 5.0; 9, 9.5;
10, 7.0; 11, 5.0; 12, 3.0; 14, 9.5; 15, 7.5; 16,

117

70
98

+19°

101

73

37

84

112

79

VX Her
99-112
104

γ Her

90

107
112

+18°

50

16h 30m

J U N E 2 0 1 7 * SK Y & TELESCOPE

16h 25m

5.0; 17, 3.0; 19, 9.5; 20, 7.5; 21, 5.5; 22, 3.5;
25, 8.0; 26, 5.5; 27, 3.5; 30, 8.0; 31, 6.0.
June 1, 3.5; 4, 8.0; 5, 6.0; 6, 4.0; 9, 8.5;
10, 6.5; 11, 4.0; 14, 8.5; 15, 6.5; 16, 4.5;
20, 6.5; 21, 4.5; 25, 7.0; 26, 5.0; 30, 7.0.
July 1, 5.0; 2, 3.0; 5, 7.5; 6, 5.0; 10, 7.5;
11, 5.5; 12, 3.5; 15, 8.0; 16, 5.5; 17, 3.5;
20, 8.0; 21, 6.0; 22, 3.5; 25, 8.0; 26, 6.0;
27, 4.0; 30, 8.5; 31, 6.5.

Maxima of XZ Draconis
Period = 0.467497 day
May 1, 4.5; 2, 3.5; 7, 9.0; 8, 8.0; 9, 7.0;
10, 6.0, 11, 4.5; 12, 3.5; 17, 9.5; 18, 8.0; 19,
7.0; 20, 6.0; 21, 5.0; 22, 3.5; 27, 9.5; 28, 8.5;
29, 7.0; 30, 6.0; 31, 5.0.
June 1, 4.0; 7, 8.5; 8, 7.5; 9, 6.0; 10, 5.0;
11, 4.0; 12, 3.0; 17, 8.5; 18, 7.5; 19, 6.5; 20,
5.5; 21, 4.0; 27, 9.0; 28, 7.5; 29, 6.5; 30, 5.5.
July 1, 4.5; 7, 9.0; 8, 8.0; 9, 6.5; 10, 5.5;
11, 4.5; 12, 3.5; 17, 9.0; 18, 8.0; 19, 7.0;
20, 5.5; 21, 4.5; 22, 3.5; 27, 9.0; 28, 8.0;
29, 7.0; 30, 6.0; 31, 4.5.

Maxima of XZ Cygni
Period = 0.466473 day
May 3, 9.5; 4, 8.0; 5, 6.5; 6, 4.5; 10, 9.5;
11, 8.0; 12, 6.0; 13, 4.5; 17, 9.5; 18, 8.0;
19, 6.0; 20, 4.5; 24, 9.5; 25, 8.0; 26, 6.0;
27, 4.5; 31, 9.5.
June 1, 8.0; 2, 6.0; 3, 4.5; 4, 3.0; 8, 7.5;
9, 6.0; 10, 4.5; 11, 3.0; 15, 7.5; 16, 6.0; 17,
4.5; 22, 7.5; 23, 6.0; 24, 4.5; 28, 9.5; 29,
7.5; 30, 6.0.
July 1, 4.5; 6, 7.5; 7, 6.0; 8, 4.5; 13, 7.5;
14, 6.0; 15, 4.5; 20, 7.5; 21, 6.0; 22, 4.5; 26,
9.0; 27, 7.5; 28, 6.0; 29, 4.5.

Lunar Occultation
º Late on the night of May 31 -
June 1, telescope users in most of
the U.S. and Canada can watch the
dark limb of the first-quarter Moon
occult Rho Leonis, magnitude 3.8.
Times for hundreds of cities and
towns are at lunar-occultations.
com/iota/bstar/0601zc1547.htm.
The star is binary, magnitudes 4.3
and 5.4, but with its separation of
only 0.1″, the two steps will happen
only about 0.2 second apart or less
at most locations.
http://www.aavso.org/ccd-photometry-guide http://www.aavso.org/ccd-photometry-guide
Sky and Telescope - June 2017

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