Astrophotography by Anthony Ayiomamitis

Differential Photometry - V1193 in Cygnus

A variable star, as its name suggests, is a star whose magnitude varies intrinsically, in contrast to eclipsing binaries whose magnitude varies as a result of one star in the binary system eclipsing the other. True variables are one of five types, namely Mira stars, semiregular stars, cepheids, eruptive variables and, finally, cataclysmic variables. Minimum to maximum magnitude can range from days to many months with some variables displaying irregular periods.

A popular method for the study of variable stars, particularly short-term variables, is by the use of the technique known as "differential photometry". Rather than measure the (variable) magnitude of a variable star on an absolute scale, measurements are made over time relative to one or more non-variable star(s) and these differences are then plotted so as to study and illustrate the relative or differential change in magnitude. Due to the very large number of variables stars, the field of differential photometry represents one of the key fields in astronomy whereby the amateur astronomer can make a meaningful and long-lasting contribution to both science and astronomy.

More recently, the search for extrasolar planets (over 925 discovered so far) has identified yet another interesting application for the practice of differential photometry whereby the minute drops in magnitude of a star hosting an exoplanet are studied. Further details for the interested party are available here.

Note: The eclipsing binary star V1193 Cyg is a quick eclipsing binary variable star with a period of 0.50376561 days and which involves a delta mag of 0.5 (p) magnitudes during this brief time interval. The variable nature of V1193 Cyg was first reported by Hoffmeister in 1963 along with many other new variables in the vicinity of 33 Cyg and other fields of view. V1193 Cyg is an W Ursae Majoris-type eclipsing system where the ellipsoidal components are virtually in contact with each other and, hence, for its classification, namely "EW". Further details from the International Variable Star Index are available here whereas an AAVSO finder chart is available here.

Image Details
Light Curve for V1193 Cyg
Imaging Details
Variable Star:
V1193 Cyg

Other Designation:
GSC 3949-0797

RA / Dec:
20h 21m 11s /
+59° 36' 04"


Magnitude:
13.8 - 14.3 (p)

Period:
0.50376561 days

Variability:
EW

Comparison Star:
GSC 3949:0689

Check Star:
GSC 3949:1337


Date:
Aug 06, 2013
00:15:00 - 04:10:26 UT+3


Location:
Athens, Greece
(38.2997° N, 23.7430° E)


Equipment:
AP 305/f3.8 Riccardi-Honders
AP 1200GTO GEM
SBIG ST-10XME
SBIG CFW-10
SBIG LRGB filters


Integrations:
White :  107 x 120 sec
Dark :  010 x 120 sec
Flat :  ~23,000 ADU
Binning :  1x1

Temperatures:
Ambient : + 20.0 ° C
CCD Chip : - 12.5 ° C

Software:
CCDSoft V5.00.201
AIP4Win V2.4.0


Processing:
Reduction
Differential Photometry