Variable Stars


The Society has a long history of variable star observing from its formation and members have contributed several thousand observations to the BAA Variable Star Section.
Both experienced observers and newcomers are encouraged to participate in variable star observing. Since the late 1980’s though, photoelectric photometry has been the prominent form of observing with the result that the number of visual observations has declined, this has since been superseded by CCD photometry in the mid 90’s and this is now the main tool for photometric studies.


Variable stars are labelled after the constellation that they reside in, in order of discovery, the first variable in a constellation is given the designation ‘R’ and subsequent variables are labelled as follows…
R, S, T, U, V, W, X, Y, Z however this didn’t prove to be enough! So the labelling continues with…
SR, SS, and on until you reach ZZ, this also was inadequate, so the labelling continues from
AA through to QZ giving a total of 334 variables in any constellation, after this variables are numbed and have a preceding ‘V’, starting with V335 in recognition of the 334 variables before it.

Types of Variable

There are two broad categories of variable star, intrinsic and extrinsic variables.


Vary due to the internal nature of the star, for example a star that is pulsating.


Vary due to external influences, for example binary stars eclipsing each other.

Further Reading

BAA Variable Star Section | AAVSO | Wikipedia




First Light with a new CCD on RS Boo

A phase curve from Martin Crow’s first four sets of  test observations using the pulsating star RS Boo as a target. Period 0.37733days. Acquired with 235mm SCT @ f6.3 and SX694 camera and sxcon software . Processed with AIJ and VSS...


HD 209458 HD 209458 is an 8th magnitude star in the constellation Pegasus. It is very similar to our Sun, and it is classified as a yellow dwarf (spectral class G0 V). The star is easily visible With good binoculars or small telescope. Essential Details Star Designation(s) TYC 3198-1634-1 (TYC is also known as the Guide Star Catalog GSC) Position J2000 RA:22h 03m...