2012 programme

Sat 7th
16:30-17:00
TBA

TW Crucis — Piquing my Interest as a Beginner in CCD Photometry

David J. W. Moriarty

AAQ, VSS

Having bought a CCD camera for variable star photometry, I tried firstly a couple of targets listed in the VSS website, but saw no change. As a check on my techniques and ability to locate targets in dense star fields, I wanted something that would show a change within a few hours. TW Crucis, a short period (9.3 h) contact eclipsing binary system, was observed 8 times between 2011-05-05 and 2011-07-04, with minima seen on each occasion. The times differed from the published values; e.g. Observed – Calculated of 0.22 for GCVS elements. The primary and secondary minima were reported to be the same depth, but in fact my data showed that the primary was 0.05 magnitudes deeper. A phase plot of my data in the Vstar programme indicated that the period was 0.388143. It is possible that the period and the depths of primary and secondary minima have changed in the time since discovery. My interest in eclipsing binaries has definitely been excited by watching the eclipses of TW Crucis each time I did a run on it!

University Education: Bachelor of Agricultural Science (Hons), Adelaide 1966. Doctor of Philosophy, Adelaide, 1970 (Agricultural Biochemistry). Doctor of Science, The University of Adelaide, 1991 (for research on microbial ecology).
Honorary Professor, The University of Queensland 1997 – 2013
Member of the Astronomical Society of South Australia ca. 1955 – 1969.
Now retired and currently an active member of the AAQ, VSS and AAVSO.