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The Journal of the British Astronomical Association, 2015 October

Volume 125, Number 5

The controversial correspondence of Edwin Holmes, daytime collimation of a Schmidt-Cassegrain telescope, and details of the Mercury transit of 2016 May 9. Log in or join the BAA today to view this journal online. A full list of contents is also available. Selected highlights from this Journal:

Notes and News

From the President
Hazel McGee
Aurora Section
Ken Kennedy

Refereed Papers

The controversial pen of Edwin Holmes
Edwin Alfred Holmes (1839-1919) is best remembered for his discovery of a bright comet in 1892, now known as Comet 17P/Holmes. An amateur astronomer and authority on optics, he was an original member of the BAA and contributed to its Journal and meetings for many years. As a prolific writer of letters to English Mechanic, he developed a reputation for his controversial and acerbic penmanship.
Jeremy Shears
Spectral changes in AC Herculis during its rise to a maximum in 2014 July
Four low resolution (R~1000) spectra were obtained of the RV Tauri-type variable AC Her during its rise from a deep minimum in July 2014. These show changes in spectral type and Balmer line equivalent width as the star brightened, consistent with earlier observations.
David Boyd
Kitchen table collimation of a Cassegrain-type reflector
A method of daytime collimation of a Cassegrain-type reflecting telescope is described, which uses a circular target aligned on the optical axis of the primary mirror. Basic construction details are given for making a suitable target and a procedure is outlined for collimating both Schmidt–Cassegrain and Ritchey–Chrétien telescopes.
Russell Slater
The eclipsing binary HS0705+6700 binary and the search for circumbinary objects
HS0705+6700 (also identified as V470 Cam) is a short period (2.3 h) post-common envelope detached eclipsing sdB binary system which exhibits transit time variations (TTVs) of a cyclical nature. We report a further 25 timings of light minima and show that our new TTVs support and extend this cyclical pattern to 1.6 periods. We examine possible causes of the observed TTVs and confirm that the presence of a third, and possibly a fourth, body could provide an elegant explanation of these cyclical variations. However other non-circumbinary mechanisms, e.g. Applegate magnetic dynamo effects, will remain possible contenders until sufficient data has been accumulated to demonstrate that the periodicity of the TTVs is time independent. A further 27 eclipse timings recorded between 2014 October and 2015 April are reported in the Addendum. These new timings occurred 0.00012 days (~10s) later than anticipated by our circumbinary model. Two possible explanations are offered.
D. Pulley, G. Faillace, D. Smith, A. Watkins & C. Owen