Papers – Page 17 – British Astronomical Association

Saturn in the 2008/2009 apparition: Part II

Part I of this report described the observations of Saturn made by Saturn Section members during the 2008/2009 apparition. Part II presents observations of a number of satellite and shadow transits and Titan eclipses that occurred during the apparition.

New measurements and analysis of the β Cephei star V909 Cassiopeiae

V909 Cas is a little-studied example of a β (Beta) Cep pulsating variable star, located in the OB association Cas OB8 in the Perseus spiral arm of the Milky Way. Photometric observations in 2016-’17 provided thirty new times of pulsation extrema and enabled its mean pulsation period to be determined as 0.2067798(1)d. From spectroscopic observations we determined its interstellar extinction and absolute magnitude and luminosity, and located it with other β Cep stars in the OB instability region of the H-R diagram.

The 2012 solar transit of Venus

Results from the 2012 June solar transit of Venus are illustrated and discussed, and make an interesting comparison with our recent report on the 2016 transit of Mercury. As in previous years, observers were able to time the contacts, to see the ‘Black Drop’ effect (caused by inadequate resolution, but often enhanced by turbulence) and to record the ring of light around the unilluminated limb at both ingress and egress. This will be the last transit of Venus until 2117 Dec 11, unless we include the event of 2020 Jun 3, when the planet will be silhouetted against the solar corona.

The opposition of Mars, 2010: Part II

In Part II we discuss white clouds and the polar regions. The equatorial cloud band (ECB) was well observed from Ls= 001° onward. The behaviour of the orographic clouds over the great volcanoes was seasonally normal, in the absence of any large dust disturbance. We saw the Tharsis orographics from Ls= 011°, and the Olympus Mons orographic from Ls= 019°. As with the ECB, observations did not continue late enough to establish their seasonal decline. The 2009-’10 N. polar cap recession was followed in detail nearly as far as the summer remnant stage.

Visual measurements of the proper motions of 61 Cygni & Groombridge 1830 using an undriven 10-inch Dobsonian telescope

Results of visual measurements of the proper motions of 61 Cygni and Groombridge 1830, using an undriven 10-inch (250mm) Dobsonian telescope and an astrometric eyepiece, are presented. It is shown that reasonably accurate measurements of the proper motions of these stars can be made visually, using simple equipment, over a period of time that is less than two years.

The brighter comets of 2012

This report describes and analyses the observations of the brighter or more interesting comets discovered or at perihelion during 2012, concentrating on those with visual observations. Magnitude parameters are given for all comets with observations. Any evolution in the magnitude parameters of those periodic comets with multiple returns is discussed. Additional information on the comets discussed here and on other comets seen or at perihelion during the year may be found on the Section visual observations web pages.

Saturn in the 2008/2009 apparition: Part I

This report describes the observations of Saturn made by Saturn Section members during the 2008/2009 apparition. During this apparition, the rings were edge-on to the Sun and Earth on 2009 Aug 11 and Sep 4 respectively

A previously unreported naked-eye sunspot observation: 1604 November

Evidence is presented of a previously unreported naked-eye sunspot observation in 1604. A report from a 17th century Hungarian history is analysed and possible alternative interpretations are discussed. Further evidence of high solar activity at the time is briefly examined.

RZ Cas lightcurve and orbital period variations

A binary star model for RZ Cas is fitted to a set of high quality electronic magnitude observations of recent minima, deriving in the process some of the parameters of the system. This lightcurve is then fitted to raw observational data from the BAA, AAVSO, AFOEV and VSOLJ in order to determine the times of minimum. These observed times of minimum supplemented by data from the Lichtenknecker database are then compared to expected times and are shown to be consistent with several significant long-term changes in the period.

The opposition of Mars, 2010: Part I

This report summarises over 8,000 observations by 149 observers between 2009 March and 2010 September, covering martian northern late autumn to winter, spring and early summer (Ls= 232-156°). Part I discusses dust storms and albedo features.