Variable Stars 2018
Unless stated otherwise all variable star charts or phase diagrams were constructed from data taken with a William Optics Megrez 90 telescope with a 0.8x focal reducer and with an Atik 460EX CCD camera through a Johnson V photometric filter. Exposures are chosen to avoid saturating the variable star or any of the comparison stars.
The target star is located using SGPro software with plate solving. The data is analysed with the free software Muniwin and the final chart produced in Excel. To produce a phase diagram I have used Peranso.
Finder charts have usually been obtained from the AAVSO website together with details of suitable comparison stars. All results have been submitted to the BAA and AAVSO.
Eclipsing Binary star AB Cassiopeia
The chosen exposure time for these readings was 10s. The gap in the readings is where I performed a meridian flip after which the gear did not behave for a while.
This chart shows the primary eclipse.
Eclipsing Binary Star AD Andromeda
The chosen exposure time for these readings was 20s. There was a near full Moon and the target star was of lowish altitude which may explain the scatter of the readings. Using the program Peranso with these and readings taken last year I determined the period of this binary to be 0.9862 days which agrees with the value given by aavso.
Strangely the time of the primary minimum was about an hour different from the Krakow prediction of 22:54 UT. On further investigation it turns out that the Krakow database predictions for this star is based on 15 year old data and an hours difference now could be produced with just one second in the time period. This data has been submitted to them for possible updating of their predictions.
Pulsating variable star YZ Boo. All of my previous variable star measurements have been of eclipsing binary stars where the change in brightness is due to one star coming in front of the other. YZ Boo is a single star that pulsates radially and so causing a brightness fluctuation.
The process behind this is essentially the same as in Cepheid variables. Main sequence stars are in equilibrium. There is an outward force due to the internal pressure which depends on the temperature and an inward force due to gravity. The driving mechanism behind "self-
These results were obtained with my Megrez 90 and Atik 460EX CCD camera. Multiple exposures of 20s were taken with the aid of SGPro and the data analysed with the free software Muniwin.
Pulsating variable star YZ Boo.