Taken 24th November with the Alan Young Telescope
This image shows a comparison of the variable star SS Cyg to show the difference between its minimum and maximum brightness.
Variable Star Observing
At the start of the 19th century very few variable stars were known, certainly less than a few dozen. Nowadays, the ‘Bible’ for all types of variable star (the General Catalogue of Variable Stars) lists over 40,000 variables!
Even simple observation of these stars can yield information about their mass, radius, luminosity and evolution. And what’s more it can be done with the simplest of equipment. We usually observe variable stars by measuring their variations over time. These variations take the form of changes in brightness (magnitude) and are viewed as a light-curve (magnitude against time).
Why observe variable stars?
Variable stars can tell us much about stellar evolution and ultimately, the fate of our own Sun. Professional astronomers need amateur observations as there are just too many variable stars for them to follow. Their telescopes are often too large, and observing time on them is scarce. This is one of the few areas where an amateur can make a real contribution to science. So at CADSAS we contribute data to the Variable Star Section (VSS) of the British Astronomical Association (BAA) for a wide selection of variable stars.
What are variable stars?
Three main types of variable star are observed by the VSS: Pulsating, Eclipsing and Eruptive.
Pulsating stars (Miras, semi-regulars [SRs] etc.) The variations are caused by the star physically pulsating, like a balloon blowing up and down, but only the outer layers are involved. Periods range from hours to years, depending on the type. The variation in brightness can be from about 0.5 magnitudes to over 10.
Eclipsing binary stars (EBs) The variations are caused by two stars in our line of sight that physically revolve around each other. Periods range from hours to many years. Some may be seen to undergo an entire eclipse in a single night.
Eruptive stars (CVs, novae and supernovae) These stars show sudden increases in magnitude known as ‘outbursts’, sometimes quite gentle and relatively frequent, and sometimes the gigantic explosions we call supernovae. Many CVs (‘cataclysmic variables’) are actually binary stars in which the eruptions are due to an exchange of material from one star to the other, often via an accretion disc. There are many subtypes of CVs and form one of the most interesting areas for observing.
Attached is an image captured on the remote telescope SLOOH of the supernova (SN2023ixf) (arrowed) located in one of the arms of Messier M101 (Pinwheel Galaxy).
Details : 11 June @ 22.39 UT using Canary One CDK20 60 seconds exposure by Ivan Walton.
NGC 4565 (Caldwell 38) a spiral galaxy in Coma Berenices, known as the Needle Galaxy taken on 20 March 2023 at 00:11:23 UTC with the COAST (Tenerife) CDK17 and FLI Proline KAF-09000 CCD with an exposure of 120 seconds through a clear filter.
An image of NEA (Near Earth Asteroid) 2023 DZ2 affectionately known as ‘Dizzy’. Taken at 00:38 UT from the remote telescope CDK20 in the Canaries.
Two adjacent time exposures showing movement left of centre.
The Eagle Nebula, M16 (NGC 6611) in the constellation of Serpens, taken on 28 February 2023 at 05:06 UT with a LRGB – 50,20,20,20 seconds exposure using a CDK 17 scope and FLI PL 16803 CCD camera at SLOOH in the Canaries. By Ivan Walton.
A 50 secs exposure taken on 18 December 2022 at 22:06 UT at SLOOH in the Canaries with a BCDK 17 telescope and FLI PL16803 CCD camera. By Ivan Walton.
NGC 4372 (Caldwell 108) a globular cluster in the constellation of Musca, taken on 24 January 2023 at 03:10 UT with a 50 seconds exposure using a Celestron 14 with SBIG STL-11000M camera at SLOOH (Chile). By Ivan Walton.
QS Ori, with a calculated magnitude of 12.5V. Captured on 23rd Februrary 2023 with the Alan Young Telescope.