Summer maximum of chi Cyg

Forums Variable Stars Summer maximum of chi Cyg

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    Gary Poyner

    Members might like to know that the Mira type Variable Star chi Cygni is now around magnitude 9.0 (May 25), and is becoming visible in small binoculars as it heads towards a late June early July maximum.

    Maximum brightness can vary by as much as 2 magnitudes (3.5-5.5), so it’s impossible to say at this time just how bright chi Cyg will be at the end of June. The maximum of 2013 turned out to be very bright (3.8 mean) with the variable visible with the naked eye above magnitude 5 for over two months. DSLR users will notice a much brighter magnitude on their images as chi Cyg brightens, unless a V filter is employed.

    chi Cyg has a period of 408d, so the variations are quite slow. One observation every 7-10 days is adequate at this time, but can rise to 5-7 days as it approaches maximum. Even if you don’t want to make measurements of it’s brightness, it’s fascinating (and fun) to watch the star brighten in binoculars and hopefully pop into naked eye view in mid-late June, then slowly disappear again a couple of months later.

    chi Cyg has been observed by members of the BAAVSS since 1891, and the whole light curve can be viewed on the VSS web page – Charts can also be downloaded if you fancy having a go at estimating it’s brightness. If you do then please do let us know how you get on, and perhaps you may even consider reporting your observations to the section database!

    Good luck,

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