Popular Astronomy

Share to Facebook Share to Twitter Stumble It More...

Guide to U Cephei

A circumpolar eclipsing variable with a deep (2.5 magnitude) eclipse.

Extreme brightness range 6.7 - 9.3
More typical range always the same
Period of variation 2.493 days
Frequency of observation Every 30 minutes during an eclipse
Observe using 50mm binoculars will suffice for most of the time, but larger binoculars may be required during the deepest part of the eclipse
Visibility Can be observed all year round (although there may be a spell during the spring and/or summer when no eclipses are falling during the hours of darkness)

The primary eclipse occurs when the fainter star in the system passes in front of the brighter star.

The eclipses are "flat-bottomed", indicating that a total eclipse is taking place.

The orbital period of U Cephei is approx 2.493 days. Hence, if you see an eclipse on a particular night, another will be visible at a similar time of night 5 nights later.

If eclipses are occurring on schedule, the eclipse would be centred on phase 0.

This light curve shows the phases as calculated using the GCVS elements.

Although most observations in 2015 have been from the brightening stage of the eclipse, this light curve does suggest that the eclipses were occurring considerably later than predicted by the GCVS elements - by about 5 hours.

The eclipses are much more in line with predictions when phases are calculated using the more recent SAC elements - and it is these elements that are used when eclipse predictions are published.









The following finder charts show the location of U Cephei. The first shows how you can 'star hop' to it starting from Polaris. You can follow its brightness changes by comparing its brightness with that of the labelled comparison stars on the second chart (which is approx 5 degress by 4 degrees). Bear in mind that in smaller binoculars, U Cep may become too faint to be seen when near minimum.