TypeRecurrent novae, Eclipsing binary systemClick for lightcurveRecurrent novae differ from typical novae by the fact that two or more outbursts (instead of a single one) separated by 10-80 years have been observed.Eclipsing binary systems are binary systems with orbital planes so close to the observer's line of sight (the inclination of the orbital plane to the plane orthogonal to the line of sight is close to 90 deg.) that the components periodically eclipse each other. Consequently, the observer finds changes of the apparent combined brightness of the system with the period coincident with that of the components' orbital motion.AAVSO Alert Notice 558, 19 October 2016CI Aql monitoring needed to support HST observationsDr. Edward Sion (Villanova University) has requested AAVSO observers' assistance in monitoring the recurrent nova CI Aql in support of observations with the Hubble Space Telescope Cosmic Origins Spectrograph scheduled for October 31 - November 2, 2016, and November 3 - November 5, 2016. These observations are part of a study on short orbital period recurrent novae as Supernovae Type Ia progenitors.It is essential to know 24 hours prior to the HST COS observations that CI Aql is not in outburst, in order to protect the instrumentation. Observers are asked to keep an eye on CI Aql with nightly snapshot images (V preferred) from now until November 12, and to report their observations promptly. It will be especially important to know the brightness of CI Aql each night for October28 through November 7 UT. Visual observations are welcome.CI Aql (Nova Aql 1917) has had recurrent outbursts in 1941 and 2000, brightening to V~8.5. At minimum it is V~16-16.5 or fainter.