TypeType II SupernovaClick for lightcurveLines of hydrogen and other elements are apparent in their spectra. The expanding envelope consists mainly of H and He. Light curves show greater diversity than those of type I supernovae. Usually after 40-100 days since maximum light, the rate of fading is 0.1 magnitudes per day.AAVSO Special Notice 421, 22 September 2016SN 2016gkg (announced as AT2016gkg) was discovered by Victor Buso (Rosario, Argentina) on 20 September 2016 at CCD magnitude (clear filter) 17.6 +/-0.5, rising to 14.5 +/-0.02 on Sep. 21.1398. His discovery was reported to the Transient Name Server by Sebastian Otero (Buenos Aires, Argentina). It was confirmed by ASAS-SN on Sep. 21.29 UT (B. Nicholls (Mt. Vernon Obs., New Zealand) et al., ATel #9521) and by ATLAS on Sep. 20.54 UT (J. Tonry (IfA, University of Hawaii) et al., ATel #9526).SN 2016gkg was spectroscopically confirmed as a Type-II supernova by S. W. Jha (Rutgers), V. van Wyk, and P. Vaisanen (SALT/SAAO) from observations made on 2016 September 21.9 UT (ATel #9528).Its optical behavior has been very unusual, with more than a magnitude decline in 24-48 hours, which is highly atypical for a Type-II supernova. It is for this reason that observations are requested as the supernova evolves. The most recent magnitude available is 15.73 V +/- 0.05 on 2016 Sep. 22.3 UT, using ASAS-SN data (Ping Che (KIAA-PKU) et al., ATel #9529).V observations are requested; other bands may be added as time and inclination permit. As this supernova appears to be changing so quickly, multiple observations per night would be valuable.