28 April - 18 May 1979
The Astronomer Early Warning Circular No 35 alerted members of OASI to the discovery of a supernova about 130 arcsec SE of the nucleus of the galaxy M100 (NGC4321). The discovery was made by visually by Gus Johnson, an amateur astronomer from Maryland, on 19 April 1979, only the third supernova ever to be discovered in this way. (Usually, such objects are found by detecting changes in the brightness of objects on photographic plates, or detecting an object on a plate where there was none previously.) The International Ultra-Violet Explorer (IUE) satellite has been turned towards the supernova to record the first ultra-violet spectrum of a supernova recorded from space.
At 22:30 UT on 28 April, Mike Barriskill and I observed the supernova with the Orwell Park 26 cm refractor. The object was clearly visible and Mike estimated it to be approximately magnitude 12 (no comparison stars had been identified at this stage). I sketched the star field below, and have appended the magnitudes of the comparison stars listed subsequently in The Astronomer Circular No 36. Due to luck with the weather and Mike's skill in using the Orwell Park refractor, by mid-May several members of OASI had seen the supernova. On 18 May, using the comparison stars suggested in Circular No 36, Mike together with other observers estimated the magnitude of the supernova as 13.