Visual Discovery of SN 1995ad in NGC 2139.

(Robert Evans)

Amateur astronomers are used to the complaint: that there has been a lot of cloudy weather lately. While this has been true for me in the last few months, that is not the only reason why it has been such a long time since the last occasion that a SN was discovered with my backyard 41cm telescope. In 1994 there were several amateur discoveries of Sne, either visually or using a CCD as a detector. A few of these were purely northern hemisphere objects, but of the ones that I could see it was the case that I simply did not look in the right place at the right time. I was happy for other people to be successful. Earlier in 1995 I found two Sne using the forty-inch telescope belonging to the Australian National University.This seemed to accentuate in my mind that it was two years and five month since the last discovery was made with the backyard telescope, which is my normal instrument for searching. On the morning of 1995 Sept 29 (local time) I did not set the alarm clock, although I hoped to do at least a little observing. When I awoke there was only fifty minutes left before first light and it took the minutes to get dressed and get the telescope out of the shed onto the observing pad in the back lawn. I started observing galaxies in Canis Major, and lost a bit of time because there were several objects that I could not find. With ten minutes to go before first light I loked at NGC 2139 in Lepus and noticed a new star on the western side of the galaxy. Because my brain was not functioning well, it took several moments to dawn upon me that here was a new object, and I had to blink and stare hard to be sure I was not seeing things. The new star seemed to be brighter than magnitude 15 and was about 25 arc seconds west of the nucleus of the galaxy, and about five seconds south. Because such a short time was left before dawn, I kept on looking at other objects. Even so, I only logged 18 galaxies in forty minutes of observing. My reference pictures of NGC 2139 consisted of slides from the ESO 'B' Survey and CCD pictures from Vickers and Wassileff's Deep Space CCD Atlas, South. When I went inside to lok at these reference pictures, there was too much light to get any confirmation of the discovery in Eastern Australia. So I followed a procedure that is NOT generally recommended and phoned the Central Bureau in Boston with my information hoping that I would be able to ring again later after I had arranged for the confirmation locally or through the 'Nova-Net'. However, because I was confident about the reality of this discovery, Dr. Brian Marsden offered to notify his network of people who were interested in supernovae in order to get the needed spectral confirmation. Subsequent events showed the wisdom of this course of action. In response to this Dr. Stefano Benetti obtained the spectra at the ESO in Chile twelve hours after the first sighting.The spectra showed that the Sne was of type II and was around maximum light. My previous negative observation of this galaxy had been on 1995 August 25. Rob NcNaught was able to get a CCD picture of the galaxy and supernova , and an exact position with the forty-inch telescope through cirrus clouds which had been thicker for most of the night and had stopped his scheduled observing. Rain and cloud stopped all observing for the next four nights. Because of this any additional local confirmation would not have been possible.