The Forty Inch Telescope Search

Originally, my applications for observing time on this telescope were made as part of an effort to support applications for funding to buy or build a large telescope dedicated to visual supernova hunting. For the first time an attempt was being made to show what actually could be done with a telescope of this size in the area of visual supernova hunting. But, naturally, other related purposes are served as well by this effort.

The forty-inch telescope belongs to the Australian National University, and has been used almost every night in recent years by professional astronomers for CCD work of one kind or another. It is thirty years old, and as a result does NOT have the latest computer methods for locating objects automatically. So, the business of locating objects is the most time-consuming part of the work.

Applications for observing time are treated according to their scientific merit, and, as many projects as possible are supported by the Time Allocation Committee. My project is the only amateur one on Siding Spring mountain, so far as I know, and is certainly the only "visual" project,

An analysis of our observations for 1995 show that we were allocated a total of 52 nights on this telescope, of which 19 were in the dark of the moon (12 had fine weather), 24 nights were in the "grey" moon (11.85 were fine), and nine had bright moonlight (of which 3.4 nights had fine weather). I asked for a total of sixty nights, all in the dark of the moon, and with a minimum of forty-eight being acceptable. All things considered, the observatory authorities have been very generous, especially when we remember the demand there is to use the telescope, and that observers do not have to pay for the use of the telescope.

These 52 nights yielded a total of 495 possible hours of observing, of which 207 hours were fine, and 28 more were very poor. With this time we made 5, 223 observations of various galaxies, ranging from bright nearby galaxies to faint and distant objects which taxed the powers of the telescope. Six different supernovae were seen, including two that were discovered with this telescope. (SN 1995G in NGC 1643, and SN 1995V in NGC 1087.)

As a point of interest, on one of the better nights, Tom Cragg was able to make a visual estimate of the variable star SU Tauri at Magrtitude 17.3, when it was at about thirty degrees elevation above the horizon. So, overhead we could, at times, have seen somewhat fainter than that.

This rate of making galaxy observations averages out at about 25 observations per hour.

By comparison, my 41cm telescope is much more easy to move about from one object to another. Assuming that one has memorized the positions of the galaxies for star-hopping, it is possible to observe from fifty up to one hundred and twenty galaxies per hour with the smaller telescope. If the locations of the galaxies have to be found from maps, however, the rate of observations would be much slower. The forty-inch has the advantage at that particular point.

From long experience I found that for five thousand observations with the 41cm telescopes I would normally see two or three supernovae, of which I might discover one. On the average, I have discovered two supernovae per year, arising from 10,000 to 13,000 galaxy observations per year, since 1981, and have seen a few other supernovae per year in the process. The competition for the discoveries is increasing steadily, of course.

Of the six supernovae seen with the forty-inch telescope during 1995, I saw four of them with the 41cm. Of the two supernovae which were discovered with the forty-inch, one was too faint to have been noticed with the 41cm, and I did not normally observe the galaxy in question with the 41cm because of its assumed great distance. Naturally, the supernova that was found with the 41cm was also observed with the forty-inch later on.

While six supernovae, only 5, 223 observations, and only a twelve-month observing period, provide VERY small statistics of dubious value, the only way to improve the quality of these statistics is to increase greatly the number of observations and the range of galaxies being covered regularly. Perhaps a glimpse of the great capacities of this telescope is already achieved, although this is much hampered by the slowness of operating the telescope.

Observations with the forty-inch telescope will hopefully continue through 1996, as my application is based upon a two-year plan. Then we will have to see what other suitable telescope, if any, is available for this type of searching.