The frequency of appearance of bright naked eye comets since 1750

It is a typical lament of the astronomers of today that there has been a dearth of bright comets in the 20th century and, particularly in its latter half. Many go on to point out the large number of very bright comets that were observed in the 18th and 19th century to reinforce the unfavourable comparison with modern times. Analysis of bright naked eye comet apparitions since 1750 demonstrates that there was a superavit of very bright comets in the second half of the last century. The second half of the twentieth century has shown exactly the average of one bright naked eye comet per 2.5 years that has been seen over two and a half centuries. The probable cause of theapparent lack of bright comets is the great increase in light pollution and the shift of population to the big cities. The observed statistics for the appearance of bright comets show no obvious evidence of perturbations of the Kuiper Belt by Planet X.     

Type Ia supernovae observed at La Palma Observatory: Looking for differences within a recent sample

A sample of recent type Ia supernovae has been observed from La Palma. Spectra of there supernovae were taken at two different phases: around maximum and between one and two months after maximum. We present here our observations and discuss the existence of intrinsic differences within the sample.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

On the 2001 Splitting of the Nucleus of 51P/Harrington

The nucleus of 51P/Harrington suffered a majorsplitting event in Autumn 2001discovered by amateur José Manteca.The light curve and separation of thefragments is examined based on data fromthe observers collaborating in the Spanishlanguage ``Cometas_Obs' mailing list, includinga number of pre-announcement observations. Thereis some uncertainty in the epoch of the initiationof the split. Some evidence favours an earlierinitiation than September 2001.     

Comet Hale-Bopp (1995 O1)

Considerable interest has been raised by the discovery of Comet Hale-Bopp (1995 O1) and the possibility that it might become a very bright object in Spring 1997. The evidence to support either of the conflicting hypothesis (an intrinsically bright comet or a faint comet in a very large outburst) is too limited to reach solid conclusions and may remain so for some months yet. The pre-discovery observations encountered to date provide some limits to photometric models and suggest that the comet may be intrinsically bright, but do not yet permit a firm discrimination, even between extreme scenarios, due to the enormous extrapolation that must be made from the heliocentric distance at discovery, to that of perihelion.     

The Leonid outburst of 1996

There is strong anticipation that the Leonid meteor shower could produce storm-level activity in 1998 and/or 1999. The well-documented Leonid outburst in 1996 and the more poorly observed one in 1994 have been taken by many observers to imply that a storm is imminent, This article explores the possible relationship between the 1996 outburst in activity and possible Leonid storms. The curve of activity is found to be much closer to that of normal activity, although with greater hourly rates, than it is to the very brief, steeply rising activity curve of a storm. It is probable that the 1996 outburst is thus completely unrelated to any future storm which may appear.     

Accuracy of four-node standard finite element

In this note the accuracy of the elastic standard 4-node plane-strain finite element is investigated by comparing numerically calculated eigenvalues of the element stiffness matrix to those according to higher-order algebraic approximations. From this study it may be concluded that the ‘hourglass’ eigenmodes are the only inaccurate ones. For selective reduced numerical integration the hourglass eigenvalues may be expected to be of the order of 1/2 to 2/3 of the analytical values.     

Visible and near-infrared monitoring of 3C 279 in 1988–1989

We present near-infrared monitoring taken with the 1.5 m Carlos Sánchez Telescope in Tenerife and CCD photometry taken with the Jacobus Kapteyn Telescope in La Palma of the 1988 outburst of 3C 279. This is combined with archival data to examine the behaviour of the light curve fromB toK.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain.     

A powerful new infrared array camera for the NASA Infrared Telescope Facility

We have just finished building a 1.0–5.5 m infrared array camera for the NASA Infrared Telescope Facility based upon the SBRC 256×256 InSb array. After a brief overview of the capabilities of the camera (named NSFCAM), we present some of the first images obtained with this new camera, including results obtained with our realtime shift & add speckle imaging mode.