Michael J.I. Brown and R. L. Webster, PASA, 15 (2), 176
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Introduction
Since the discovery of 
(Jewitt and Luu 1993), a total of 60 large (
radius) but dim (
) objects have been found with orbits beyond Neptune (Marsden 1997). It is thought that these objects are members of a belt of objects beyond Neptune (the Kuiper belt) hypothesised by Edgeworth (1949) and Kuiper (1951).
Previous published surveys for Kuiper belt objects are summarised in Table 1. Successful surveys for Kuiper belt objects have covered a total area of 
near the ecliptic (Jewitt and Luu 1995, Williams et al. 1995, Irwin et al. 1995, Jewitt et al. 1996, Jewitt et al. 1998). The objects detected by ground-based searches have had magnitudes 
with the majority of objects having magnitudes 
. Several surveys have covered larger areas of sky to brighter limiting magnitudes but these surveys have not detected any Kuiper belt objects. The size and magnitude distribution of Kuiper belt objects brighter than 
is therefore not well constrained.
Table 1. Surveys for Kuiper Belt Objects
limit for Kowal (1989) is that given in Irwin et al. (1995). limit for Levison and Duncan (1990) is that given by Levison (private communication). Only 
of the Kuiper Belt objects at the magnitude limit of Jewitt et al. (1998) could be detected by that survey. A detailed discussion of previous surveys for Kuiper belt objects can be found in Brown (1997). Another 22 Kuiper Belt objects have been detected (Marsden 1997) by surveys that have not been published in peer reviewed journals. | Reference | limit | Area | Detections |
( ) | |||
| Tombaugh (1961) | 16.8 | 1530 | 0 |
| Kowal (1989) | 18.5 | 6400 | 0 |
| Luu and Jewitt (1988) | 19.5 | 297 | 0 |
| Irwin et al. (1995) | 20.0 | 50 | 0 |
| Levison and Duncan (1990) | 21.0 | 4.9 | 0 |
| This Paper | 21.0 | 12.0 | 0 |
| Williams et al. (1995) | 22.0 | 0.5 | 1 |
| Jewitt et al. (1998) | 22.5 | 51.5 | 13 |
| Jewitt et al. (1996) | 23.2 | 4.4 | 3 |
| Irwin et al. (1995) | 23.5 | 0.7 | 2 |
| Luu and Jewitt (1988) | 24.0 | 0.34 | 0 |
| Jewitt et al. (1996) | 24.2 | 3.9 | 12 |
| Jewitt and Luu (1995) | 24.8 | 1.2 | 7 |
| Cochran et al. (1995) | 28.6 | 0.0011 | 29? |
Ideally one would like to continue previously successful surveys until larger objects are detected. However, all the successful surveys so far have used 1.5m to 4m telescopes at good sites that are heavily used by other astronomers. In this search, the compromise solution was to use a 1m telescope with a large field of view. The disadvantage with using a smaller telescope is that the limiting magnitude is significantly brighter than that expected on a larger telescope.
While shallow surveys of large areas of sky have not detected Kuiper belt objects, several have detected objects in orbits between Jupiter and Neptune (Centaurs). Only 7 Centaurs have been detected which have well-determined orbits (Marsden 1997). Centaurs and Kuiper belt objects have a slow apparent motion compared to main-belt asteroids and they are often described as slow moving objects (SMOs).
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