Year Observations     Objects
1950            2          1 
1951            6          3 
1953           14          8 
1954           12          5 
1955           12          6 
1956            8          4 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978           12          5 
1981           18          5 
1982           13          7 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990          213         76 
1991          856        306 
1992          656        270 
1993         1176        442 
1994         1481        553 
1995         2350        830 
1996         2614        928 
1997         2480        847 
1998        23904       8540 
1999        12798       4882 
2000        36244      14882 
2001        41357      16238 
2002        34910      14935 
2003        56786      23265 
2004        44739      17040 
2005       302555     136367 
2006       330214     147483 
2007       191450      59328 
2008       107355      30639 
2009        87727      24555 
2010       135479      36092 
2011       142217      38702 
2012       169828      36799 
2013       223561      56231 
2014       470206     116683 
2015       708131     185191 
2016       598496     154675 
2017       502483     136608 
2018       300175      84897 
2019       801373     196266 
2020       524924     133019 
2021       706339     165247 
2022       548699     157405 
2023       508332     145643 
2024       548192     157580 
2025       523105     148752 
2026       367981      87603