Year Observations     Objects
1950            2          1 
1951            6          3 
1953            4          2 
1954            2          1 
1955            4          2 
1956            2          1 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978            8          3 
1981            4          2 
1982           12          6 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990           32         14 
1991          492        186 
1992          770        310 
1993         1356        504 
1994         1752        642 
1995         3318       1154 
1996         3425       1204 
1997         2291        783 
1998        23133       9758 
1999        14447       5538 
2000        40065      16614 
2001        40919      15942 
2002        32701      14551 
2003        60085      24949 
2004        47434      18197 
2005        83419      25663 
2006       107729      34504 
2007       197970      60947 
2008       119434      34069 
2009        98136      27620 
2010       113158      31511 
2011       167649      46426 
2012       157903      43719 
2013       235309      66934 
2014       577506     147356 
2015       698536     184372 
2016       673890     174492 
2017       575512     155430 
2018       372659     104560 
2019       897981     219531 
2020       649173     165582 
2021       867879     206922 
2022       643193     184153 
2023       587216     168095 
2024       449983     131171