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          471        179 
1992          749        303 
1993         1308        487 
1994         1686        619 
1995         3108       1084 
1996         2991       1057 
1997         1917        661 
1998        22337       9439 
1999        13614       5225 
2000        38846      16066 
2001        39628      15401 
2002        31031      13903 
2003        58199      24209 
2004        46720      17929 
2005        82109      25268 
2006       105826      33948 
2007       193434      59727 
2008       115164      32912 
2009        94876      26727 
2010       114115      31681 
2011       161420      44752 
2012       152698      42300 
2013       225306      64169 
2014       568950     144988 
2015       797875     208945 
2016       664174     172245 
2017       560233     151511 
2018       358209     100596 
2019       875192     213696 
2020       629886     160334 
2021       847456     201639 
2022       631479     180756 
2023       569003     162610 
2024       634293     182619 
2025       126908      36104