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         1827        668 
1995         3324       1156 
1996         3559       1250 
1997         2306        787 
1998        23162       9770 
1999        14473       5549 
2000        40118      16637 
2001        40955      15961 
2002        32079      14350 
2003        60213      24996 
2004        47513      18225 
2005        83635      25729 
2006       108063      34603 
2007       198773      61161 
2008       120156      34263 
2009        98560      27733 
2010       113777      31671 
2011       168724      46714 
2012       158541      43887 
2013       237260      67471 
2014       580376     149064 
2015       701963     186153 
2016       676585     175658 
2017       575894     155710 
2018       375022     105208 
2019       901343     220450 
2020       656424     167394 
2021       869967     207415 
2022       644827     184615 
2023       591970     169433 
2024       405284     117999