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         1359        505 
1994         2277        822 
1995         3365       1170 
1996         3576       1256 
1997         2326        793 
1998        23240       9799 
1999        14517       5566 
2000        40428      16774 
2001        42986      16669 
2002        32431      14496 
2003        61070      25323 
2004        47872      18363 
2005        85054      26152 
2006       110498      35312 
2007       203375      62396 
2008       124605      35472 
2009       101140      28430 
2010       117763      32717 
2011       176301      48757 
2012       163906      45323 
2013       253665      71757 
2014       603797     154593 
2015       728760     193255 
2016       717867     185339 
2017       600191     161972 
2018       395147     110726 
2019       930006     228365 
2020       682609     174829 
2021       892101     213492 
2022       662569     189498 
2023       600916     173023 
2024       255425      74004