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         2128        771 
1995         3351       1165 
1996         3564       1252 
1997         2320        791 
1998        23180       9776 
1999        14486       5554 
2000        40187      16667 
2001        41075      16007 
2002        32187      14395 
2003        60497      25105 
2004        47613      18262 
2005        84031      25850 
2006       108844      34829 
2007       200155      61531 
2008       121655      34666 
2009        99167      27899 
2010       114974      31988 
2011       170572      47218 
2012       159928      44262 
2013       241314      68559 
2014       583609     149900 
2015       706798     187496 
2016       678688     176214 
2017       578229     156329 
2018       379253     106366 
2019       906663     221986 
2020       655433     167396 
2021       873032     208214 
2022       656123     187655 
2023       600673     171550 
2024       328862      95403