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         3321       1155 
1996         3559       1250 
1997         2306        787 
1998        23157       9768 
1999        14473       5549 
2000        40118      16637 
2001        40952      15960 
2002        32079      14350 
2003        60208      24994 
2004        47510      18224 
2005        83625      25726 
2006       108055      34601 
2007       198738      61152 
2008       120128      34256 
2009        98540      27728 
2010       113745      31663 
2011       168661      46697 
2012       158512      43879 
2013       237160      67443 
2014       580293     149041 
2015       701852     186121 
2016       676826     175686 
2017       575951     155706 
2018       374901     105174 
2019       901228     220410 
2020       651312     166179 
2021       869877     207389 
2022       644746     184591 
2023       592326     169479 
2024       418090     121761