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         1755        643 
1995         3321       1155 
1996         3559       1250 
1997         2306        787 
1998        23155       9767 
1999        14470       5548 
2000        40116      16636 
2001        40950      15959 
2002        32077      14349 
2003        60205      24993 
2004        47510      18224 
2005        83618      25723 
2006       108025      34591 
2007       198671      61134 
2008       120054      34236 
2009        98518      27722 
2010       113723      31657 
2011       168551      46667 
2012       158503      43876 
2013       237025      67406 
2014       580209     149020 
2015       701672     186071 
2016       677049     175710 
2017       576099     155714 
2018       374682     105112 
2019       901041     220358 
2020       651193     166139 
2021       869623     207346 
2022       644614     184555 
2023       592213     169446 
2024       421653     122797