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          512        193 
1992          936        367 
1993         1669        610 
1994         2329        840 
1995         4425       1527 
1996         3593       1262 
1997         2337        797 
1998        23319       9830 
1999        14594       5599 
2000        40643      16874 
2001        41663      16249 
2002        32795      14655 
2003        61735      25587 
2004        48507      18610 
2005        86626      26612 
2006       112132      35798 
2007       206776      63325 
2008       127631      36284 
2009       103919      29182 
2010       120628      33471 
2011       181657      50225 
2012       168640      46655 
2013       262446      74426 
2014       653208     166550 
2015       760077     201588 
2016       578959     154424 
2017       609219     162631 
2018       406761     114002 
2019       932734     227437 
2020       705638     181087 
2021       918095     220646 
2022       687243     196528 
2023       619139     178164 
2024       139938      40079