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          532        200 
1992          936        367 
1993         1669        610 
1994         2333        842 
1995         4427       1528 
1996         3602       1265 
1997         2340        798 
1998        23334       9837 
1999        14618       5609 
2000        40747      16922 
2001        41818      16314 
2002        32971      14725 
2003        62025      25708 
2004        48695      18685 
2005        87065      26740 
2006       112770      35984 
2007       207792      63601 
2008       128731      36580 
2009       104643      29380 
2010       121607      33731 
2011       183241      50657 
2012       169880      46993 
2013       265034      75154 
2014       661047     168552 
2015       773271     204877 
2016       577796     154259 
2017       587564     157705 
2018       406760     114110 
2019       927196     226353 
2020       712879     182978 
2021       925492     222607 
2022       692667     198032 
2023       629226     181064 
2024        86968      25366