Year Observations     Objects
1858            3          3 
1889            1          1 
1901            1          1 
1920            6          2 
1950            2          1 
1951            6          3 
1953           14          8 
1954           12          5 
1955           14          7 
1956            8          4 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978           12          5 
1981           18          5 
1982           13          7 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990          231         82 
1991          867        310 
1992          721        293 
1993         1280        477 
1994         1628        599 
1995         2881       1008 
1996         2886       1021 
1997         2927        999 
1998        24676      10371 
1999        13483       5143 
2000        37885      15630 
2001        43357      17069 
2002        40603      17029 
2003        60472      24710 
2004        47133      17979 
2005       312606     140389 
2006       338794     150915 
2007       198608      61360 
2008       116537      33294 
2009        97629      27363 
2010       147853      39378 
2011       157427      42990 
2012       185622      41147 
2013       244161      62015 
2014       561718     137630 
2015       811855     210047 
2016       632625     163108 
2017       545314     147716 
2018       332521      93468 
2019       844270     206274 
2020       580385     147044 
2021       791358     186878 
2022       600450     171900 
2023       542139     155136 
2024       597195     171601 
2025       589121     167979