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          228         81 
1991          867        310 
1992          708        288 
1993         1261        470 
1994         1599        589 
1995         2797        980 
1996         2814        997 
1997         2789        953 
1998        24439      10285 
1999        13259       5062 
2000        37288      15359 
2001        42774      16814 
2002        39893      16726 
2003        59180      24194 
2004        46160      17605 
2005       309329     139138 
2006       335736     149756 
2007       195579      60544 
2008       112451      32186 
2009        93363      26211 
2010       141632      37818 
2011       150816      41201 
2012       178436      39193 
2013       235286      59554 
2014       533756     131113 
2015       759908     198227 
2016       626902     162009 
2017       526856     143252 
2018       315735      89134 
2019       824410     201743 
2020       546261     138376 
2021       744887     174714 
2022       575054     164750 
2023       524680     150235 
2024       569530     163647 
2025       553739     156746 
2026       224979      45799