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          713        290 
1993         1261        470 
1994         1604        591 
1995         2801        981 
1996         2814        997 
1997         2789        953 
1998        24447      10288 
1999        13271       5065 
2000        37295      15362 
2001        42776      16815 
2002        39908      16732 
2003        59186      24196 
2004        46175      17609 
2005       309369     139151 
2006       335755     149761 
2007       195613      60553 
2008       112518      32205 
2009        93437      26233 
2010       141669      37829 
2011       150872      41216 
2012       178527      39216 
2013       235379      59580 
2014       533705     131092 
2015       760200     198294 
2016       626889     162009 
2017       526927     143274 
2018       317764      89471 
2019       825797     201849 
2020       546322     138389 
2021       745163     174785 
2022       575330     164824 
2023       524912     150300 
2024       569701     163693 
2025       553940     156801 
2026       224227      45600