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          716        291 
1993         1264        471 
1994         1616        595 
1995         2825        989 
1996         2832       1003 
1997         2831        967 
1998        24510      10310 
1999        13353       5096 
2000        37519      15464 
2001        43047      16931 
2002        40218      16862 
2003        59386      24293 
2004        46482      17734 
2005       310676     139648 
2006       336995     150231 
2007       196593      60805 
2008       114179      32653 
2009        95406      26766 
2010       145393      38754 
2011       153195      41850 
2012       181476      40014 
2013       239082      60609 
2014       534590     131155 
2015       765241     199603 
2016       618703     159701 
2017       531779     144525 
2018       323695      91092 
2019       830166     202823 
2020       556587     140989 
2021       760531     178894 
2022       583618     167187 
2023       531682     152220 
2024       577747     166019 
2025       570140     162842 
2026        81525      22576