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          719        292 
1993         1273        474 
1994         1622        597 
1995         2848        997 
1996         2865       1014 
1997         2870        980 
1998        24598      10340 
1999        13441       5127 
2000        37730      15561 
2001        43252      17022 
2002        40454      16965 
2003        60138      24577 
2004        46898      17896 
2005       312039     140177 
2006       338208     150665 
2007       198130      61228 
2008       115689      33061 
2009        97081      27219 
2010       147409      39264 
2011       156517      42745 
2012       184628      40873 
2013       242865      61663 
2014       545024     133769 
2015       784071     204021 
2016       625636     161428 
2017       541725     147098 
2018       330043      92831 
2019       840805     205438 
2020       574168     145470 
2021       784899     185131 
2022       595596     170536 
2023       539517     154371 
2024       590818     169782 
2025       610881     174557 
2026        16410       4765