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         1273        474 
1994         1616        595 
1995         2848        997 
1996         2850       1009 
1997         2870        980 
1998        24589      10337 
1999        13441       5127 
2000        37715      15554 
2001        43244      17018 
2002        40434      16957 
2003        60116      24568 
2004        46855      17881 
2005       311970     140153 
2006       338118     150632 
2007       198018      61197 
2008       115548      33022 
2009        96898      27170 
2010       147308      39237 
2011       156293      42684 
2012       184348      40799 
2013       242558      61579 
2014       543972     133516 
2015       780738     203370 
2016       624861     161234 
2017       541400     147036 
2018       329592      92703 
2019       839826     205226 
2020       573469     145272 
2021       783830     184830 
2022       594637     170264 
2023       539126     154264 
2024       589787     169486 
2025       607302     173528 
2026        45758      12575