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         1267        472 
1994         1616        595 
1995         2840        994 
1996         2847       1008 
1997         2861        977 
1998        24580      10334 
1999        13426       5122 
2000        37681      15540 
2001        43234      17014 
2002        40416      16949 
2003        60050      24542 
2004        46830      17871 
2005       311881     140122 
2006       337973     150578 
2007       197877      61159 
2008       115374      32976 
2009        96636      27096 
2010       147165      39199 
2011       155913      42580 
2012       184009      40707 
2013       241964      61415 
2014       541423     132927 
2015       771764     201343 
2016       623897     161040 
2017       539571     146600 
2018       328766      92482 
2019       837967     204749 
2020       570349     144424 
2021       779840     183732 
2022       590605     169149 
2023       537262     153757 
2024       587348     168794 
2025       603936     172593 
2026        52229      14556