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        43242      17017 
2002        40434      16957 
2003        60116      24568 
2004        46855      17881 
2005       311965     140151 
2006       338111     150630 
2007       198010      61195 
2008       115533      33018 
2009        96892      27168 
2010       147293      39233 
2011       156285      42682 
2012       184347      40799 
2013       242542      61574 
2014       543804     133482 
2015       780578     203331 
2016       624881     161250 
2017       541258     147011 
2018       329566      92695 
2019       839722     205203 
2020       573407     145255 
2021       783741     184804 
2022       594555     170240 
2023       539104     154258 
2024       589721     169467 
2025       607021     173445 
2026        49396      13584