Year Observations     Objects
1950            2          1 
1951            6          3 
1953            4          2 
1954            2          1 
1955            4          2 
1956            2          1 
1960            6          3 
1974            2          1 
1975            2          1 
1976            8          4 
1977            2          1 
1978            8          3 
1981            4          2 
1982           12          6 
1983            8          4 
1984            2          1 
1985            8          4 
1986            4          2 
1987            2          1 
1988           38         18 
1990           32         14 
1991          492        186 
1992          770        310 
1993         1356        504 
1994         1755        643 
1995         3321       1155 
1996         3521       1237 
1997         2300        785 
1998        23156       9767 
1999        13533       5235 
2000        40110      16634 
2001        40938      15954 
2002        32070      14346 
2003        60186      24986 
2004        47497      18219 
2005        83565      25706 
2006       107935      34566 
2007       198441      61072 
2008       119795      34168 
2009        98409      27693 
2010       113489      31595 
2011       168257      46588 
2012       158359      43837 
2013       236389      67234 
2014       579631     148875 
2015       700875     185853 
2016       676216     175537 
2017       576248     155679 
2018       373795     104871 
2019       899806     220029 
2020       650926     166001 
2021       868990     207200 
2022       644203     184438 
2023       587755     168195 
2024       438314     127662