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         1581        580 
1994         2317        836 
1995         3368       1171 
1996         3576       1256 
1997         2326        793 
1998        23250       9803 
1999        14520       5567 
2000        40442      16781 
2001        43005      16675 
2002        32462      14510 
2003        61122      25342 
2004        47908      18374 
2005        85217      26202 
2006       110649      35359 
2007       203638      62466 
2008       124829      35535 
2009       101486      28524 
2010       118023      32785 
2011       176848      48908 
2012       164252      45418 
2013       254656      72030 
2014       604666     154823 
2015       730163     193628 
2016       713495     184292 
2017       601177     162188 
2018       395867     110923 
2019       928912     228032 
2020       684482     175355 
2021       893339     213823 
2022       663325     189724 
2023       602263     173405 
2024       243518      70520