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          767        309 
1993         1356        504 
1994         1746        640 
1995         3291       1145 
1996         3232       1138 
1997         2288        782 
1998        23088       9741 
1999        14416       5526 
2000        39970      16572 
2001        40778      15884 
2002        32301      14406 
2003        59790      24834 
2004        47301      18149 
2005        83033      25548 
2006       107066      34311 
2007       196351      60510 
2008       117992      33675 
2009        97248      27377 
2010       111831      31167 
2011       165537      45864 
2012       156550      43351 
2013       231089      65775 
2014       574931     146630 
2015       750318     196322 
2016       669532     173366 
2017       570989     154232 
2018       367699     103185 
2019       890146     217458 
2020       642362     163744 
2021       862702     205528 
2022       639788     183128 
2023       579088     165797 
2024       510387     147550