Six observations per day, standard approach day observation sequence source days observed note twice once 1 A B C A D E a A 1 3 fiducial 2 A B F G D C - B 0 4 fiducial 3 A B E F G C - C 0 3 primary 4 A B E F G D - D 0 3 secondary . A B C D E E 0 3 secondary F 0 3 tertiary G 0 3 tertiary day observation sequence source days observed note twice once 1 A B C D E F - A 0 5 fiducial 2 A B G H I C - B 0 4 fiducial 3 A D E F G H - C 0 3 primary 4 A B C I D E - D 0 3 secondary 5 A B F G H I - E 0 3 secondary . A B C D E F 0 3 tertiary G 0 3 tertiary H 0 3 tertiary I 0 3 tertiary day observation sequence source days observed note twice once 1 A B C D E F - A 0 6 fiducial 2 A B G H I J - B 0 6 fiducial 3 A B C D E F - C 0 3 primary 4 A B G H I J - D 0 3 secondary 5 A B C D E F - E 0 3 secondary 6 A B G H I J - F 0 3 tertiary . A B C D E G 0 3 tertiary H 0 3 tertiary I 0 3 tertiary J 0 3 tertiary day observation sequence source days observed note twice once 1 A B C A D E a A 1 6 fiducial 2 A B F G H I - B 0 7 fiducial 3 A B J K D E - C 0 3 primary 4 A B C G H I - D 0 3 secondary 5 A B F K D E - E 0 3 secondary 6 A B J G H I - F 0 3 tertiary 7 A B C F K J - G 0 3 tertiary . A B C D E H 0 3 tertiary I 0 3 tertiary J 0 3 tertiary K 0 3 tertiary day observation sequence source days observed note twice once 1 A B C D E F - A 0 8 fiducial 2 A B G H I J - B 0 7 fiducial 3 A B K L M F - C 0 3 primary 4 A B C D E I - D 0 3 secondary 5 A J G H K L - E 0 3 secondary 6 A B C D E M - F 0 3 tertiary 7 A B G H I F - G 0 3 tertiary 8 A B K L M J - H 0 3 tertiary . A B C D E I 0 3 tertiary J 0 3 tertiary K 0 3 tertiary L 0 3 tertiary M 0 3 tertiary day observation sequence source days observed note twice once 1 A B C D E F - A 0 9 fiducial 2 A B G H I J - B 0 9 fiducial 3 A B K L M N - C 0 3 primary 4 A B C D E F - D 0 3 secondary 5 A B G H I J - E 0 3 secondary 6 A B K L M N - F 0 3 tertiary 7 A B C D E F - G 0 3 tertiary 8 A B G H I J - H 0 3 tertiary 9 A B K L M N - I 0 3 tertiary . A B C D E J 0 3 tertiary K 0 3 tertiary L 0 3 tertiary M 0 3 tertiary N 0 3 tertiary