Dichotomies of Mercury and Venus

Mercury and Venus have phases, much like Earth's moon. In a telescope, you may see them as crescents, gibbous disks, or exactly in between as semi-circles. The semi-circle phase is called dichotomy. Listed here are the dates when the geometry says the planets should be at dichotomy. Visual results vary, however, for reasons that are not entirely understood. So, you may see these planets appearing at dichotomy earlier or later than predicted.

When Venus is waxing, it appears to be at dichotomy a few days earlier than the geometry predicts. And when it's waning, dichotomy appears a few days late. A popular explanation is that the planet's atmosphere diffuses sunlight, causing its phase to appear fuller than it should. However, some observers have reported the same phenomenon for Mercury, which has no atmosphere. Perhaps the material that Mercury's made of also scatters sunlight. Or perhaps the illusion happens in our eyes and brains.


Planet Waning (evening object, dichotomy may appear later) Waxing (morning object, dichotomy may appear earlier)
Mercury February 11, 2020 - 00:08
May 29, 2020 - 16:59
October 6, 2020 - 16:48
January 25, 2021 - 07:50
May 12, 2021 - 05:28
September 18, 2021 - 03:06
January 9, 2022 - 13:27
April 25, 2022 - 10:43
August 29, 2022 - 16:41
December 24, 2022 - 15:24
April 9, 2023 - 03:31
August 9, 2023 - 11:30
December 8, 2023 - 11:50
March 23, 2024 - 03:57
July 18, 2024 - 22:56
November 21, 2024 - 00:38
March 7, 2025 - 09:05
June 28, 2025 - 21:35
November 4, 2025 - 03:23
February 19, 2026 - 16:39
June 9, 2026 - 20:28
October 17, 2026 - 17:03
February 4, 2027 - 00:47
May 22, 2027 - 20:43
September 29, 2027 - 14:15
January 19, 2028 - 07:49
May 4, 2028 - 17:03
September 9, 2028 - 15:51
January 2, 2029 - 12:09
April 18, 2029 - 03:45
August 20, 2029 - 20:46
December 17, 2029 - 12:00
April 2, 2030 - 00:12
July 31, 2030 - 10:26
December 1, 2030 - 05:26
March 17, 2031 - 02:57
July 11, 2031 - 00:18
November 14, 2031 - 14:14
February 29, 2032 - 09:25
June 20, 2032 - 08:29
October 27, 2032 - 11:44
February 12, 2033 - 17:27
June 1, 2033 - 18:37
October 9, 2033 - 18:54
January 28, 2034 - 01:19
May 15, 2034 - 04:08
September 21, 2034 - 08:10
January 12, 2035 - 07:22
April 28, 2035 - 07:15
September 2, 2035 - 00:49
December 27, 2035 - 09:58
April 10, 2036 - 22:33
August 11, 2036 - 21:59
December 10, 2036 - 07:20
March 25, 2037 - 22:03
July 22, 2037 - 09:23
November 23, 2037 - 21:26
March 10, 2038 - 02:38
July 2, 2038 - 05:16
November 7, 2038 - 01:50
February 22, 2039 - 09:59
June 13, 2039 - 00:15
October 20, 2039 - 17:40
March 22, 2020 - 11:25
July 26, 2020 - 09:26
November 8, 2020 - 14:40
March 2, 2021 - 14:27
July 9, 2021 - 17:55
October 23, 2021 - 22:45
February 11, 2022 - 16:11
June 22, 2022 - 10:48
October 8, 2022 - 08:58
January 24, 2023 - 15:19
June 4, 2023 - 06:11
September 22, 2023 - 19:31
January 7, 2024 - 08:12
May 14, 2024 - 23:15
September 6, 2024 - 04:39
December 20, 2024 - 14:57
April 24, 2025 - 15:52
August 21, 2025 - 10:25
December 4, 2025 - 08:10
April 3, 2026 - 22:28
August 5, 2026 - 10:25
November 18, 2026 - 09:00
March 14, 2027 - 14:28
July 20, 2027 - 01:41
November 2, 2027 - 15:02
February 23, 2028 - 03:03
July 2, 2028 - 04:11
October 17, 2028 - 00:14
February 3, 2029 - 14:16
June 14, 2029 - 12:37
October 1, 2029 - 10:47
January 16, 2030 - 21:26
May 26, 2030 - 21:11
September 15, 2030 - 20:57
December 30, 2030 - 20:39
May 7, 2031 - 02:57
August 31, 2031 - 04:53
December 14, 2031 - 08:14
April 15, 2032 - 13:04
August 14, 2032 - 08:31
November 27, 2032 - 05:00
March 25, 2033 - 21:28
July 29, 2033 - 05:16
November 11, 2033 - 08:19
March 5, 2034 - 21:23
July 12, 2034 - 15:41
October 26, 2034 - 15:57
February 14, 2035 - 19:48
June 25, 2035 - 11:15
October 11, 2035 - 01:56
January 27, 2036 - 15:55
June 6, 2036 - 10:09
September 24, 2036 - 12:33
January 9, 2037 - 06:23
May 18, 2037 - 07:11
September 8, 2037 - 22:00
December 23, 2037 - 11:18
April 28, 2038 - 02:52
August 24, 2038 - 04:24
December 7, 2038 - 03:12
April 7, 2039 - 09:46
August 8, 2039 - 05:26
November 21, 2039 - 03:05
Venus March 27, 2020 - 01:16
October 28, 2021 - 14:55
June 4, 2023 - 03:20
January 12, 2025 - 02:29
August 12, 2026 - 20:10
March 24, 2028 - 17:49
October 26, 2029 - 02:25
June 1, 2031 - 20:58
January 9, 2033 - 15:10
August 10, 2034 - 10:33
March 22, 2036 - 10:24
October 23, 2037 - 13:42
May 30, 2039 - 14:43
August 12, 2020 - 21:17
March 21, 2022 - 06:11
October 22, 2023 - 22:01
June 1, 2025 - 21:56
January 3, 2027 - 08:44
August 10, 2028 - 13:46
March 18, 2030 - 18:54
October 20, 2031 - 13:06
May 30, 2033 - 13:32
December 31, 2034 - 21:37
August 8, 2036 - 06:39
March 16, 2038 - 07:22
October 18, 2039 - 04:29