Astroblog: Seeing the Lunar X, Friday, August 1, 2025

Thursday, July 31, 2025

Seeing the Lunar X, Friday, August 1, 2025


Western evening sky on Friday, August 1 as seen from Adelaide at 20:17 ACST	Western evening sky on Friday, August 1 as seen from Melbourne at 20:57 AEST	Western evening sky on Friday, August 1 as seen from Perth at 18:57 AWST

The Lunar X (also known as the Werner X) and the Lunar V will be visible this Friday as the Moon reaches First Quarter. The Lunar X is a chiaroscuro effect in which strong contrasts of light and shadow create the appearance of a letter 'X' on the rim of the Lunar craters Blanchinus, La Caille and Purbach and a letter V from the rim of the crater Ukert, along with several smaller craters.

The X and V are seen at first quarter, visible on the lunar surface for about 4 hours. However, the Moon is not always above the horizon from a given vantage point when this happens. This month is good for Australian observers, with the Moon moderately high above the horizon in the eastern sates, and quite high on the west coast.

Lunar X occurs on Friday, August 1, 10:57 UT, 20:57 AEST, 20:17 ACST, 18:57 AWST). This is earlier than official first Quarter which occurs at 22:11 ACST.

This is a telescope (and maybe good binoculars) only event. For the west coast the start of the Lunar X occurs with the Moon being 70° above the horizon, central states see it at 53° above the horizon, and for the east coast at 45° above the horizon.

Upcoming Lunar X' s are shown below:

Dates and time Lunar X and V are visible. Typically visible from about 4hours from the starting time, times in colour are daylight saving times.

Date	UT	AEST	ACST	AWST
Feb 5	08:13	21:13	20:43	16:13
Apr 5	12:43	23:43	23:17	20:43
June 3	13:18	23:18	22:30	21:18
Aug 1	10:57	20:57	20:17	18:57
Sep 29	08:46	18:46	18:16	16:46
Nov 27	10:43	21:43	21:15	18:43