Group 1 - The core event of Neptune's opposition occurs on September 23, 2023, providing the best opportunity for observation as it will be at its closest distance to Earth, with maximum brightness and apparent diameter [2][5] - Neptune's brightness during this opposition is approximately 7.7 magnitude, making it invisible to the naked eye and requiring a telescope with an aperture of at least 10 centimeters for observation [5][7] - The opposition of Neptune happens every 367 days, with the previous one occurring on September 21, 2024, and this year's event coinciding with the autumn equinox [2][5] Group 2 - Observers are advised to use Saturn, which has a brightness of about 0.6 magnitude, as a reference point to locate Neptune in the night sky [7] - The close timing of Neptune and Saturn's oppositions, occurring just two days apart, indicates that both planets are moving in a similar manner through the constellation Pisces during late September [5][7]

Core Viewpoint - The article discusses the upcoming western elongation of Mercury on August 19, which presents the best observation conditions for the planet this year, allowing the public to potentially view it in the early morning sky if weather permits [1][2]. Group 1: Observation Conditions - Mercury will be at a horizontal height of approximately 18 degrees at sunrise, with a brightness of 0 magnitude, making it visible to the public [2]. - The observation of Mercury is not limited to August 19; the days surrounding this date also provide good opportunities for viewing due to minimal changes in the planet's height [3]. Group 2: Characteristics of Mercury - Mercury is the most challenging planet to observe in the solar system due to its proximity to the Sun, often being obscured by sunlight [1]. - The planet completes its orbit around the Sun in just 88 days, resulting in 3 to 4 occurrences of both eastern and western elongations each year, with varying observation conditions based on its position relative to the Sun [1].