Derekscope

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Mercury at greatest elongation west

• Mercury will reach its greatest eastern elongation, meaning it will be farthest from the Sun in the evening sky.
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• Look in the western sky, shortly after sunset.
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• Mercury’s low position in the autumn evening sky will make it difficult to see, particularly from the UK.
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• Clocks go backward an hour at 2am on the last Sunday this month.
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• At 2am British Summer Time, the clock goes backward to 01:00UT (Universal Times).
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• The timing is favorable because of close approach the comet may reach a brightness that allows visibility with binoculars (e.g. ~ 7×50, 10×50, 15×70 or more to increase your chances) – maybe even the naked eye under dark skies.
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• Look after sunset, toward the northwest horizon, the comet moves into the constellation Bootes and near the bright star Arcturus.
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• The comet is described as having a greenish coma and potentially showing a tail making it visually interesting ~ however it can be unpredictable, actual brightness and tail length can vary and local conditions (horizon, light pollution, weather matter, etc).
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Look out for Comet Lemmon (C/2025 A6)

• It is easy to find this evening located the star Izar, after the sunset.
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• Find Izar is a star in the constellation Boötes is home to the bright orange star Arcturus.
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• Comet Lemmon will be positioned about 2 degrees to the left of Izar.
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• It may be bright enough to see without optical aid under dark, light-pollution-free conditions, but binoculars are recommended for the best view.
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• Even if visible to the naked eye, expect to see a fuzzy, white or bluish glow rather than a distinct point of light in the dark location.
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Look out for earthshine

• This celestial alignment, a conjunction of the Moon and Venus, is a treat visible to the naked eye and can be framed with a scenic backdrop for photos.
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• Binoculars can enhance the view of the faint glow on the Moon’s dark side, known as earthshine.
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Moon & Venus

• See the bright planet Venus alongside a very thin, crescent-shaped Moon, with both objects relatively close together.
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• The Moon will be a waning crescent, meaning it will be a thin, sliver-like shape, just days away from its New Moon phase.
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Comet Lemmon (C/2025 A6) is your pick this month

• It is brightening fast and now (mid-October) is becoming a binocular ~ possibly naked-eye object in the dark skies.
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• Its closest approach to Earth occurs on Tuesday 21st October 2025.
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• It will move from being a pre-dawn object to being visible after sunset in the western sky in late October.
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• Use a star chart or astronomy app in explaining BSL that can show you where Lemmon C/2025 A6 is.
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Algol
(bright variable Star Beta Persei)

• The bright variable Star Beta Persei (Algol) reaches minimum brightness.
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• This variable star in Perseus varies from its brightest at magnitude +2.1, dropping to +3.4.
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• Even when dimmed, Algol is still visible to the naked eye.
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• Read more – Algol
  – How to find Algol in Perseus?
  – Deaf astronomer John Goodricke
  

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Moon near the Beehive Cluster

• Messier 44 (The Beehive Cluster) is one of the most famous deep-sky objects.
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• The moon and cluster will be visible low in the east-northeastern sky just before sunrise, though binoculars will greatly help to spot the faint Beehive.
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