Mercury greatest morning elongation October 8
Mercury will become visible near the sunrise point around the last few days of September 2022. Mercury will be brightest before sunrise from early to mid-October.
When to watch: Beginning the last few days of September, start watching for Mercury in the eastern sky before sunrise. Greatest elongation – when Mercury will be farthest from the sunrise on our sky’s dome – is on October 8. Then afterwards the planet will continue brightening. So, later in October, although it’ll be edging back toward the sunrise, Mercury will be easier to see in the morning twilight.
Where to look: Look in the sunrise direction, as the sky is lightening.
Greatest elongation is at 21 UTC on October 8, 2022.
Note: As soon as you can spot Mercury – beginning around September 30 – notice that it brightens quickly reaching -0.6 magnitude by October . In fact, it will continue getting brighter reaching -1.1 magnitude near the end of October.
Northern versus Southern Hemisphere
At greatest elongation in October 2022
– Mercury’s distance from the sun on the sky’s dome is 18 degrees.
– Mercury shines at magnitude -0.6 at elongation, and will reach -1.1 magnitude until it slips away in the morning glare at the beginning of November.
– Through a telescope on October 8, Mercury appears 51% illuminated, in a waxing gibbous phase, and 7 arcseconds across. By the way, it will be almost 100% illuminated by the end of October.
For precise sun and Mercury rising times at your location:
Mercury events in 2022 and 2023
Sep 23, 2022: Inferior conjunction (races between Earth and sun)
Oct 8, 2022: Greatest elongation (morning)
Nov 8, 2022: Superior conjunction (passes behind sun from Earth)
Dec 21, 2022: Greatest elongation (evening)
Jan 7, 2023: Inferior conjunction (races between Earth and sun)
Jan 30, 2023: Greatest elongation (morning)
Mar 17, 2023: Superior conjunction (passes behind sun from Earth)
Apr 11, 2023: Greatest elongation (evening)
Heliocentric view of Mercury October 2022
A comparison of elongations
Not all of Mercury’s greatest elongations are created equal. Some are greater than others. The farthest from the sun that Mercury can ever appear on the sky’s dome is about 28 degrees. The least distance is around 18 degrees.
Elongations are also better or worse depending on the time of year they occur. The October 2022 elongation is better from the Northern Hemisphere than the Southern Hemisphere. For instance, the evening apparition of Mercury on August 27, 2022, was challenging for the Northern Hemisphere, but it great for the Southern Hemisphere.
In the autumn for either hemisphere, the ecliptic – or path of the sun, moon and planets – makes a narrow angle to the horizon in the evening. But it makes a steep slant, nearly perpendicular, in the morning. So – in autumn from either hemisphere – morning elongations of Mercury are best. Then Mercury appears higher above the horizon and farther from the glow of the sun. Evening elongations in autumn are harder to see.
Bottom line: Watch for Mercury in the east before sunup in October 2022. Mercury reaches greatest elongation – its greatest distance from the sunrise – on October 8 and remains bright through the end of the month.