Mercury, Jupiter, and Saturn in the Evening Sky

A few weeks ago Jupiter and Saturn passed very close to each other during the Great Conjunction of 2020. Jupiter and Saturn are now pulling away from each other and are lower in the southwestern sky—but they have been joined by Mercury resulting in a planetary triplet viewable in the twilight.

Mercury, Jupiter, and Saturn in the evening sky.
Mercury, Jupiter, and Saturn in the evening sky.

This is a composite of three images taken over successive nights (09–11 January 2021) that shows the relative motions of the planets Mercury, Jupiter, and Saturn in the southwestern sky. The images have been aligned using Saturn as an anchor point.

Mercury, Jupiter, and Saturn on 09 January 2021.
Mercury, Jupiter, and Saturn on 09 January 2021.

From this composite, one sees small daily motions of Jupiter as it continues to move eastward away from Saturn—which had their Great Conjunction on 21 December 2020. Mercury exhibits large daily eastward motions as it races toward its greatest eastward elongation on 24 January 2021.

The Great Conjunction of Jupiter and Saturn

Great Conjunction of Jupiter and Saturn (21 December 2020)
Great Conjunction of Jupiter and Saturn (21 December 2020)

On 21 December 2020, Jupiter and Saturn passed a tenth of a degree from each other in what is known as a Great Conjunction. Great Conjunctions are not rare and occur every 20 years. But the apparent separation between the two planets varies with each event and this one was the third closest in over 800 years (1226 and 1623 were closer) but only one of these was visible; the other was lost in the bright glare of twilight.

Great Conjunction with labels of Jupiter and Saturn (21 December 2020)
Great Conjunction with labels of Jupiter and Saturn (21 December 2020)

The images shown here used a 300mm telephoto lens—which is barely sufficient to resolve the rings of Saturn. The rings can be seen as making Saturn appear oval shaped.

The first image is from 1803 MST on 21 December 2020, just a few hours after closest approach. The second image has labels for the brightest moons of Jupiter and Saturn.

Below is an image showing the daily movement of Jupiter relative to Saturn. It is also easy to see the motions of Jupiter’s four largest moons as they appear in different locations for each of the three Jupiter positions.

Three-day sequence of the Great Conjunction of Jupiter and Saturn.
Three-day sequence of the Great Conjunction of Jupiter and Saturn.

Finally, NASA’s Astronomy Picture of the Day has a very nice image of the two planets. Telescope required.

Crescent Moon Joins Jupiter and Saturn in the Evening Sky

The planets Jupiter and Saturn are drawing closer to each other in the evening sky with each passing day and will be at their closest on December 21st. In the meantime, the crescent Moon moved through the same part of the sky making a nice triplet in the evening twilight.

Here are views from two nights of the Moon, Jupiter, and Saturn.

Moon, Jupiter, and Saturn in evening twilight.
Moon, Jupiter, and Saturn in evening twilight.
Moon, Jupiter, and Saturn in evening twilight.
Moon, Jupiter, and Saturn in evening twilight.

Four Planets in the Morning Sky

For several weeks the planets Mars, Jupiter, and Saturn have been visible in the same portion of the morning sky. These are all bright and easily visible even during twilight hours. Nestled in between these bright planets lies the minor planet Pluto.

Mars, Jupiter, Saturn, and Pluto.
Mars, Jupiter, Saturn, and Pluto.
Stellarium star chart showing positions of the planets in the morning sky.
Stellarium star chart showing positions of the planets in the morning sky.

So I thought it would be interesting to photograph Pluto. Pluto is much too faint (currently Mag. 14.3) for me to find with my camera/lens setup. However, Pluto and Mars passed very close to each other (~10 arc minutes, or less than the diameter of the Moon) on 23 March 2020 making it easier to find one based on the location of the other. Clouds forced me to shoot this image a day later on 24 March 2020, when they were farther apart.

Pluto and Mars.
Pluto and Mars.
Pluto.
Pluto.
Stellarium chart showing Pluto and neighboring stars.
Stellarium chart showing Pluto and neighboring stars.

I used Stellarium as a guide to hopping from one star to another—comparing the photographs with Stellarium star charts—until I finally located Pluto. As a magnitude 14.3 object, this was near the limit of what could be resolved with my Nikon 180mm AI-s ƒ/2.8 lens shot wide open.

Images were shot at ƒ/2.8, ISO 1600, and 30s. The best images were stacked to reduce noise. Post processing included large values of Unsharpen Mask to help sharpen the dimmest stars and Pluto—with the undesired side effect of creating halos around the brighter stars.

Check the video to see how much Mars moves in just 15 minutes.

I was able to capture four planets in the morning sky. In the previous post, I was able to capture four planets in the evening sky. It was a challengin project that I wanted to do and have now completed.

Maybe I should get a telescope.

Starlink cluster.
Starlink cluster.

Oh, one final point. Once again I was photo-bombed by a cluster of Starlink satellites. Sadly, the day is coming soon when night photography will be very difficult because of these satellites.

Four Planets and the Moon

This week the waning moon joined four planets in the eastern sky. Lowest to the horizon was Mercury with Saturn just above. The moon was located well above that pair. And high in the sky were Mars and Jupiter.

Earlier this month on 07 January 2018, Mars and Jupiter were in conjunction. The pair was only 0.25 degrees apart in the sky at its closest. By comparison, the full moon is approximately 0.50 degrees. And, then, on 13 January 2018, Mercury and Saturn were in conjunction—but not quite as close as the Mars-Jupiter conjunction.

On the 14th and 15th, the Moon was just above and just below the pair of Mercury and Saturn.

The waning crescent moon (~5% illuminated) sits above the planetary pair of Mercury and Saturn.
The waning crescent moon (~5% illuminated) sits above the planetary pair of Mercury and Saturn.
A wider view shows all four planets (Mercury and Saturn low; Mars and Jupiter high) plus the moon.
A wider view shows all four planets (Mercury and Saturn low; Mars and Jupiter high) plus the moon.

I had planned to photograph on both days but clouds intervened. All I got was this thin crescent Moon (~2% illuminated) that was visible for only a few minutes before it was obscured by clouds.

A thin crescent moon is visible for just a moment after moonrise.
A thin crescent moon is visible for just a moment after moonrise.

Coming up: at the end of the month there will be a total lunar eclipse that will be visible in the pre-dawn hours of the western states. I hope the skies are clear.