A night with Jupiter
- Jeremy Likness
- 17 hours ago
- 8 min read
Last night offered a rare chance to see Jupiter at its brightest and closest point to Earth. This event, known as Jupiter's opposition, made the gas giant an incredible sight in the night sky. Last night, I captured an image of Jupiter that shows one of its moons, Callisto, crossing in front of the planet (known as a transit), while the other three large moons—Io, Europa, and Ganymede—are clearly visible nearby.
If you missed it, don't worry! It will still be bright tonight. Be sure to keep reading for more about the upcoming display on January 23rd when Jupiter is close to the Moon and other planets.
This post will explain what opposition means, describe each of these fascinating moons, and highlight an exciting upcoming conjunction involving the Moon, Neptune, and Saturn on January 23.
Hunting Jupiter
Last night, I did a test run of my equipment to shoot the gas giant from my garage in Newport.
To catch Jupiter, I deployed what I call a "configuration," which is a specific combination of equipment. Different targets require different configurations. Last night, this was the setup:
The telescope I used is the Celestron EdgeHD 9.25" with a native focal length of 2,350mm.
I added a TeleVue PowerMate 2.5x, which effectively increases the focal length to 5,875mm.
The camera I used is the ZWO ASI294MM Pro. This is a monochrome camera. It is not a planetary camera, but I was using my planetary camera in an experiment. I chose this one because it is a high-resolution sensor, so I can crop to the planet and still get decent details.
I used a ZWO Electronic 8-slot filter wheel along with filters for luminance, red, green, and blue from Astronomik.
I set this all up on a ZWO AM5 Harmonic Equatorial Mount. I didn't do any special alignment but positioned it approximately due north before finding the planet.
The planet was located using a method called plate-solving, where the camera takes a picture of the starfield, then determines where it is oriented, and then calculates the offset necessary to move to point at Jupiter.
The mount has a joystick-like hand controller that I can use to manually keep the planet centered as I'm imaging.
The technique I use is called "lucky" imaging and involves taking a short video with as many frames as possible. To do this, I ran SharpCap 4.1, which I highly recommend. SharpCap integrates with all my equipment and allows me to do things like adjust focus and preview images on the fly.
Due to the rotation of the planet, there is a limited window of time to capture an exposure. My experimentation puts that at around 60 seconds per filter. If you expose longer, you risk the rotation introducing blurs unless you use software like WinJUPOS to "de-rotate" it. I also use a feature called "region of interest" that lets me zoom in on the area I want to capture even if it is less than the camera's full field of view. This can increase the speed of acquisition and provide more frames. More frames result in improved signal and detail.
I switched to the luminance filter, recorded 60 seconds, then did the same for the red, green, and blue channels. I then used a program called AstroSurface to stack each of the images. This will center the planet, find the frames with the sharpest details, and blend them for a final image. After it is stacked, there are different algorithms that help reduce noise, increase sharpness, and polish the image. The following diagram shows the progression from a single exposure to the processed image for that "channel".
These are the settings I ended up using:
Luminance - 246 gain, 142ms exposure, 420 frames
Red - 390 gain, 91ms exposure, 657 frames
Green - 390 gain, 91ms exposure, 656 frames
Blue - 390 gain, 91ms exposure, 609 frames
💡Tip: The luminance channel is a filter that just captures the overall intensity of light. It allows the full spectrum in. This is useful to provide detail for the image. Although it's ideal to have the highest fidelity for every channel, if you have a really good luminance image, then you can usually get away with less sharpness in your color channels. The same holds true for deep sky imaging.
I then aligned the images so that they overlap perfectly and blended them into a color image. Here is the final result.
What does Jupiter's opposition mean?
Opposition happens when Jupiter and the Sun are on opposite sides of Earth. This alignment means Jupiter rises as the Sun sets, stays visible all night, and sets as the Sun rises. At opposition, Jupiter is:
Closest to Earth in its orbit
At its brightest and largest apparent size
Best positioned for detailed observation through telescopes or binoculars
Because Jupiter is so close, its features and moons become easier to see. This is why opposition is a prime time for amateur astronomers and sky watchers to observe the planet.
Why last night was a great viewing opportunity
Jupiter’s brightness at opposition can reach magnitude -2.9, making it one of the brightest objects in the night sky after the Moon and Venus. The planet’s disk appears larger, allowing observers to see cloud bands and the Great Red Spot with moderate telescopes.
Last night, the transit of Callisto across Jupiter’s face added an extra layer of interest. A transit occurs when a moon passes directly between Earth and Jupiter, casting a shadow or appearing as a dark spot on the planet’s disk. This event is relatively rare and offers a dynamic view of the Jovian system.
Meet Jupiter’s four largest moons
Jupiter has over 70 moons, but the four largest—Io, Europa, Ganymede, and Callisto—are the most famous. They were discovered by Galileo in 1610 and are called the Galilean moons. Each has unique characteristics:
Callisto
Callisto is the outermost of the four and the second-largest moon of Jupiter. It is heavily cratered and ancient, with a surface that has remained largely unchanged for billions of years. Callisto is transiting across Jupiter in my image, visible as a dark spot moving across the planet’s bright disk.
Io
Io is the closest Galilean moon to Jupiter and the most volcanically active body in the solar system. Its surface is dotted with hundreds of volcanoes, some erupting lava fountains hundreds of kilometers high. Io’s intense volcanic activity is caused by tidal heating from Jupiter’s strong gravity.
Europa
Europa is slightly smaller than Earth’s Moon but has a smooth, icy surface with cracks and ridges. Scientists believe a subsurface ocean lies beneath its ice crust, making Europa one of the most promising places to search for extraterrestrial life.
Ganymede
Ganymede is the largest moon in the solar system, even bigger than the planet Mercury. It has a magnetic field and a mix of rocky and icy terrain. Ganymede’s size and unique features make it a fascinating object for study.
How to spot Jupiter’s moons
Even a small telescope or good binoculars can reveal the Galilean moons as bright points of light near Jupiter. Here are some tips for spotting them:
Look for four bright dots aligned roughly in a straight line around Jupiter.
Use a star chart or astronomy app to identify each moon’s position.
Note that the moons change position nightly as they orbit Jupiter.
What If you missed it?
No worries! It will still be bright and visible the rest of this month. One thing I missed last night was the Great Red Spot. I may try to catch it later in the month. Are you interested, too? Here's what the next few weeks look like for viewing Jupiter from Oregon's west coast (specifically compiled for Newport, Oregon).
Here's a simple chart of what to expect in the coming week:
Date (2026) | Jupiter Rise (≈) | Jupiter Set (≈) | Great Red Spot (good window ±50 min) | Extras you can catch that night |
Sun Jan 11 | 4:43 pm | 7:58 am (12th) | 7:57 pm (7:07–8:47 pm); 5:52 am (12th) (5:02–6:42 am) | — |
Mon Jan 12 | 4:39 pm | 7:54 am (13th) | 1:44 am (12:54–2:34 am) | Io transit ~7:41–9:57 pm (from 03:41–05:57 UT on the 13th). |
Tue Jan 13 | 4:35 pm | 7:50 am (14th) | 9:35 pm (8:45–10:25 pm) | — |
Wed Jan 14 | 4:31 pm | 7:46 am (15th) | 3:22 am (2:32–4:12 am) | Ganymede transit 9:36 pm (13th)–12:53 am (14th). |
Thu Jan 15 | 4:27 pm | 7:42 am (16th) | 11:14 pm (10:24 pm–12:04 am) | — |
Fri Jan 16 | 4:23 pm | 7:38 am (17th) | 7:05 pm (6:15–7:55 pm); 5:00 am (17th) (4:10–6:50 am) | — |
Sat Jan 17 | 4:19 pm | 7:34 am (18th) | 12:52 am (12:02–1:42 am) | — |
Sun Jan 18 | 4:15 pm | 7:30 am (19th) | 8:43 pm (7:53–9:33 pm) | New Moon—darkest skies for fine belt/zone detail & moon shadows.in-the-sky |
Mon Jan 19 | 4:11 pm | 7:26 am (20th) | 2:30 am (1:40–3:20 am) | Io transit 9:25–11:40 pm (from 05:25–07:40 UT on 20th). |
Tue Jan 20 | 4:07 pm | 7:22 am (21st) | 10:21 pm (9:31–11:11 pm) | — |
Wed Jan 21 | 4:03 pm | 7:18 am (22nd) | 6:12 pm (5:22–7:02 pm); 4:07 am (22nd) (3:17–4:57 am) | Ganymede transit 12:52–4:10 am. (Useful shadow relief in the pre‑dawn.) |
Thu Jan 22 | 3:59 pm | 7:14 am (23rd) | 11:59 pm (11:09 pm–12:49 am) | Europa transit 1:13–4:04 am. Great shadow/limb geometry near mid‑transit. |
Fri Jan 23 | 3:55 pm | 7:10 am (24th) | 7:51 pm (7:01–8:41 pm); 5:45 am (24th) (4:55–6:35 am) | Moon–Saturn (with Neptune nearby) close approach in the early evening sky. |
Facts about the Great Red Spot
What's so great about it, anyway?
Location: The Great Red Spot is located in Jupiter's southern hemisphere.
Size: It is approximately 1.3 times the diameter of Earth, making it one of the largest storms in the solar system.
Duration: The storm has been raging for at least 350 years, with some estimates suggesting it could be much older.
Color: The reddish color of the Great Red Spot is still a subject of research, with theories suggesting it may be due to chemicals in Jupiter's atmosphere reacting with ultraviolet light from the Sun.
Wind Speeds: Winds in the Great Red Spot can reach speeds of up to 432 km/h (268 mph).
Shape: The storm has an oval shape, which can change over time, sometimes becoming more circular or elongated.
Changes: Recent observations have shown that the Great Red Spot is gradually shrinking, leading to questions about its future.
Atmospheric Dynamics: The Great Red Spot is a high-pressure system, and its formation is related to the complex atmospheric dynamics of Jupiter.
Observation: The storm has been observed by various spacecraft, including the Voyager missions, Galileo, and more recently, the Juno spacecraft.
Upcoming conjunction on January 23rd
After enjoying Jupiter’s opposition, mark your calendar for January 23rd. On this night, the Moon will appear close to Neptune and Saturn in the sky, creating a beautiful conjunction. A conjunction happens when celestial bodies appear near each other from Earth’s perspective.
This event offers a chance to see:
The thin crescent or gibbous Moon near the faint blue Neptune
Saturn’s iconic rings shining nearby
A stunning grouping visible through telescopes or binoculars
Conjunctions like this provide excellent opportunities for photographers and sky watchers to capture striking images and enjoy the dynamic movements of our solar system.
You don't need a telescope to capture the beauty of the planets! Here is a photo I took of Jupiter with Mars using an ordinary camera and no telescope:
Tips for observing Jupiter and the conjunction
Find a dark location away from city lights for the best view.
Use a telescope or binoculars to enhance details.
Dress warmly and bring a comfortable chair for longer viewing sessions.
Check weather forecasts to ensure clear skies.
Use astronomy apps to track the positions of Jupiter, its moons, and the upcoming conjunction.
Final thoughts
Jupiter is a beautiful, bright target and fun to both observe and photograph. I hope this post has given you some tools and ideas to take advantage of its unique position this month!
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