An “opposition” happens on the day that Earth and an outer planet line up on the same side of the Sun. For Earth observers, a planet in opposition will rise when the Sun sets and will be in the sky all night. Around the time of opposition, the planet is brightest, practically fully illuminated, and displays the largest angular diameter for the year. Right before, during, and after opposition are prime-time for viewing and imaging a planet!
Amateur and large observatory scopes can do best when imaging planets at opposition. It was just announced this summer that amateur astronomer Kai Ly discovered an unknown moon of Jupiter while examining opposition images taken with the 3.6-meter Canada-France-Hawaii Telescope at Mauna Kea Observatory in Hawaii. This news comes just in time to take some confirmation images as Jupiter opposition season is upon us now!
Even though we’re past the point of closest approach and opposition, Mars continues to loom large in the sky and is higher each night at the same time. In the northern hemisphere, the nights are coming sooner and lasting longer. Until mid-November, Mars will appear bigger than at any opposition until 2033!
You can use the excellent Mars Mapper 2020-2021 web app (mobile version) on the British Astronomical Association website to identify features on the planet when you observe or image it.
If you’d like to try your hand at imaging the planet, study the next sections carefully as they contain image processing tips from top Martian imagers on the Internet.
We’ve reached the peak of the current Mars observing season with the planet closest to Earth:62-million km or 38.5-million miles on October 6/7th. At -2.5 magnitude and 22.6″ in diameter, Mars is a conspicuous, intense orange target in the sky that is brighter than any star, except our Sun and is only outshone by Venus and the Moon in the nighttime sky. When it reaches opposition next week, on October 13th, it will still be 22.4″ in diameter and a tad brighter at -2.6 magnitude. It will remain greater than 20″ in diameter for the whole month. So, weather permitting, put an eyepiece in the scope this month and show it to all your friends!
The public will likely learn from the media that the Mars Opposition is a “one-night” event, on October 13th, when the planet rises at sunset and is brighter and larger in appearance than usual. However, amateur astronomers know that the 2020 Mars Opposition is more like a “season,” where the planet grows in size each night over months, stays near peak size for a while, and then slowly fades away over the weeks. This gives us an observation window much longer than a single night!
Mars is growing daily in size and brightness as it approaches opposition night on 13 October 2020. On that date, the “Red Planet” will shine at magnitude -2.6 and be 22.4″ in diameter. At 5.5° above the Celestial Equator, it will be well placed for northern observers. Enjoy it while you can as it will not reach 22″ again until the year 2033! See our prior post on the Mars Opposition to learn why this will be the Last “Best” Mars Opposition for Northern Hemisphere!
The Mars 2020 opposition will be the “best” this decade for mid- and high-northern hemisphere observers.
Let’s start out by stating that the Mars 2020 opposition will be the “best” one this decade for mid- and high-northern hemisphere observers. (Better even than all the ones in the 2010s!) On opposition night, 13 October 2020, the “Red Planet” will be brilliant in the sky at magnitude -2.6 and 22.4″ in diameter at a Declination of 5.5° above the Celestial Equator. It will reach 44° in elevation above the horizon in the city of London, UK.
(Due to the non-circular orbits of Earth and Mars, the instant of opposition is not usually the same as the closest approach between the pair: there can be a two-weeks difference in time. So, we’ll talk in round numbers when discussing the size of Mars around the time of opposition.)
With regard to this year’s event: yes, there have been “bigger” oppositions. In 2018 Mars was 24” in diameter (ranking with the super-duper, 2003 opposition that had Mars at 25″). However, while Mars was bigger in 2018, it was at -25.4° Declination and barely cleared your neighbor’s fence in the northern hemisphere. This year it’ll be +30.9 degrees higher in the sky!
Andrew Thomas has been posting beautiful wide-field sky images on his Flickr feed. He’s imaging with one of our smaller scopes, the highly portable and capable Tele Vue-76 APO refractor! Here’s an image made by Andrew with this scope during the Great American Eclipse in August 2017.
Andrew gave us permission to re-post these photos on our blog.
I’m glad you enjoy the images I’ve been able to capture with the Tele Vue-76. It’s a wonderful scope for both visual use and imaging. I don’t think I’ll ever give it up!
Anis Abdul’s composite image of Uranus and moons is from the October 2017 opposition and was posted to his Facebook page. The imaging gear used was a Celestron Edge 11 telescope, riding on on AP900 mount, that was “amplified” with our Tele Vue 2.5x Powermate to achieve 7,000 mm focal length. Imaging was done with a ZWO ASI224MC color camera . The best 50% of frames from 20-minutes of video were processed for the image. Software used was Pixinsight and Registax.
“One of the closer moon (Miranda) is actually visible in my stacks but is lost in the planet glow ,” says Anis.
The “ice giant” planet Uranus was in opposition on October 28th. That means that the Sun, Earth, and Uranus all lined up together at an instant in time on that date. Uranus is on the same side of the Sun as the Earth, so the planet was closest to Earth and brightest for the year and in the sky all night long. If you missed it: don’t worry. The slow-moving planet will remain at least 3.7″ of arc in diameter and at magnitude 5.7 for the next month.
On June 10th, Jupiter was closest to the Earth and rose at sunset — placing it in the sky all night long. The timing makes it well placed for observation throughout much of the summer. Currently, the planet is at its best for the year, at magnitude -2.6 with an angular diameter of 46-arc-seconds. It will “fade” slightly to a still very bright magnitude -2.1 and shrink to 36-arcseconds by the start of fall, where it will be in the west at sunset, setting just a few hours later. So, now is prime-time to view and image this gas giant planet, its famous Great Red Spot (GRS), and attendant giant moons.
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