Mars at Opposition

On October 13, 2020, the planet Mars reached a position in its orbit called “opposition” with respect to the Earth. What this means is that the Sun, Earth, and Mars are all lined up so that the Sun illuminates Mars from directly behind us. It actually wasn’t Mars’s closest approach, that happened about a week earlier on October 6. I decided to take advantage of Mars’s opposition to get some photographs.

I used the 8-inch Celestron telescope I received as a high school graduation present in the 1980s. My camera is an Orion Starshoot Eyepiece Camera that takes video. I use free software called Registax 6 to grab frames from the video and combine them into a single, finished image.

The first set of photos I tried were on the night of October 11, just before opposition. It was the most beautiful, clear night I had seen in Las Cruces in a long time. Unfortunately it had been windy during the day, making the atmosphere fairly turbulent. As a result, the images weren’t as clear as I could have hoped. Still, I took two images about an hour apart and was excited to notice that I could see that the planet had rotated from one frame to the next. Note, in the caption below, I use “Universal Time” or “UT” which is based on Greenwich Mean Time. Here in the Southwestern United States, around this time of year, midnight UT happens about an hour before sunset. It can be a convenient way for astronomers to measure time

While preparing for this blog post, I discovered that the website for Sky and Telescope Magazine has a very nice tool that lets you determine the longitude of Mars facing us at a given time of the night. You can find the tool at: https://skyandtelescope.org/observing/interactive-sky-watching-tools/mars-which-side-is-visible/#

With the longitudes in hand, I went back to my handy copy of A Photographic History of Mars: 1905-1961 by E.C. Slipher of Lowell Observatory and found photos of Mars that are similar to the longitudes I show in my photos above. It was gratifying to see my images with an 8-inch telescope compare somewhat favorably with images attained by the Lowell Observatory 24-inch telescope in 1941.

I went back out on the night of October 17, which proved to be a much more stable night. Unfortunately, there were some high clouds, but in my experience, those sometimes stabilize the atmosphere. I took a longer sequence of images and obtained a truly beautiful image of Mars. Just for comparison sake, Sky and Telescope’s calculator says it would be centered on longitude 200 degrees, which is close to the left image above.

Mars at 3:43UT on October 18.

I was very pleased with this last image about five days after opposition. It compares very well with images that were taken at Lowell Observatory on photographic plates. I also noticed that I captured a very small hint of the north polar cap in my photograph.

For fun, I also took images of Saturn and Jupiter both nights. The ones from October 11 aren’t very good, but here are my images from October 17.

Saturn

When I took my image of Jupiter, I wanted a “family portrait” showing the planet with the four Galilean moons that are easily visible in my 8-inch telescope. As it turns out, the human eye has better dynamic range than my Orion Starshoot camera. To photograph the moons, I had to overexpose the planet. So the image below is a little bit of photographic trickery. I took an image to capture the moons, then I took a second image to capture details on the planet. As the two images were taken back to back at the same orientation, I just overlaid one image over the other to get my family portrait. The moons, from left to right are Ganymede, Io, Callisto, and Europa.

A Jovian family portrait.

As I write this, preparations are underway to reopen Kitt Peak National Observatory after it was shut down due to the COVID-19 pandemic. Once I get back to work, I’ll be working with much larger telescopes and much more sophisticated instrumentation than my 36-year old Celestron and its little video camera. Even so, there’s nothing like sitting out on a dark night, looking across the gulf of space and dreaming of what it would be like to visit the planets in person.