Every two years & two months we are treated to a celestial show as Mars comes calling for a visit. For most of that 26 month interval the size of our brother planet is diminutive - under 5 arcseconds for nearly a year of that time, hovering around Uranus' size (3.8") for nearly 6 months.And as many amateur observers know, not all alignments are equal. Because of Mars' fairly elliptical orbit, the meetup can happen when Mars is at its farthest point from the Sun (aphelion) or when it's near its perihelion (or somewhere in between, obviously!). The difference is significant in terms of how large the disk will appear in the eyepiece (chart below). So perihelic oppositions are almost generational events, taking place every 15-17 years and boasting nearly twice the size of an unfavorable aphelic approach. It's little wonder that the excitement and anticipation for Mars fans has been growing all summer. Heck, I've even seen a lot more interest from the neighbors out for an evening stroll who know that Mars is "up there somewhere". It's a shame that Covid keeps me from sharing more than the image on my computer screen, and my hopes for a fun Halloween activity for the kids is gone as well.
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| Mars Size Over 2 Year Period |
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| Range of Opposition Sizes |
This apparition culminated in a closest approach on the night of October 6th, and opposition almost a week later on October 13th. That may seem odd at first - after all, all the other outer planets have their closest approach synced up with their opposition date. But for Mars we need to factor in its faster orbital rate compared to the gas & ice giants along with its orbit eccentricity. By October Mars was already past its perihelion point of its orbit, so that means with each passing day it draws farther from Earth. So it stands to reason we hit closest approach as a sweet spot a little before opposition since the two planets are pulling away from one another. So here's a pop quiz. The 2018 opposition took place before Mars' perihelion. Would the closest approach happen a few days before or after that opposition?
As if the orbital machinations aren't enough to make a good view of Mars elusive we need to add a wild card into the equation - dust storms. Planet-wide, rover-killing dust storms are not uncommon as the Martian atmosphere warms. And of course, warming is going to be at its most pronounced during the planet's perihelion. The much anticipated perihelic opposition of 2018 fell victim to an impressive global storm that hid features from our prying eyes and instruments for weeks.
But here's the good news - so far this opposition has been relatively free of dust storms, and at over 22" in size the views have been great! I had hoped to have my 10" reflector back in commission in time for the event but that did not pan out. My old reliable 6" RV-6 classic Newtonian has come through, however. On closest approach night using a light red filter (Wr23A) and an 8mm TMB planetary eyepiece (150x) I could see the wedge shaped Syrtis Major/Mare Tyrrhenum feature on the central meridian. A little pearl sat atop the south pole, the receding ice cap as summer has just occurred a few weeks ago for Mars' southern hemisphere. On the setting limb a distinct peninsula albedo feature, Mare Cimmerium, was easy to pick out. One thing I found quite interesting was the rather subdued appearance of Hellas which lies between Syrtis Major and the polar cap. Normally Hellas is quite a bright feature, but this time around it is muted for some reason. You could almost envision the combination of albedo markings looking like a steer head silhouette.
A few nights later near opposition evening I was able to get out and observe a slightly different portion of the Red Planet's globe with the same equipment. Here Syrtis Major was not visible, getting ready to rise on the limb. But Mare Cimmerium was in full view as well as dusky regions south of it where Mare Chronium also appears to be a little darker than I would have expected. And even though it's only been a week, I struggled this night to pick out the polar cap.
I also achieved a life-long desire to image Mars successfully. Two years ago my attempts were undermined by the dust storms and still learning the ropes a bit, acquiring better software and tools over the interval. My most recent addition has been a Baader UV-IR cut filter which serves to enhance images obtained with a color video camera. Playing with PIPP and Autostakkert!3 have also allowed me to tease out as much detail as I can. While I'm no where near the level of the incredible images I see in my role as ALPO AAC (posting images to the gallery), I feel pretty pleased with what I can produce with a smaller instrument and a setup far less costly than the leaders in amateur planetary photography. And after all, it's more about learning and improving, arriving at something that brings you joy and a sense of accomplishment.
So, if you are an amateur astronomer I urge you to give this a go - Mars won't be this good again for 15 years. You don't need a big scope - I have caught albedo features and the polar cap using my 80mm Vixen earlier this summer (Of course by the time you read this the polar cap will likely be dissipated). If you are new to planetary observing then be sure to take your time at the eyepiece. At first you may not make out anything, but keep looking, waiting for those moments of atmospheric stability where you'll grab a quarter of a second of good seeing and pick out a dark marking. As your eye and brain work together you'll end up "integrating" those moments of clarity to fashion an image in your mind of what the planet looks like. Be sure to use a relatively high magnification, perhaps 30-50x your aperture in inches. Hopefully you have tracking ability so that you can relax while viewing the ocher orb, but even if you have to play bump & observe with your Dob, it's still worth it! I'd also suggest a rough sketch of what you are seeing as you observe, it not only gives you a memento for later but will improve your observing skill.
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| Mars with Pastel & Charcoal |
Finally, even with just your naked eye, go out and admire that brilliant orangish beacon rising in the east. Drink in the setting, the place from which you are seeing it, the terrestrial scenery and sounds that accompany Ares as he rises amid the stars of Pisces. Let your mind ponder that at this moment we have rovers on its surface and orbiters whizzing above it, beaming back amazing images of this world. Take comfort in the rhythm and predictability of the heavens, especially now. And perhaps dream that, just maybe, the next time Mars gleams this bright you'll be able to say that humans have set foot on the Red Planet!
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| Doorstep Mars |
Answer to pop quiz: Opposition was July 27 and closest approach happened 4 days later on July 31
