Telescope and Observing Tips for the 2020 Mars Opposition

If you’ve got a telescope, you’re likely excited for the Mars opposition occurring now—here are some quick tips to make sure you see everything as clearly as possible.

First, make sure you’ve got good “seeing” conditions—that is, that the skies are steady. If the stars are twinkling noticeably, it’s not a good night.

In October, try looking between midnight and 2 AM to get the sharpest, clearest image. Mars is visible low in the east after twilight, but if you aim your telescope at it then, you won’t get as sharp a view as you would if you looked later. That’s because looking near the horizon causes your telescope to peer through many more miles of our atmosphere than if you were looking straight up—in effect, a cause of poor seeing, even in a steady sky.

Give your scope adequate time to cool down to the outside temperature (at least 30 minutes—more with a big scope). You might not imagine that this could make a difference, but it does!

Avoid using magnification greater than your telescope can realistically provide—though it’s easy enough to create huge magnification by putting stronger eyepieces on your scope, the resulting image will get blurry after a certain point, worsening as the power is boosted further. As a guide, keep your magnification to around 25-30x per inch of aperture (so no more than 100-125x on a 4-inch scope, or 200-250x on an 8-inch, and so forth). These numbers assume your telescope is cooled down and you’ve got good seeing conditions (as discussed above); if not, you’ll have to set your power lower to get a reasonably sharp image.

And of course, ensure your telescope is collimated correctly (that is, your optics are well-aligned), and your eyepieces are clean.

Finally—relax! In spite of all the click-bait about “Mars Opposition on October 13th,” you’ll get similar views all the way into November—the exact date of opposition is just the “high water mark,” give or take, for this event, and you have much more time to enjoy the view than you think.

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