Is it possible to view Pluto from a backyard telescope?
Ethan Spyker
Wadsworth, Ohio
If I’m being honest, Pluto is difficult for an amateur astronomer to see. A standard 8-inch telescope just won’t do the trick. That’s because Pluto hasn’t been brighter than 14th magnitude since the fall of 2004. It reached perihelion (its closest approach to the Sun) Sept. 5, 1989, when it peaked at magnitude 13.8. Since then, it’s been moving farther away. That trend won’t stop until it hits aphelion (its farthest distance from the Sun) in February 2114. As I write this, the planet’s magnitude stands at 14.4.
An 11-inch scope will reveal Pluto and a few similarly faint stars, but if you have a friend (or an astronomy club) with a larger instrument, your odds will improve a lot. You’ll also need a site with good seeing (atmospheric stability) and a night with no Moon.
Another thing to take into account is that you want to try to spot Pluto within the time period spanning from a month before until a month after it reaches opposition, the point in the sky opposite the Sun as seen from Earth. That’s when it will stand highest in the sky at midnight. This year, Pluto reached opposition July 23. In 2025, it will be at that point July 25, still at magnitude 14.4. On that date, it will lie in southwestern Capricornus, 9.5′ north of the magnitude 7.8 star SAO 189192 (also known as HIP 100386).
Now, seeing Pluto is one thing, but identifying it is another. Here’s what I mean: Any high-quality go-to mount can point its telescope at Pluto after just a few button pushes. But to truly say that you’ve seen it, you must identify the faint dot in the field of view that’s moving against the background stars. And a single night isn’t long enough for that.
Neither is your memory. So, move your scope to what you think (or what your go-to mount tells you) is Pluto’s position. Insert a medium-power eyepiece. Then carefully — and as accurately as you can — make a sketch of what the eyepiece is showing you. Because Pluto moves on the order of 4″ per day, make your next observation (and sketch) three or four days after the first one. Your brain will quickly identify the pattern of the “stationary” stars. The dot that moved is Pluto.
Although the process required to spot the distant world is time-consuming, you’ll feel a sense of accomplishment having done it. Good luck!
Michael E. Bakich
Associate Editor
