Thursday, November 19, 2020

how many planets can you see?

What can you see? Which planets? 

Need to do some myth-busting, again. The news media outlets are not presenting information correctly or clearly—but of course you must question their motives. Gotta sell newspapers, right? 

It was disappointing to hear a prominent astronomical Canadian society get it a little bit wrong.

body eyes binoculars
Mercury yes yes
Venus yes yes
Mars yes yes
Jupiter yes yes
Saturn yes yes
Uranus maybe yes
Neptune no yes

Uranus is a borderline object, hovering around magnitude 5.6 and 6.0. I have seen it with my Mark I eyeballs. A dark sky location without moonlight is required. Age is a factor—the younger astronomer's pupils can dilate larger. But experience is a factor too. It is said an expert observer can see a magnitude deeper than a novice.

Again, you cannot see Neptune with your eyes! Not without aid. Common 7x50mm binoculars have a limiting magnitude of 11.0. As Neptune hovers around mag 8, it's well within the range of binos. Or a small telescope.

All that said, remember that Uranus and Neptune will be tiny unless you employ significant aperture and magnification. But probably a 6-inch or larger telescope with over 100x power will show a disc. 

Orbital position is a factor, of course, with Mercury varying the greatest, from magnitude -3 to 6. Mars also varies a good amount too, -2-ish to 2. Needless to say, you cannot see planets when they are terribly close to the Sun, from our perspective.

Don't forget the trick to the question too. Look down, past your feet. There's another planet.

Now if you do have good binoculars or even a small telescope, when you consider other possible solar system objects, the number jumps rapidly. There are many asteroids and dwarf planets, such as Ceres, Flora, Vesta, Pallas, Iris, Psyche, Juno, Metis, and so on, that can be within the magnitude 11 range.

Pluto? Ex-planet? It's around mag 14. You need a big gun to see it...


So, to be clear...

Can you see all the planets tonight? Yes, using binoculars or a telescope.

Can you see all the planets naked eye? Never.


Made a graph to compare all the mags for the next year.

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