Observing Pluto

Observing Pluto

Jul 28
Last night I fulfilled a longstanding ambition: I saw Pluto. The dwarf planet is extremely hard to see. You need exceptionally dark skies, a decent telescope and a hell of a lot of patience! I had previously doubted that the Meade ETX90 could even see it, and rightly so. There is an equation to help you work out how far down the magnitude scale you can get with a telescope (Remember big magnitudes = fainter objects):

Telescope Limiting Magnitude = Visual Limiting Magnitude - 5*logd + 5*logD

, where d is the aperture of the human eye and D is the aperture of the telescope. So to give some examples, let's consider a normal sky where the visual limit is around Mag 5.5 and you have a little 3-inch refractor telescope. We'll use 3mm as the aperture of the human eye.

Telescope Limiting Magnitude = 5.5 - 5*log(0.003) + 5*log(0.07) = 12.3

So with a small refractor you can see down to a limit of about Mag 12. Pluto however is at Mag 13.8 so this would not suffice. Here is the maths for my own situation. Last night the sky was so dark I could make out Mag 7.0 stars, this is my visual limit and it is about right for very good observing conditions. The telescope I am using has a 9cm aperture.

Telescope Limiting Magnitude = 7.0 - 5*log(0.003) + 5*log(0.09) = 14.8

This puts Pluto into the realms of the feasible, which was great news since Pluto from my location is well above the horizon and unobscured by light pollution. Also, this week I have set myself the goal of observing all the planets, and Pluto - just for fun. Pluto can currently be found in Sagittarius at the painfully dim magnitude of 13.8. Along with its sister body Charon and two satellites Nix and Hydra, it is a very cold, dark and far away place. Even the best images ever taken of Pluto reveal little more than a patchy ball of rock. I was unable to take a picture myself, far too dim, but Googling reveals a handful of amateurs have succeeded.

The image above is taken from Mauna Kea and the one below comes from an amateur named Bill Dirk.

If you want to try and see Pluto, I can now recommend a few things to help you along. Firstly, check that you have dark enough skies. This isn't trivial, I have rarely had as good conditions as last night. Unless you have a very big telescope (more than 15cm) you'll find Pluto is beyond your reach in anything other than exceptional skies. Secondly, know where to look. Using the Meade with a good calibration means that getting into the general vicinity of Pluto is fairly easy. you need to know your stuff if you're using a regular, manually guided telescope. Whatever happens, you need tracking, other wise the objects you find will vanish before you can see them at all. Thirdly, get a good map of the planet's location and memorize the patterns of stars around it. Once you're looking at a star-field in the eyepiece, it will look the same as every other star field, unless you know what you're after. Most planetarium software will give you this, the trick is figuring out the field of view you will be looking at through the eyepiece. I recommend using the 12DString FOV Calculator. Finally, have patience. This will take time and several attempts. Even if you do find it, if you're like me you'll feel the need to verify everything twice anyway. But I think it was worth it!

Having finally seen Pluto I am now compelled to complete my planetary observation collection. All of the planets are visible during the night at some point from my current spot. I will not be here much longer so I need to get out and see them all. I have never yet seen Neptune or Uranus and I have only seen Mercury twice. I'll report back later in the week.

34 comments

  1. Agrade

    I love how you mention Charon – it’s a pity mainstream publications leave it out !

  2. Lil

    the picture is cute of pluto and all the other planets

  3. lisa

    ha that pics funny!

  4. I never did find this little guy we call pluto. I might have seen it without even knowing it at one point. One thing about astronomy some of these things are very challenging.

  5. meghan

    IT IS A PLANET !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

  6. meghan

    JUST BECUAE ITS SMALL DOST MEANS ITS NOT A PLANET!!

  7. TS A PLANET!!!!!!!!!!!!!! LET IT BE A PLANET AGAIN PLUTO IS SMALL BUT IS STILL A PLANETITS SMALL AND IT HAS FEELINGS TO

  8. pluto has fellings to

  9. dhänìztìç

    what a nightmare. pluto is not a planet. poor pluto.

  10. Canadian

    Poor Pluto… XD!!

    Very good picture

  11. Scott

    Poor Pluto… But for your information Pluto is not a planet because it doesn’t follow a normal orbit around the sun and it is so far off. Pluto is probably a moon or another celestial object, but not a planet…

  12. poor pluto!!!!!!!!!!!

  13. Juan Reyes

    pluto is such a cutie, i would look at it trough photos and always imagined myslef cuddling and loving sweet sweet pluto.

    planethood! delta epsilon, ra ra ra!!!!!!!!!

  14. Sboing

    Pluto isn’t a planet it’s to small, and no Gravitational Pull our charts, plus, it’s ugly..

  15. sally

    poor pluto! the planets kicked pluto out and made him back his stuff. now pluoto’s no planet just because of ” the bigger ones”

  16. wow

    wow iam in a bad mood and this mad me laugh

  17. oh my god!!!!!!!!!!! I feel totally feel soooooooo sorry for Pluto! i wish the other planets accepted it as a planet so that we all could live happily and peacefully on the large earth again. and Mars is sooo totally mean. i thought humans could live on Mars in the future but know i have totally changed my mind. i will never even dear to put a footstep on the mingin mars!!!!!
    hi people :)!

  18. Jane

    Hey, plutos cool

  19. uhhh...

    wow…everybody’s acting as if pluto is some person whose mom just died…that’s really wierd and I agree with that scott person, pluto isn’t a planet, so boohoo to everybody else.

  20. Pluto is a planet. Only four percent of the IAU voted on the controversial demotion, and most are not planetary scientists. Their decision was immediately opposed by hundreds of professional astronomers in a formal petition led by Dr. Alan Stern, Principal Investigator of NASA’s New Horizons mission to Pluto. This debate is far from over.

    Viewing Pluto is one of my lifelong ambitions. Last week, I saw Neptune for the first time, and even though it was just a tiny blue dot, I was absolutely thrilled!

  21. Jazz

    Arrr…Pluto…
    I love what all you guys have said. How funny. I fell sooo sorry for Pluto.
    All give an arrrrrr for Pluto.

  22. DTzQuincy

    1st off Pluto does have a gravitational pull.. that’s why it was discovered and given the title of planet in the 1st place. It pulled on both Uranus and Neptune. It’s moon is nearly the size of it and yes it isn’t exactly on the same plane as the other planets and has an awkward orbit. Ofcourse, it also has a different element content from the outer planets as well, but maybe there is something more to it. Maybe it’s made up of several planetesimals and comets. Perhaps even a planetesimal knocked it off course just like they supposedly wreaked havoc on mercury, venus, earth, and uranus (no pun). [Explained: Mercury doesn't have much of an atmosphere and is mostly core, earth is tilted and possibly the moon is made up of earth chunks and the planetesimal, venus could've gotten hit and ended up spinning backwards, uranus spins backwards and on its side it's all messed up!]

  23. ms.perfect

    pluto is so pretty!!!!!!! and also pluto is not a planet its another moon i really dont know why every one is making it such a big deal.for the people that think pluto is a planet get this in your head, PLUTO IS NOT A FUCKING PLANET STUPID MOTHER FUCKERS

  24. I will say that pluto is about the same size as Mars. In the future i think that mars will become a possibile dwarf Planet

  25. Pluto is a planet according to the Texas law!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

  26. Will

    I’m doing a school project on planets, dwarf planets, or moons. I chose to do it on Pluto cause I think it’s a poor little guy being forced to be called a dwarf planet instead of a real planet. I wish they still considered him a planet. That picture of all the BAD planets looking at him in a mad sort of way really isn’t nice. The picture depicts what is true POOR PLUTO!!!

  27. my face

    whoever said that pluto is ugly will suffer the wrath of pluto! pluto is growing. somewhat. and:PLUTO IS A PLANET!!!!!!!! so all you other people out there who are stupid enough not to study this further, shut up! and pluto is a guy whos mom died. cause you guys who arent even real scienetists say he isnt a planet. so THERE!!!!!

    pluto is also mickey mouses dog

  28. Tracy

    Where is the Sun in the picture?

  29. Stoode

    Check your equation – me thinks you have a +/- mixed up!

  30. some guy

    wow did he say he doesn’t have much longer to see the planets? is he dying? wow that’s sad… you go “guy who’s life isn’t much longer” you see those planets, don’t give up!

  31. Athena

    You know. Everyone says Pluto isn’t a planet. Everyone says,” Shut Up! Pluto IS a planet.”
    Also, my face, your very wrong. I know many astronomers. I want to be one. I go to a astronomy school. Anyways, the picture is fake. So…what’s the problem about Pluto? Why fight when we can discover? We are waisting our time! We should start thinking, with our brains, not with our hearts. There is a friend of mine who said,” I feel so bad for Pluto. It should be a planet. Not a dwarf planet.”
    But haven’t you noticed? A dwarf planet is a special one. So think on the bright side,” Pluto is special.”
    look in other people’s point of view. Think of what the person who made the thing called Pluto is a “dwarf planet”. Well? This Solar System isn’t controled by us. We only give opinions, we can’t tell. Because, the Solar System is always what it is. So, to the earth, earth is a place, not a human, not a planet with feelings. They are just…there. So, you can’t ever say that there pluto isn’t a planet, and you can’t say pluto is a planet. haven’t you noticed this picture made you happy or mad? This conversation comes fomr PLUTO!
    What is right, is…
    The people on earth are the ones that said this. but are they right? Maybe from there brains. But they aren’t the Solar System. They can’t just say that. They ahve no right to say that. Maybe we should leave this alone. Maybe it isn’t a good idea to remember Pluto, maybe it is. Maybe it’s time to stop guessing and argueing, maybe we should let this Solar System it’s self tell us the fate of Pluto!
    I hope I did not offend anyone.
    I’m just saying what I think seems right.

  32. You may call Pluto a planet.
    But then those also are planets: Eris, Makemake, Haumea, Sedna, Orcus, Quaoar and 2007 OR10.
    http://en.wikipedia.org/wiki/Plutoid
    http://en.wikipedia.org/wiki/File:EightTNOs.png

  33. Rekaya

    I actully have real tears because the planets are being mean and pluto is so sad.
    poor little pluto.

  34. I actully had real tears when I saw this picture poor pluto!
    it is a planet even though it is small.

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