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Welcome to the annual Pluto Challenge: since the year 2000 this page has been helping amateur astronomers "discover" Pluto -- the most neglected and controversial of (dwarf?) planets. Two "challenges" are presented here. They are meant to encourage small-scope users to push the boundaries of technology and achieve the goal of viewing and/or imaging Pluto. All the advise, charts, and links, to help you accomplish this task are here. During "Pluto season" -- from yearly opposition to disappearance in the solar glare -- this page is updated -- so check back often. The Pluto Challenge topic of the Message Board is a good place to post public information and read a compilation of comments from other Pluto observers. You can also e-mail suggestions, observations, and images.  

Pluto and You

Have you seen Pluto lately? With the (dwarf?) planet at opposition in June, late spring is a good time to start looking. Most beginning amateur observers have trained their telescopes at the brighter, naked-eye planets numerous times. Next-up, in planet spotting difficulty, is discerning the disks of Uranus and Neptune, through a telescopic star-hop. But, how many amateurs out there have "done" all the (dwarf?) planets, by viewing disk-less Pluto though their instruments? Isn't it time you added this target to your "seen it" list? 

Why not make it a habit to locate this (dwarf?) planet throughout the observing season?  This page contains information for finding the (dwarf?) planet with precise position coordinates, maps, and star-hops. See Charts section below.  

The Pluto Small-Scope Viewing Challenge

 Pluto Links 

Hubble Spots New Pluto Moons!
Amazing images of Pluto's newly discovered moons.
Double Planet Meets Triple Star
(ESO 8.2-m telescope) Images from July 20, 2002 occultation.
Locating Pluto (Peoria Astro Society)
General notes on verifying Pluto in the eyepiece.
Pluto (dwarf?) Planet Profile
Lists up-to-date facts about Pluto.
Pluto (SEDS)
What we know and don't about Pluto and its moon Charon.
Clyde Tombaugh (1906 - 1997)
A site about Pluto and its discoverer, Clyde Tombaugh.
Planet X Song
A ballad about Pluto's discovery and planetary status.


Pluto and Charon: Ice Worlds on the Ragged Edge of the Solar System. This complete book covers the history or Pluto: from discovery, to the realization of its true size, to the discovery of Charon, and current status as "big man" in the Kuiper Belt. 

Beyond Pluto. Pluto and its place in the Kuiper belt. This book is a history of theories and actual discoveries concerning these objects. Discusses how the science "is done" on those mountain-top observatories.

For young readers, try this book from the Isaac Asimov's 21st Century Library of the Universe series.

Much misinformation has been heaped upon the preparatory Pluto observer. The limiting-magnitude "rule-of-thumb" puts the 13.8-magnitude (dwarf?) planet right at the visual limit for 5"/127-mm telescopes, and "common knowledge" says at least an 8"/203-mm scope should be employed for  visual attempts. Yet, a search of the Internet turns up discouraging advice for users of medium-sized amateur telescopes:

"Ignore Pluto. Always ignore Pluto. You can't see it, even with the 10-inch telescope!"
 The University of St. Andrews Astronomical Society website's "What You Can See Now" page for May 2001

"Pluto requires at least a 12-inch diameter telescope and is very difficult to see, even for advanced amateurs."
 Astronomy Resource Site's "What’s Out Tonight?" page (2001).

I can only hope that the comments attributed to the above websites are a reflection of the local observing conditions and not meant as sage advice to observers world-wide.  

On the other end of the debate are reports of Pluto sightings in "impossibly" small instruments. Some attribute this to the power of suggestion: your mind expects to see something in the target zone and does. But, consider this quote from a letter entitled "Pluto in a 4-1/2-inch Scope," that appeared on page-14 of the August 2000 issue of Sky & Telescope magazine:

"What you really need is not a large telescope but a dark sky, some patience, and a little experience with averted vision." 
 Scott Ewart of Philadelphia , PA.

Mr. Ewart took his 4.5" reflector to the Texas Star party in 1999. He met Sky & Telescope contributing editor Stephen James O'Meara, who described sighting Pluto with a 4" refractor in Hawaii. O'Meara urged Ewart to search for Pluto in the little reflector: "After about a half hour of effort, I could say for sure that yes, that's not my imagination, that's it!" 

A search of Internet-based astronomical discussion groups reveals more Pluto sightings, through even smaller instruments. Examine a compilation of such reports in the Visual Sightings Logbook. Counting O'Meara's Hawaiian observation, I've come across two small-scope sightings by well-regarded,  published astronomical authors. I believe this is enough to explode the 8"-scope "rule" for observing Pluto. After all, the dictionary tells us that a rule-of-thumb is "a useful principle having wide application but not intended to be strictly accurate or reliable in every situation." Unfortunately, the 8"-rule has become widely enshrined as an absolute in astronomical circles. Even Mr. Ewart's letter in Sky & Telescope begins by acknowledging the rule: "Too many times to recall, I've read or heard that you need at least an 8- to 10-inch telescope to see Pluto."

Challenge #1: What is the smallest aperture telescope that you can see Pluto in?
Help dismiss the myth: observe Pluto in a sub-8" telescope and spread the word if you succeed. Start by reading the small-telescope Visual Sightings Logbook, to learn how others accomplished this feat. Post your sighting on the Message Board. Users of big scopes have an advantage: they can spot the (dwarf?) planet and then employ aperture masks to determine the aperture cutoff. 

The Pluto Small-Scope Imaging Challenge 
But even if you can't spot the (dwarf?) planet visually, that shouldn't stop small-scope users from imaging the area. CCD or film-based instruments can go to deeper magnitudes than the eye, to capture this little (big dwarf?) planet. 

Challenge #2: What is the smallest aperture telescope that you can image Pluto in?  
What is the point of this Challenge?  Many amateurs are looking for ways to use their equipment to support "real" science, but feel their equipment is too small to provide useful results. As amateur observers, our equipment choices often contend with contradicting needs: good portability versus good aperture. So, based on some "rules of thumb," we must settle on a comprise imaging system that fits these parameters.  As a result, one might be tempted to think: "Oh, I can drive the 30-miles to position myself for the asteroid occultation, but the portable scope I'd use probably won't be able to gather enough light to make imaging worth it."  Maybe it is! 

In the 7-decades since Clyde Tombaugh imaged Pluto, on photographic plates through a large telescope, technology has come a long way. Now, with the right equipment and preparation, the same imaging feat is within the grasp of a back-yard amateur astronomer.

I urge all telescope users to try imaging the (dwarf?) planet some days apart. You can view some sample images here. If you have two (2) images showing Pluto's motion: send the images or URLs here and I'll post or link to them on the Images & Samples page of this challenge. Include details of how the images were made (aperture, camera, image time, location, sky conditions, etc.). I'll post update messages on the Pluto Imaging message area of the message board.

Big scope users, that know they can image the (dwarf?) planet with ease, can try stopping down the telescope aperture with a cardboard mask. See the FAQ for details. How far down in aperture can you go and still capture the (dwarf?) planet?  

Jocelyn Bell Burnell at IAU Pluto meeting
Jocelyn Bell Burnell at the IAU meeting makes a presentation to the august body on the August day that Pluto was voted out of the planet club.
--IAU/Lars Holm Nielsen

Star Charts Throughout the Pluto Season
Now you'll need to examine the view in the main telescope to verify the (dwarf?) planet, with the aid of a detailed chart. As you narrow down the (dwarf?) planet's location with these charts, switch to higher-power eyepieces to limit the view and separate the faint (dwarf?) planet from the field stars. 


  • Sky & Telescope publishes an article and map for locating the outer planets every year. Stars to 14-mag are typically shown.  
  • Royal Astronomical Society of New Zealand has Pluto charts for southern hemisphere observers.   

More Chart Resources

  • The yearly Astronomical Calendar by Guy Ottewell, usually has a photographic star chart marked with Pluto's locations over the course of several years. 
  • If you need to examine the area in greater detail, use a good photographic chart from an online atlas such as the STScI Digitized Sky Survey.

Pluto Deadline 
Don't wait-out the year to start your observing!  The (dwarf?) planet will be setting soon after sunset in October and lost in the solar glare soon after.

Northern observers shouldn't put off observing this (dwarf?) planet. For them, Pluto was highest in the sky in the year 1980!  The (dwarf?) planet has been heading toward the descending node of its solar orbit ever since -- it will be lower to the horizon each passing year. Also, the (dwarf?) planet's orbit will position it against ever denser areas of the Milky Way. With more stars in the field of view, "on the spot" detection will be harder, but detection at very-high power by motion comparison will be easier.  

Revision Notes:

06/14/2009 Challenge page updated for 2009.
07/15/2007 Challenge page updated for 2007.
06/11/2006 Challenge page updated for 2006.
07/08/2006 Pluto occultation and moon names update
07/24/2006 Added Douglas W. Neal image to "Reference" section of "Results" page.
08/12/2006 Added August to mid-October chart in "Charts".
08/24/2006 Added update on IAU vote on planetary status.
03/11/2007 Changed planet to (dwarf?) planet

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