But this time… Missing our 9th planet

IAU 2006 General Assembly: Result of the IAU Resolution votes

24 August 2006, Prague

The first half of the Closing Ceremony of the 2006 International Astronomical Union (IAU) General Assembly has just concluded. The results of the Resolution votes are outlined here.

It is official: The 26th General Assembly for the International Astronomical Union was an astounding success! More than 2500 astronomers participated in six Symposia, 17 Joint Discussions, seven Special Sessions and four Special Sessions. New science results were vigorously discussed, new international collaborations were initiated, plans for future facilities put forward and much more.
In addition to all the exciting astronomy discussed at the General Assembly, six IAU Resolutions were also passed at the Closing Ceremony of the General Assembly:

1. Resolution 1 for GA-XXVI: “Precession Theory and Definition of the Ecliptic”
2. Resolution 2 for GA-XXVI: “Supplement to the IAU 2000 Resolutions on reference systems”
3. Resolution 3 for GA-XXVI: “Re-definition of Barycentric Dynamical Time, TDB”
4. Resolution 4 for GA-XXVI: “Endorsement of the Washington Charter for Communicating Astronomy with the Public”
5. Resolution 5A: “Definition of ‘planet’ “
6. Resolution 6A: “Definition of Pluto-class objects”

The IAU members gathered at the 2006 General Assembly agreed that a “planet” is defined as a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.
This means that the Solar System consists of eight “planets” Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. A new distinct class of objects called “dwarf planets” was also decided. It was agreed that “planets” and “dwarf planets” are two distinct classes of objects. The first members of the “dwarf planet” category are Ceres, Pluto and 2003 UB313 (temporary name). More “dwarf planets” are expected to be announced by the IAU in the coming months and years. Currently a dozen candidate “dwarf planets” are listed on IAU’s “dwarf planet” watchlist, which keeps changing as new objects are found and the physics of the existing candidates becomes better known.
The “dwarf planet” Pluto is recognised as an important proto-type of a new class of trans-Neptunian objects. The IAU will set up a process to name these objects.
Below are the planet definition Resolutions that were passed.
Notes for editors
A press conference about the Closing Ceremony of the General Assembly, including the results of the planet-definition vote, will be held at 18:00, in Meeting Room 3.3 of the Prague Congress Center. (It will NOT be possible for journalists to ring in to this conference: they must be there in person.)
The panel for the press conference will be:

• Ron Ekers (outgoing IAU President)
• Catherine Cesarsky (incoming IAU President, Member of the Planet Definition Committee)
• Jan Palous (Chair of the National Organising Committee)
• Richard Binzel (Member of the Planet Definition Committee)
• Karel van der Hucht (incoming Secretary General)

This press conference will conclude around 18:30 CEST.
The IAU is the international astronomical organisation that brings together distinguished astronomers from all nations of the world. Its mission is to promote and safeguard the science of astronomy in all its aspects through international cooperation. Founded in 1919, the IAU is the world’s largest professional body for astronomers. The IAU General Assembly is held every three years and is one of the largest and most diverse meetings on the astronomical community’s calendar.

Seven years before, She kept her status

The Status of Pluto: A Clarification

IAU Press Release 01/99

February 3, 1999

Recent news reports have given much attention to what was believed to be an initiative by the International Astronomical Union (IAU) to change the status of Pluto as the ninth planet in the solar system. Unfortunately, some of these reports have been based on incomplete or misleading information regarding the subject of the discussion and the decision making procedures of the Union.

The IAU regrets that inaccurate reports appear to have caused widespread public concern, and issues the following corrections and clarifications:

1. No proposal to change the status of Pluto as the ninth planet in the solar system has been made by any Division, Commission or Working Group of the IAU responsible for solar system science. Accordingly, no such initiative has been considered by the Officers or Executive Committee, who set the policy of the IAU itself.

2. Lately, a substantial number of smaller objects have been discovered in the outer solar system, beyond Neptune, with orbits and possibly other properties similar to those of Pluto. It has been proposed to assign Pluto a number in a technical catalogue or list of such Trans-Neptunian Objects (TNOs) so that observations and computations concerning these objects can be conveniently collated. This process was explicitly designed to not change Pluto’s status as a planet.

   A Working Group under the IAU Division of Planetary Systems Sciences is conducting a technical debate on a possible numbering system for TNOs. Ways to classify planets by physical characteristics are also under consideration. These discussions are continuing and will take some time. The Small Bodies Names Committee of the Division has, however, decided against assigning any Minor Planet number to Pluto.

3. From time to time, the IAU takes decisions and makes recommendations on issues concerning astronomical matters affecting other sciences or the public. Such decisions and recommendations are not enforceable by national or international law, but are accepted because they are rational and effective when applied in practice. It is therefore the policy of the IAU that its recommendations should rest on well-established scientific facts and be backed by a broad consensus in the community concerned. A decision on the status of Pluto that did not conform to this policy would have been ineffective and therefore meaningless. Suggestions that this was about to happen are based on incomplete understanding of the above.

The mission of the IAU is to promote scientific progress in astronomy. An important part of this mission is to provide a forum for debate of scientific issues with an international dimension. This should not be interpreted to imply that the outcome of such discussions may become official IAU policy without due verification that the above criteria are met: The policy and decisions of the IAU are formulated by its responsible bodies after full deliberation in the international scientific community.

Johannes Andersen
IAU General Secretary (1997-2000)

Canon EOS 70-200mm L Lenses

小白阿小白！你怎么能这么贵呢…..

http://www.photo.net/equipment/canon/70-200

by Philip Greenspun

You cannot be a professional photographer without a high-quality, high-speed telephoto zoom lens. Within the Canon EOS system, three such lenses are available:

• 70-200/4L
• 70-200/2.8L
• 70-200/2.8L image-stabilized

All of these provide very high image quality. All have ultrasonic motors and allow for full-time manual focus. This article is intended to help you decide among these three lenses.

Portraits

The f2.8 aperture is essential to throw the background out of focus, especially for portraiture at around 100mm. Note that the Canon L zooms are probably too sharp for flattering glamour portraits of most people without either professional makeup at exposure time or a little PhotoShop afterwards.

Ruggedness

I was covering the IMTA convention in Manhattan, where several thousand aspiring fashion models converge on the Hilton with their agents/handlers/schools (hoping to be discovered by agents in Japan, Europe, and maybe even New York).

Ben, one of my 18 y.o. students from MIT the preceding semester, had to leave New York that week and, his going-away present was to come along as an assistant on this job. [I think he was satisfied; as we waded through the sea of 14-17 y.o. flesh at the juniors swimsuit competition, I had to repeatedly hoist his tongue back into his mouth.]

Every now and then we’d find a really beautiful contestant and drag her outside for better light. This usually attracted a crowd. At one point, I decided to change the 70-200/2.8L for a 50 macro. I started to unmount the 70-200 and then realized the camera bag wasn’t open. In the back of my mind, I didn’t trust Ben to do anything so I moved my hands to open the camera bag. The month-old 70-200/2.8L (non-stabilized) dropped from waist height (1 meter) onto concrete with a horrifying “thunk”.

No damage. [Of course, the gods punished me for writing the above. In October 1997, I was in Northeast California and the lens became hard to focus manually (but was fine in AF mode). A couple of days later, I noticed that the front and back halves of the lens were no longer securely connected. It went to Canon for a $100 worth of service and I’m still using the lens in 2001.]

AF Speed

Autofocus with these lenses is nearly instant. This makes the 70-200s great lenses for street photography, even if somewhat obtrusive. Despite the lenses’ near-instantaneous focusing, Canon included a focus range switch. The settings are “1.5m to infinity” and “3m to infinity”. In theory, if you were photographing lions in Africa, you’d want the 3m-infinity range set so that when the camera lost focus it would spend less time hunting. In practice, what happens is that I always knock the switch to the 3m-infinity range by mistake. Then I’m photographing my friend’s kid on a carousel and wondering why continuous AF tracking is working so poorly. I waste about five frames before I think to take my eye away from the camera and reset the AF range switch. Canon bodies should have a custom function to disable these lens switches but they don’t.

Above images were taken with continuous AF, EOS-5 body set to choose by itself among the 5 AF sensors. Non-stabilized 70-200/2.8L. Fuji Super G + 400 neg film..

Handling

You turn a ring to zoom this lens. If you have the lens on a tripod pointing down a bit, that means that the focal length doesn’t creep as it would with a push-pull zoom. Much nicer. The Canons also come with a removable tripod collar. The bayonet plastic lens hoods work well also.

Oh yeah, the image quality

These lenses are so good in terms of flare, contrast, and sharpness that it is tough to find anything to criticize. However, if you look at Lens Work II, the book of optical formulae published by Canon, it is pretty clear that any of the prime telephotos (including special-purpose lenses like the 100 macro and the 135 SF) outperform the 70-200 in terms of modulation transfer function (resolution/contrast). So if you are obsessive about image quality, you can save yourself a lot of cost and weight by going with an 85/1.8, 100/2, 100 macro, 135/2.8SF, 135/2L, 180 macro, 200/1.8, or 200/2.8.

Teleconverter Compatible

Unlike its 80-200/2.8 predecessor, all of the Canon 70-200 L lenses are compatible with the Canon 1.4X and 2X teleconverters. The photo at right was taken with the 70-200/2.8L and 1.4X converter (Kodak E100 film, EOS-5 body, ARCA Swiss ballhead on Gitzo carbon fiber tripod). Note that the resulting effective 300mm lens wasn’t really long enough for this medium-sized animal, even though his home is the Seattle Zoo. Image quality is quite high though you are definitely going to lose a lot of sharpness with a 2X converter.

How Well Does Image Stabilization Work?

Our first tests of the 70-200/2.8L IS lens were very encouraging. Here are some images taken with a Canon D30 body, standing up, with the zoom set to 200mm, of a building in New York City:

	unstabilized	stabilized
1/15th
1/30th
1/60th

Here are some images taken while sitting down of a flower, also at 200mm:

1/15th	1/30th	1/60th

The bottom line seems to be that acceptable results are obtainable at 1/30th of a second. That’s 3 f-stops better than you’d expect from the “1/focal-length” rule of thumb.

Deciding Among the Versions

If you’re going backpacking with a tripod, save your back and get the 70-200/4L. For studio portraits that will be lit by electronic flash, get the 70-200/2.8L (non-stabilized). For all-around high-performance, you definitely want the IS version of the 70-200/2.8L.

Only if you’re on an extremely tight budget should you consider the anicent Canon EOS 80-200/2.8L lens. This lens does not allow for full-time manufaul focusing. Also, the old lens design also is incompatible with teleconverters.

• 2.8L
• 2.8L IS
• 4L

Gallery

I like using the 70-200 on a tripod to isolate patterns in landscapes. I’ll have the lens stopped down to at least f/11 for wide depth of field but I still appreciate the f/2.8 maximum aperture because it keeps the viewfinder bright and makes it easy to focus manually.

Here are some snapshots from my excursions to foliage country…

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