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An electronic publication of The West Hawaii Astronomy Club -

Club Officers:

President:
    Doug Summers

Vice President:
    Craig Combes

Secretary:
    Craig Nance

Treasurer:
    

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W. M. Keck Observatory



This website is currently maintained by
Doug Summers

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E-mail: whacmail@yahoo.com

 


March 2007 Club Meeting Report



Agenda:

Welcome/Introductions Pierre Martin    5 Minutes
The Sky this Month Pierre Martin 15 Minutes
Messier Marathon Debate! A Cooper / D Summers 20 Minutes
Social Break All 10 Minutes
Featured Talk - OHANA Olivier Lai 35 Minutes
Club Business Doug Summers 15 Minutes




The WHAC Meeting was held on March 13, 2007 at the Canada France Hawai'i Telescope conference room in Waimea.

Pierre Martin, our CFHT sponsor, facilitated the meeting. There were about 28 folks in attendance. The meeting started with introductions of the new faces. There were 3 or 4 new folks including a visitor from Pennsylvania, Louis Berman, who is out visiting the Mauna Kea observatories in his quest to visit "every notable observatory".

Pierre presented The Sky this Month in a slightly different format. He wanted to focus on a particular constellation, Leo. He presented what the solar system is doing in March:
  • march 4 was the full moon, the Bebookwaadaagame-glizis moon - a Native American term for "crusty snow moon"
  • this is a good time for Saturn viewing as the tilt is decreasing. By 2009, the tilt will be almost flat, with the rings almost invisible to us.
  • the sun has been very quiet, with almost no prominences or spots
Moving on from the solar system, Pierre discussed comet Encke, with the shortest period of all comets, just about 4 years. It will be visible in the constellation Aries in April. However, the highlight of March is the galaxies available in Leo. The constellation is large - only about 5 constellations are bigger. Galaxies are so prevalent in Leo primarily because of its position in the galaxy with respect to us on the Earth, and the Sun. Leo lies close to the northern galactic pole of the Milky Way, and above our sun. So, there are not a lot of stars, dust, nebulae in that area, but lots of galaxies. A few of the interesting objects to see in Leo are:
  • Regulus is actually a triple star in Leo
  • Lots of binary star systems in Leo, including Gamma Leonis and 88Leo
  • A challenge to the astronomers: Wolf359 is the smallest star known. The third closest to our sun, it is a red dwarf (M6 class) star that is just 13.5 magnitude, but famous in science fiction stories.
  • A tour of some of the best galaxies was provided, using gorgeous pictures taken by amateur astronomers - M65, M66, M95, M96, ... the Leo Triplet, and even Leo I - not much of a galaxy overshadowed by the star Regulus.

A light-hearted Messier Marathon debate was next on the agenda. New member and self-proclaimed Messier Marathon advocate, Andrew Cooper, began the discussion with his experiences in Arizona. Last year, they had 25 people all get the whole 110 objects during their marathon. Andrew's reasons why people should participate in the marathon are:

  • It's fun!
  • It's a good test of your skills as an observer
  • It's good practice

Doug Summers then presented the other side of the argument, "Don't waste your time!" Doug contended that ~10% of the objects are just "ugly" and another 10-15% are on the horizon, so therefore about 25% of the objects in the marathon are not worth the effort it takes to look at them. Doug suggested that if you want to do a marathon, create your own list, or honor Herschel instead.

The "debate" ended with both sides agreeing that it's great fun to do a Messier Marathon! So, come join the club this weekend at the dark site. It will be the for the most favorable weekend at almost the optimal latitude.

We had a short break before the featured talk of the evening, Olivier Lai of CFHT presented details about the 'OHANA project. 'OHANA is an acronym for Optical Hawaiian Array for Nanoradian Astronomy. Olivier described how astronomers are always anxious for bigger telescopes for fainter and fainter objects. However, there are diminishing returns for resolving power in attempting to build ever-larger telescopes. To solve some astrophysical problems requires much more resolution, not necessarily more light gathering. To get this resolution, you need different techniques. 'OHANA uses interferometry between multiple, widely-separated telescopes to get better resolution.

Olivier spent some time introducing adaptive optics (AO) as a coupled technology to interferometry. Atmosphere distorts the photons coming to Earth, so we need to use space telescopes, or correct in real-time. Space telescopes are expensive and have small apetures. Correcting in real-time is limited by having bright natural guide stars close to our objects of study. 'OHANA will correct in real-time, using adaptive optics techniques. Olivier went through a very good overview of how adaptive optics works.

Olivier discussed the concept of diffraction. Diffraction was discussed as a wave phenomena. A variety of diffraction effects were illustrated, and their application and utility in interferometry were discussed. A variety of different telescope pupils and rotation angles were used to show the concept of a Point Spread Function (PSF). Different telescopes and pupil sizes can be used together; just the PSF changes. The different pupil sizes of the various telescopes on Mauna Kea actually works relatively well as far as the combined PSF is concerned. Several interesting interferometric baselines can be used for valid scientific studies.

Mauna Kea is the largest site of optical telescopes with AO systems. 'OHANA is a multinational collaboration to combine the light from several of the observatories on Mauna Kea interferometrically, using 85m to 800m baselines. The master plan on Mauna Kea does not allow for any more development, so 'OHANA is using fibers to move the light between the telescopes on Mauna Kea. The first proof-of-concept was coupling the light of the two Keck telescopes via single-mode fibers, reported in Science magazine. Currently, Olivier and his team are building delay lines at CFHT for combining light from CFHT and Gemini telescopes in the next phase. There is a long way to go, with more and longer baselines (using other telescopes on Mauna Kea), better fibers for more wavelength coverage, and even harder problems like how to schedule time on such an instrument. This project is full of interesting challenges! If successful, 'OHANA will be the largest optical interferometer with no competition for the forseeable future.

Doug quickly skimmed through the club business. There was a sponsor/leadership meeting a couple of weeks ago at which they discussed the state of the club. 2006 was a good year for the club - membership is about 90 people, the budget is in good shape, the media communications are good. They decided to modify the leadership from a co-presidency of three, to a president/vice-president/secretary/treasurer.
The new leadership is:

  • President Doug Summers
  • Vice President Craig Combes
  • Secretary Craig Nance
  • Treasurer Neil Paulsen
The vision for 2007 includes:
  • increased the media announcements; plan further ahead so the announcements in the media can be more detailed
  • better attendance at the observing sessions
  • growing the leadership and participation at the meetings
  • hosting a public star party
  • remaining a "dues free" organization
Doug finished by again thanking our sponsors, CFHT and Keck Observatory!

The weather forecasts are getting better for the weekend, so plans are to observe at the WHAC Dark Site this weekend. Check the WHAC Yahoo groups page for the latest news and information as the weekend approaches.

.

The next WHAC meeting will be in the Keck Hualalai Conference Room on Tuesday April 10, 2007 at 7pm. The meeting agenda will be on the WHAC web site soon. As always, at ~6pm prior to the meeting everyone is invited to join in on a pre-meeting social at the Parker Ranch Food Court!




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February 2007
January 2007
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October 2006
September 2006
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1992 Mauna Kea Astronomical Society Newsletter



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