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Welcome again to our monthly newsletter with features on exciting celestial events, product reviews, tips & tricks, and a monthly sky calendar. We hope you enjoy it!

• A Strange Day on Mercury
  Where a day is longer than a year.
     
• Barlow Lenses
  Geoff Gaherty explains, compares and contrasts several of these helpful lenses.
     
• High School Astronomy: Giving Back to the Field
  Dr. Larry Krumenaker reports back on a survey he conducted (in part) through Starry Night Times three years ago.
     
• Starry Night® File of the Month
  The Magellanic Clouds.
     
• Constellation in Focus: Auriga
  This faint winter constellation holds three Messier jewels.
     

Mercury is the closest planet to the Sun, never straying more than 28 degrees from it. Because of this, it is difficult to see much detail on this planet from the surface of the Earth. Early observers in the 1800’s used this meagre information to deduce a rotation rate of 88 days. This would make one side of Mercury always face the Sun while the other side would be in constant darkness.

It wasn’t until 1965 that it was determined that Mercury’s actual rotation rate was 58.646 days. Now this turns out to be exactly 2/3 of the 87.969 day orbital period so Mercury rotates 1.5 times in one “Mercury” year. This gives rise to a rather strange phenomenon — a solar day on Mercury is longer than a year!

The left graphic shows sunrise on Mercury on January 5 and the right graphic shows the next sunrise on June 29 — that’s 176 days, or twice the 88 day orbital period! To see another sunrise on Mercury you would have to wait 2 Mercury years! Furthermore, “daytime” and “nighttime” on Mercury would each last about one Mercury year.

This difference between the rotation period and the solar day is true for all planets including the Earth. But because the Earth rotates much faster (and is farther away from the Sun) than Mercury — 23h 56 m — its solar day is only 4 m longer at 24 h. For the rapidly rotating Jupiter the difference is only a few seconds.

But that’s not all. Because of its highly eccentric orbit, Mercury’s orbital velocity increases significantly as it approaches perihelion. A few days before perihelion the angular orbital velocity equals Mercury’s angular rotational velocity. As a result, the rising Sun appears to stop in Mercury’s sky as time progresses. Then, as the orbital velocity increases, the Sun actually reverses its path in the sky before resuming its normal westward path. If you are at the right place at the right time you can actually witness a double sunrise!

You can explore Mercury’s strange days yourself by opening the file <Sun_Path.snf> in your Starry Night program. Let time Run Forward and watch the Sun’s antics as it rises above Mercury’s surface.

Herb Koller

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The Barlow lens was invented by British physicist and mathematician Peter Barlow (1776–1862).

Barlow got the idea to introduce a negative lens just in front of the eyepiece of a telescope. This increased the effective focal length of the telescope, or, to put it differently, the magnification of the eyepiece. Barlow used a single double concave lens.

Because this introduces chromatic aberration, most modern Barlow lenses use two or more elements to make them achromatic (color free).

Most Barlow lenses are "universal" and can be used with any telescope or eyepiece. So-called "long Barlows" use a fairly long focal length lens and are mainly for reflectors.

Because of their long tubes, “long Barlows” don’t work well if they need to be fitted into diagonals, commonly used on refractors and catadioptrics. To accommodate these scopes, “short Barlows” were developed using a shorter focal length lens. This places greater optical strain on the system.

Here’s a side-by-side comparison of the two sizes:

Since a Barlow lens will be used with a number of different eyepieces over a long period of time, it's worth buying a good quality one. The best of the "short Barlows" is the Orion Shorty Plus (show above on the left).

The best "long Barlows" are the Orion Ultrascopic (shown above on the right) and the TeleVue 2x.

Avoid 3x Barlows and “zoom” Barlows, as any 2x Barlow can easily give more magnification by increasing the distance from Barlow to eyepiece (slide the eyepiece out a bit). A popular trick for increasing the magnification of a 2x short Barlow in a refractor or catadioptric is to place the Barlow between the diagonal and the telescope, rather than between the eyepiece and the diagonal.

In a different league entirely are Tele Vue's Powermates. These work similar to a Barlow lens but have a more sophisticated optical system which eliminates some of the problems with ordinary Barlows.

A Barlow lens is often recommended as an early purchase for new telescope owners because it instantly doubles the beginner’s small eyepiece collection. Strangely enough, most experienced amateur astronomers rarely use Barlows, preferring the simplicity of modern eyepieces with built-in Barlows like Tele Vue Radians and the Orion Stratus and Edge-On Planetaries.

One use for which Barlows and Powermates have become very popular in recent years is in imaging the planets with planetary cameras, such as the Orion StarShoot Solar System Color Imager III. This enlarges the image scale without introducing the aberrations found in eyepiece projection.

Geoff Gaherty
Geoff has been a life-long telescope addict, and is active in many areas of visual observation; he is a moderator of the Yahoo "Talking Telescopes" group.

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Exactly three years ago, this newsletter sent out a request for volunteers to complete a survey of high school astronomy programs. Quite a few of you responded and helped us to complete the first survey of this scale in the field since the 1980s. We looked at:

• Who was teaching high school astronomy — the number of high school astronomy teachers in each school, their background and training and the courses they teach;
   
• Who takes astronomy — the demographics of the students in these courses, the average class size and grade levels involved;
   
• The courses themselves — curriculum covered, prerequisites, materials used, e.g. textbooks, telescopes, planetariums;
   
• Advice current high school astronomy teachers would give to those who want to create such a course, including how to keep up — which magazines and websites they use, which conferences are helpful;
   
• What effects No Child Left Behind (NCLB) has had on astronomy courses;
   
• Teachers’ views of the future of astronomy programs and their opinions on why such courses are valuable.

I am the fellow who sent out the initial request and from it came a doctoral dissertation. I now want to give back a little to those who generously assisted with my research.

In total, three surveys were completed, two of high school astronomy teachers and one for principals of schools without astronomy programs. The first one became the bulk of the dissertation. The abstract reads as:

A spring 2007 nationwide survey of high school astronomy teachers investigated: how many high schools teach astronomy, teacher backgrounds, student demographics, classroom materials and facilities and other facets of the modern course. Comparisons were made to Philip Sadler’s 1986 survey and to various states’ Departments of Education data. This multimethods study included qualitative questions investigating teachers’ perceptions about effects from 2001’s No Child Left Behind Act (NCLB) on their classes, views of course futures in their schools, and the nation. Other questions solicited their community wisdom on starting a course, defending it, and what needs to be done to increase their number.

Significant conclusions include: the number of regular classes are about 3200, totaling up to 4000 when a ‘hidden’ single-digit-sized classes population is added in; fully 20% of all classes may be with 10 or fewer students. A course is found in 2500 schools, 12-13% of all U.S. high schools.

Many of Sadler’s numbers are unchanged in 22 years. However, the ratio of male to female teachers has gone from 88:12 to 67:33. Many teachers now come from the bioscience and geoscience majors, not physics. We tally 3-4% more schools now than Sadler, and nearly twice the teachers (3200).

Schools with astronomy are more often Passing in Adequate Yearly Progress (AYP) than the national norm. Classes generally reflect racial, gender and ethnic demographics of their schools and the nation.

More than half of all teachers claim no direct effects from NCLB on their courses, most of the rest seeing negative effects, generally dependent on how other science, math and language courses fare.

A growing number supplant conventional planetariums with computer "planetarium" software, currently at the same rate as portables ownership.

Twenty-eight percent of teachers are not ‘highly qualified’ in that they have never had an astronomy course, let alone an astronomy degree.

Teachers are generally more optimistic than pessimistic but their optimism is mostly for their school, not for the fate of courses around the nation.

A six-part plan for starting a class is developed and six defensive arguments are also offered.

Some additional notes: there has been at least one direct effect of the NCLB program on astronomy education: teachers, including some who have taught high school astronomy for decades, have lost their positions because they are not considered “highly qualified,” a status which is difficult to attain, as not one state offers teacher certification in astronomy. Too, planetariums, considered irrelevant to a schools Adequate Yearly Progress score, are being shut down.

To improve the statues of astronomy education in high schools, I conclude that the following efforts should be made:

• Raise perception of the value of astronomy education among all levels of administration — from school principals to state and federal departments of education;
   
• Demonstrate the multidimensional and interdisciplinary nature of astronomy education, as well as the inherent opportunities for hands-on and life-long learning experiences;
   
• Increase astronomy content in state standards and standardized testing;
   
• Attract and retain more fully qualified educators — not only the willing and enthusiastic, but those who are trained in astronomy and astronomy education. Greater training is the highest priority;
   

For those who want all the gory details, several articles have appeared in the scholarly journals Astronomy Education Review (AER), The Planetarian (specifically on the subset of high school teachers of astronomy with planetariums), and in The Science Educator (on the effects of No Child Left Behind on astronomy courses). A further article, on the survey of principals, will be online at AER by the time this Starry Night article is distributed. I think it is most important because it contains a prescription for increasing the profile of astronomy in high schools. You may find all of these articles online at hermograph.com/highschool/highschoolastronomy.htm.

The next step is to apply these findings toward practical change. As our teachers have expressed a need for a purely astronomical, practice-oriented publication, I have created The Classroom Astronomer, a quarterly magazine for teachers of astronomy, whether they use planetariums, software, or just blackboards on a wall. You can look at the magazine and download the first issue for free at classroomastronomer.toteachthestars.net. Later this year, all of the material about how to create, run, and defend a course from high stakes testing and NCLB will be released in a book by Hermograph Press.

I gratefully thank all those Newsletter readers who answered my call in 2007 and wish all readers success in their astronomical endeavors, educational and otherwise.

Dr. Larry Krumenaker

To Teach The Stars Network
2897 N. Druid Hills Road, Suite 325
Atlanta, GA 30329
404 702 8147
Fax: 404 393 7037
www.ToTeachTheStars.Net
Larryk@ToTeachTheStars.Net

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Magellanic Clouds

• MagellanicClouds.snf

The Large Magellanic Cloud (LMC) is one of the closest galaxies to our own Milky Way, being only 180,000 light years away, and closer than its companion galaxy, the Small Magellanic Cloud.

The Large Magellanic Cloud has an irregular shape and no central core, probably because of the gravitational attraction of the Milky Way, which is 10 times the size of the LMC.

The LMC encompasses several degrees in the sky and can be easily seen with the unaided eye by observers in the Southern hemisphere. However, it was unknown to Europeans until the voyage of Portuguese explorer Ferdinand Magellan in 1519.

Pedro Braganca
Education & Content Director
Starry Night® Education

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Auriga is most notable for its three bright open clusters and for sporting one of the ten brightest stars in the night sky, Capella.

In ascending order of interest are Auriga's three Messier-designated open clusters: M36, M38 and M37. All are clearly visible to the naked eye from a dark site and, in binoculars, appear as bright fuzzy patches; naturally, a telescope brings out the most detail. M36 will show around 50 stars in an 8" scope while M38 shows twice as many stars, some in apparent chain-like arrangements. But the most notable of the trio is M37. In a 12" scope, roughly 150 starts are visible in this neatly arranged cluster, some tinged red.

NGC 1931 is a bright emission nebula surrounding a very small open cluster. With high magnification in an 8" telescope, the nebula is quite apparent.

Sean O'Dwyer
Starry Night® Times Editor

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