Safety while using a telescope to view a total solar eclipse

Safety while using a telescope to view a total solar eclipse

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I have an 8-inch reflector telescope and a solar filter that goes on the front aperture to view the Sun (most recently to view the transit of Mercury). If I were to use this telescope during a total solar eclipse, would it be safe to remove the filter during totality? Let's assume I also get the filter back on before totality ends.

Yes, you can remove the solar filter during totality - otherwise you will have no way to see the corona (or anything at all) through the telescope during totality.

The dangerous time is (as you also say yourself) towards the end of totality - and it's easy to get lost in time and the joy of the moment. Set a timer to wake you seconds before end, have others observing with you do the same. You absolutely must put back the filter in time prior to end of eclipse or risk your eye sight looking through. If you (only) use it to take images, it's not as critical as it's not your eye being fried but your camera, but don't go beyond diamond ring without filter and camera attached either.

Thus either case: Put back the filter preferentially before the end of eclipse.

11:30-1:30 Monday, August 21 at Shenk Sports Complex (South of Park and Ride Lot 301)

On August 21, 2017, Lawrence, Kansas, will be in the path of a solar eclipse. It’s estimated that 99.3% of the sun will be blocked. Join the KU Department of Physics and Astronomy and the KU Natural History Museum at the Shenk Sports Complex to view the eclipse and learn more about this solar phenomenon when it peaks at about 1:07 pm. Free eclipse glasses will be provided.* The family-friendly, drop-in event includes science and art activities with the Spencer Museum of Art, the KU Natural History Museum, and the Lawrence Public Library. And, of course, telescope viewing with astronomers.

At that venue, various ways to safely view the sun before, during and after the deepest part of the eclipse will be available to visitors, including safety glasses and specially designed telescopes. It is important to know that even with the sun covered more than 99%, it is NOT safe to look directly at the sun without specially designed equipment or appropriate safety glasses. The eclipse glasses we are able to provide have been provided by the American Astronomical Society and Google, the University of Kansas and the Department of Physics & Astronomy for your safe use.

The following food trucks will be selling their wares, as the viewing event will take place during lunchtime:
Ad Astra Food Truck
Kona Ice
Torched Goodness

What to bring:
Blanket or lawn chair
Sunscreen and a hat
Cash for the food trucks
A sense of wonder

*Remember, it’s never safe to look at the sun, even with regular sunglasses. To safely view the eclipse, you will need special eclipse glasses.

If you aren't joining us at Shenk, where can you get Eclipse Glasses on KU's Campus on Monday, August 21?
Here is the complete list of venues. Distribution is 8:30-10:30 a.m. or until they are gone!

Capitol Federal Hall
DeBruce Center/KU Info
Eaton Hall/LEEP2
Green Hall
Joseph R. Pearson Hall
KU Dining (distribution begins at breakfast and will go until all glasses are gone)
KU Parking
Natural History Museum
Nunemaker Hall
Pharmacy Building
Stauffer-Flint Hall
Student Affairs Welcome/Info Tables in front of Wescoe Hall and Strong Hall
SUA Info Booth at Kansas Union
Kansas Athletics

Concern regarding Counterfeit Eclipse Glasses

In recent days, there has been concern over counterfeit glasses being available through various outlets. The American Astronomical Society has issued a statement regarding this problem.
You should only be able to see the sun through proper eclipse glasses. If you can see anything other than the sun, or there is a tear or scratch on the lens, or the lens is coming apart from the paper frame, throw the glasses away. They will not protect your eyes properly during the eclipse.

MU observatory hosts viewing party for partial solar eclipse, prepares for total eclipse

A partial solar eclipse on Thursday has people looking forward to a total solar eclipse in the coming years.

MU Department of Physics and Astronomy hosted a viewing party Thursday afternoon at Laws Observatory so the community could catch a glimpse of the partial solar eclipse.

Ten-year-old Samuel Kingsley was at the event with his family and said he’s seen a blood moon before, but never a solar eclipse.

“It looked like someone bit the corner off the sun,” he said.

Samuel was just one of over 50 people who came out to watch the eclipse.

Director of Astronomy and Professor of Astrophysics Angela Speck helped organize the event and said she was happy with the turnout considering the weather.

“With it this cloudy, I’m impressed with how many people have come up here,” she said.

The eclipse started around 4:40 p.m. and lasted until the sun went down around 6 p.m. The sun could be seen off and on through the clouds.

The observatory offered telescopes with solar filters and special glasses for people to wear so they could watch the eclipse without hurting their eyes.

Speck said while partial solar eclipses are rare, she’s looking forward to an even more rare event happening over Columbia soon.

“Just under three years in August of 2017 there will be a total solar eclipse that comes right over Columbia,” Speck said. “We have actually convinced the Athletics Department, thank you Mike Alden, to let us use Faurot Field. So we will have an event where people will get to come and watch that whole event there and that’s when the moon will really cover the sun and we’ll see the whole thing.”

Welcome to the DAS!

We have made the decision to extend the cancellation of all indoor DAS events because of concerns about COVID-19 (Coronavirus) until further notice. The cancellations include Public Nights, Open House, In-Reach, and VNH Scholarship Committee meeting. Public Night reservations for all months will be blocked.

Members-only access to the DAS Dark Site on Dark Sky Weekends will be determined by lottery. There will be Site Orientations by lottery on Saturday after E-Board. (See the Event Page on the Member Portal for information.) See the Dark Site page for information about dates. Use of the Dark Site at other times will be restricted to 25 people at a time. If you arrive and there are already 25 people at the site, please return home.

The monthly E-Board meeting and General Meetingswill continue to be held via conference call or ZOOM instead of in-person. All members are welcome to attend these meetings, and conference connection information will be provided as the time approaches.

While we are extremely disappointed that we cannot continue with these events as planned, we believe this is the right decision given the current circumstances.

We are monitoring the situation closely and will make further decisions in the coming days and weeks as appropriate. We will continue to review our guidance based on official advice.

DAS Members: Please check the Member Portal or our website, for updates, which will be posted as the situation evolves. Questions may be directed to [email protected] .

– Your Denver Astronomical Society Executive Officers

One of the Nation’s Largest and Most Active Astronomical Societies, Since 1949!

Solar Observing on Space Day 2015

The Denver Astronomical Society (DAS) promotes the enjoyment and understanding of astronomical phenomena, history and lore by providing educational and observing opportunities for our members, education to the general public, and outreach activities at the University of Denver’s Historic Chamberlin Observatory, schools, and nature centers.

WHAT’S UP (for those hungry for the latest astronomy information !)

  • The latest information on astronomy and space exploration can be found on the DAS Twitter and Facebook pages.
  • For detailed information on the latest Astronomical discoveries, see the monthly DAS Astro Update
  • Five Nights in the Magellanic Clouds, a tour of the southern sky by astronomy writer Jeff Kanipe.


DAS monthly meetings (Now accessible only online via ZOOM) feature outstanding presentations on a wide array of astronomical and space-science topics and are open to the public (except for society functions in March and December.) Videos of DAS monthly meetings are posted on our YouTube Channel

Media Inquiries : please contact our Media Coordinator via Email HERE.

DAS member “In-Reach” events provide new members and those new to astronomy with information on telescopes, astronomical equipment, and observing techniques during “hands-on” opportunities at DU’s Historic Chamberlin Observatory and the DAS Dark Site.

Our Edmund G. Kline Dark Site on the Eastern Plains near Deer Trail, Colorado provides dark skies for members. At the present time, a lottery system is being used to comply with state guidelines for social distancing.

Our online Member Portal provides easier access to membership and donation options as well as Member Forums that improve communications among members with special interests in space science and astronomy. The Classified section of the Portal is open to non-members who wish to purchase used astronomy equipment from DAS members.

(NOTE: Public Nights have been suspended until further notice due to COVID-19) The society’s volunteer members conduct public and education outreach activities that reach over 6,000 children and adults each year, that include twice-weekly public observing nights and monthly open house star gazing nights at Chamberlin Observatory and external outreach activities at local schools, businesses and institutions. The DAS also hosts events to access special astronomical phenomena such as eclipses, comets, close planet approaches, and the June 6, 2012 Transit of Venus. Twice yearly “Sun Days” are conducted in association with the Denver Museum of Nature and Science.

The DAS is an active participant in the NASA/JPL Night Sky Network of astronomical observing clubs.

The Society’s Van Nattan-Hansen Scholarship Fund provides support to qualifying Denver-area students seeking degrees in astronomy, space-science and related programs.

The DAS is also active in the preservation of DU’s Historic Chamberlin Observatory, spearheading the drive for its listing in the National Register of Historic Places and promoting recent renovation activities by the University of Denver.

The DAS is a proud member of the Astronomical League, Mountain Astronomical Research Section (MARS), and all members of the society are members of the AL and entitled to its benefits.

Book Excerpt - How to See the 2017 Total Solar Eclipse

In May 2017, AgenaAstroProducts published its first e-book, How to See the 2017 Total Solar Eclipse. Written to help first-time eclipse watchers and casual stargazers prepare for upcoming eclipse in August, this book explains how to be in the right place at the right time-and with the right tools-to see this coast-to-coast total solar eclipse, the first in the U.S. in nearly a hundred years. The book is available on Amazon for less than four dollars.

Wondering what the book is all about? Here's an excerpt …

Chapter 2 - The Solar Eclipse of August 2017


Scientifically, the total solar eclipse of August 21, 2017 is not expected to be more important than any other total solar eclipse. But it will be the first coast-to-coast total solar eclipse across the continental United States in more than 99 years. There has been no total solar eclipse visible at all over the continental United States since February 26, 1979, when the path of the Moon's shadow traveled across Washington state, Idaho, Montana, and part of North Dakota before moving northeastward into the provinces of Manitoba, Ontario, and Quebec in Canada. The last 'coast-to-coast' eclipse in the U.S. happened on June 8, 1918 when the Moon's shadow passed rapidly over the country from Oregon to Florida.

Because of its location in a populous country, where more than 300 million people live within a day's drive of the path of totality, this will be perhaps the most watched astronomical event in history. The 'Great American Eclipse', as some call it, will give many sky watchers their best chance to see one of the most awesome spectacles in nature without the need to travel to a remote international location.

When and Where to See the August 2017 Eclipse

The path of totality of the eclipse-the narrow band where the total solar eclipse will be visible-passes through Oregon, Idaho, a tiny edge of southwestern Montana, Wyoming, Nebraska, extreme northeastern Kansas, a tiny piece of southwestern Iowa, Missouri, southern Illinois, Kentucky, Tennessee, northeastern Georgia, North Carolina, and South Carolina. The penumbra, where a partial solar eclipse will be visible, passes across the rest of the United States, all of Canada, Mexico, and Central America, and northern South America.

The total eclipse will also pass over cities and large towns including Salem, OR, Idaho Falls, ID, Casper, WY, North Platte and Lincoln, NE, Kansas City, MO (barely), southern St. Louis, MO, Nashville, TN, and Greenville and Charleston, SC. Along the center of the path of totality, the total solar eclipse will appear to last about two and a half minutes. The eclipse will last longest, about two minutes and forty seconds, near Carbondale, IL and Hopkinsville, KY.

The eclipse will occur on Monday, August 21, 2017 in the late morning and early-to-mid afternoon, local time, across the United States. It begins as the Moon's shadow falls on the north Pacific Ocean at 16:48:39 UT (Universal Time) or 09:48:39 Pacific Daylight Time (PDT) on the morning of August 21, 2017. The shadow makes landfall at 17:10:58 UT or 10:15:58 PDT on the Oregon coast, then speeds southeast over the continental United States for the next 93 minutes before moving over the coast of South Carolina into the Atlantic Ocean at 18:49:01 UT or 14:49:01 Eastern Daylight Time. The total eclipse continues into the Atlantic Ocean towards, but not reaching, Africa and ends at 20:01:35 UT, a little over three hours after it began.

To see the brief total solar eclipse along the path of totality, timing is essential: you must be on the path of totality at the right time. There are hundreds of towns and cities across the long and narrow path, too many to list in this book. This link from gives a table of the duration of the total eclipse in hundreds of towns across the U.S.:

And this video from shows a short but detailed video of the path of totality across the United States:

Figure 2-2, provided courtesy of, also shows the path of the eclipse across the U.S. This website has more detailed maps of the eclipse path across each state at this link.

Weather Prospects for the Eclipse

Astronomers can calculate the timing and position of a solar eclipse down to the second and the yard, but calculating the weather at any particular position is a much more challenging proposition. It's frustrating to travel for hundreds of miles (or more) to see a solar eclipse only to get clouded out. Even on a mostly sunny day, a patch of cumulus clouds can float across the Sun at just the wrong time. But predictions based on historical weather patterns during late August in each state suggest some locations offer a better chance of clear weather than others. Figure 2-3 shows the statistical chances of morning and afternoon clouds along the path of totality from coast to coast.

While the place of first landfall of the eclipse, on the coast of Oregon, is a geographically beautiful location, the chances of mid-morning fog are quite high. At the other end of the country, in North and South Carolina and Kentucky and Tennessee, the chances of afternoon clouds are also greater than 70%. It's also hurricane season on the east coast and it tends to be quite humid. It may be a beautiful day when the eclipse happens in these locations, but the odds are against it.

Most experienced eclipse watchers are planning on setting up in eastern Oregon in or near the little town of Madras. It sits at the intersection of four highways, allowing for last-minute movement to find the best sky if necessary. The cities of Salem and Portland have extensive lodging options and are just a few hours away. Salem itself sits in the path of totality, so it will be a busy place. Viewers in Portland will only see a partial eclipse. Madras is just east of the lovely stratovolcano Mt. Jefferson (Figure 2-4), so observers will see the peak of the mountain darken 17 seconds before the Moon's shadow rapidly descends on the town.

Some eclipse watchers and photographers looking for beautiful foregrounds in which to capture the eclipse will tryIdaho where weather prospects are good. In the eastern part of the state, Rexburg is a promising location. It's just north of Idaho Falls and offers good roads for mobility in case of last minute clouds. In the western part of the state, Highway 95 between Weiser (on the Snake River) and the Marin Creek Reservoir offers good odds for clear skies and totality durations of just over 2 minutes.Nearly smack on the centerline of the eclipse, Casper will be a popular place for eclipse watchers. Hardier souls and photographers may head to Grand Teton National Park in the western end of the state.

For observers near the center of the country,Nebraska is a good prospect to consider. The path of the eclipse runs from the northwestern to southeastern tips of the state from 11:46 a.m. MDT to 1:09 p.m. CDT (Nebraska encompasses two time zones). Highway I-80 from North Platte to Lincoln will serve as a main artery for eclipse chasers who can use the good road network here to move towards better weather. On the I-80 just south of Grand Island, the eclipse lasts 2 minutes and 30 seconds.

Moving east from Nebraska into Missouri, Illinois, and Kentucky, the chances for cloud cover increase, but many towns in these states-including Nashville-will organize events around the eclipse. Expect crowds in the larger cities and towns such as Nashville. Hotel rooms will be sold out months in advance. The Great Smoky Mountains National Park in North Carolina and Tennessee is a spectacular location to observe the eclipse, especially at high points such as Clingmans Dome where it may be possible to see the Moon's shadow moving across the surrounding landscape at more than a thousand miles an hour. Again, large crowds and the weather are the weak points here, and it may be difficult to maneuver out of the park at the last minute if the weather turns cloudy.

Wherever you go, if you can, stay mobile so you can evade cloud cover on the day of the eclipse. Locations with access to highways offer that option. Trying to observe the eclipse from rural areas or parks may make it harder to get on the move at the last minute. Since the eclipse occurs in summer, you may want to travel in an RV or pack a tent and sleeping bag in case you need to travel hundreds of miles from your home or hotel room and can't make it back after the eclipse.

Finding a Place or Event to See the 2017 Eclipse

Once you're in the path of totality and the weather looks promising, you need to find a place to sit or stand and enjoy the spectacle. There are tens of thousands of miles of open road from Oregon to South Carolina within the path of totality where you can pull over and see the event. Anyone can pull over off the road onto land that is governed by the U.S. Bureau of Land Management. There are also hundreds of towns each with areas or parking lots that can allow for great views. There will also be events organized in observing fields such as farms, parks, airports, and even stadiums. The website is a great resource to find a location with an organized event.

Useful Tools and Links

Eclipse Bulletin: Total Solar Eclipse of 2017 August 21. The eclipse expert Fred Espenak and his colleague Jay Anderson have created the highly detailed and authoritative Eclipse Bulletin, a 158-page guide packed with every conceivable detail about the August 2017 solar eclipse. The exact details about the path of the Moon's shadow can be found in a series of tables containing geographic coordinates, times, altitudes, and physical dimensions. A set of high resolution maps plot the total eclipse path across the USA. They show hundreds of cities and towns in the path, the location of major roads and highways, and the duration of totality with distance from the central line. Eclipse Bulletin: Total Solar Eclipse of 2017 August 21 is also available in color or black and white at the links below:
Color Edition:
Black and White Edition:

About the Author

Brian Ventrudo is a writer, scientist, and astronomy educator. He received his first telescope at the age of 5 and completed his first university course in astronomy at the age of 12, eventually receiving a master's degree in the subject. He also holds a Ph.D. in engineering physics from McMaster University. During a twenty-year scientific career, he developed laser systems to detect molecules found in interstellar space and planetary atmospheres, and leveraged his expertise to create laser technology for optical communications networks. Since 2008, Brian has taught astronomy to tens of thousands of stargazers through his websites and

About the Author

Manish Panjwani has been an active amateur astronomer since before Halley's Comet last flew by our neighborhood. A former wireless communications consulting engineer and management consultant to various Fortune 500 companies, Manish started Agena AstroProducts in 2003. Since then, Agena has become one of the leading online retailers of telescopes and astronomical accessories worldwide. Besides observing from his heavily light polluted backyard in Los Angeles, Manish enjoys conducting astronomy outreach programs in local schools. Manish also holds a Master's degree in Electrical Engineering from Virginia Tech and an MBA from the Kellogg School of Management at Northwestern University.

Solar Eclipse

Solar Eclipses: An Observer's Guide (Infographic)
How Solar Eclipses Work: When the moon covers up the sun, skywatchers delight in the opportunity to see a rare spectacle.

Solar Eclipses Were not Always Enjoyed
Eclipses have been watched for centuries, but it was only recently that we understood what really occurs. Eclipses have always been fascinating to watch, but they weren't always welcome. For many years, civilizations around the world feared these rare occasions.

Solar eclipse 2021: Prepare for a "ring of fire" on June 10
In a few weeks, the Moon will almost entirely blot out the Sun in a stunning annular eclipse. So, grab your eclipse glasses and get ready.

Activity for a Sunny Day
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of March 20, 2015, was the first occurrence of an eclipse estimated to potentially have a significant impact on the power system, with the electricity sector taking measures to mitigate any impact.

Information at the Solar Data Analysis Center." .
U. S. Naval Observatory Astronomical Applications Department. "Upcoming Eclipses of the Sun and Moon." .

timings from any position on Earth? (Intermediate) .

is an event that occurs when the Moon passes between the Earth and the Sun, partially or totally blocking the sunlight.

s are the result of a fortunate coincidence. Because the Sun and the Moon are almost exactly the same angular size as we see them from Earth, during a total eclipse the Moon covers the bright disk of the Sun, but little or none of the surrounding space.

s are caused by the passage of Phobos between Mars and the Sun.

s are seen underneath the penumbra.

will stretch from Canada to Siberia via the North Pole. See the map below to find out how much of the Sun's surface will be covred by the Moon and at what time it will occur depending on your location.

so long as is total at some place on the earth during the celestial spectacle.

Please be sure to read our Solar Viewing Safety page.
The ecliptic is the a virtual plane that splits the Sun in half. Along this plane orbits the 9 planets, their moons and the asteroids.

s occur when the Sun, the Moon and the Earth are exactly lined up, so that the Moon's shadow reaches the surface of the Earth.

can occur only when the moon is in its new phase. At this time the moon is between the sun and the earth and cannot be seen until it moves across the sun's disk.

This alignment of the Sun, Moon and Earth also resulted in a partial

on September 13, visible only from parts of Africa and Antarctica.

occurs when the Moon passes between Earth and the Sun, thereby totally or partially obscuring the image of the Sun for a viewer on Earth.

s come in three types total, partial, and annular. The appearance of each of these depends on the density of the lunar shadow that passes over your location.

Birds nest at midday, chirp night
songs in midday twilight-night
without sunset, the sun noon
high, bruised black by the moon.
- Deborah Trustman, "The Eclipse", 1975 .

can only happen when the Moon is in the new moon position, and can only be observed for a few moment by observers in a small strip of Earth's surface called the path of totality.

Celestial event during which the new Moon passes directly between the Earth and Sun, temporarily blocking the Sun's light.
solar interior The region of the Sun between the solar core and the photosphere.

-- the passage of the new Moon directly between the Sun and the Earth when the Moon's shadow is cast upon the Earth. The Sun appears in the sky either partially or totally covered by the Moon.

occurs when the Moon passes between the Earth and the Sun.
solar flares .

A shadow which falls on an area of Earth when the Moon moves between the Sun and Earth.
A magnetic storm on the Sun's surface which shows up as a sudden increase in brightness.

the moon blocks out the light from the solar disk, allowing us to see the solar corona more clearly. Coronagraphs essentially create artificial eclipses so that the corona can be studied continually.
Solar Flare .

An eclipse occurs when one celestial body, such as the moon or a planet, moves into the shadow of another celestial body.
Read More .

" Term that describes when the Sun is obscured by the Moon from the perspective of Earth.

as total.
South Celestial Pole
The point in the sky directly above Earth's south pole.

occurs when the Moon is farther away and is not able to completely block the light.

: A phenomenon that occurs when the Earth passes into the shadow of the Moon.
Solar Flare: A brilliant outbreak in the Sun's outer atmosphere, usually associated with active groups of sunspots.

- When the moon passes between the earth and the sun.
Solar filter - A safety precaution, a filter used to block almost all the suns light when being viewed.
Solar irradiance - Radiant energy given by the sun over all wavelengths that falls each moment on one square meter of earth's atmosphere.

, the Sun dims as it is covered by the Moon. During a total eclipse, the entire Sun is covered for a few minutes and the sky darkens and the temperature drops.

- Lunar Eclipses - primary page for lunar eclipse predictions .

: Anyone on Earth who lives in an area where the Moon's umbra passes will see the entire Sun obscured by the Moon. For example: Astronomy Picture of the Day: 2002 December 6.

Taken at 3:01pm 21/06/01 Chinyingi, Zambia with an Elite 200, Meade 2045D 1 sec.

This is when the Sun goes dark. It occurs because the earth's shadow appears to "eat away" the glow of the sun. Note: it is very important to wear solar glasses when observing the Sun, otherwise blindness may occur.

s can only occur within a few days of the New Moon, but they do not happen at every New Moon. This is due to the 5.1 degree tilt of the Moon's orbit around the Earth compared to the Earth's orbit around the Sun.

. Image credit: Fred Espenak, NASA
Every now and then, the Moon destroys the Sun. Okay, not destroys, covers. Well, not really covers, but from here on Earth, sitting inside the shadow of the Moon, that's what it sure looks like.

visible in the United States occurred in 1979 and the next one will not take place until 2024.

Solar Rain Just like Earth, it sometimes rains on the Sun. But this rain is not made of water, it is made of electrically charged, superheated gas, called plasma.

4.7 Eclipses of the Sun and Moon
solar flare15.3 Solar Activity above the Photosphere, 15.4 Space Weather, 16.4 The Solar Interior: Observations
solar interior16.3 The Solar Interior: Theory, 16.4 The Solar Interior: Observations .

Partial or total blocking of the Sun's light by an astronomical body (in most usages, by the Moon).
solar flare .

(left) the Sun's photosphere is completely obscured by the Moon's disk in the area covered by the cone of shadow. In an annular eclipse (right) the Moon is slightly farther away and so the cone of shadow does not reach the Earth.

occurs during a new moon, when the moon is directly between Earth and the sun, as per the illustration on the left, which is not to scale. When this happens, the moon blocks the sun's light from reaching Earth in two main ways.

(see Eclipse, Solar) in which the Solar disk is never completely covered but is seen as an annulus or ring at maximum eclipse. An annular eclipse occurs when the apparent disk of the Moon is smaller than that of the Sun. [S92]
Eclipse, Lunar .

occurs during a new Moon, when the Moon is between the Sun and Earth. Since they are the same apparent size in the sky, the moon can either partially block the Sun (annular eclipse) or fully block it (total eclipse).

at ESO HQ - 11.08.1999
The Leonids - 11.1998
Mars Pathfinder - 1997
Comet Hyakutake - 1997
SL-9 and Jupiter - 1994
Comet Hale Bopp - 1994 .

in 1973 showing the corona (courtesy of Fred Espenak).
The corona is known to be very hot because it has ions with many electrons removed from the atoms. At high enough temperatures the atoms collide with each other with such energy to eject electrons. This process is called ionization.

Date: Sunday 3 November 2013
Location: North Atlantic and Africa
More information: .

will be visible from a narrow path across the western United States on the afternoon of May 20. This map shows the path, with the peak of the eclipse in local time (p.m.). Viewers outside this path will see a partial eclipse.

s are rare, not every month. Try a phase of 0.5001 for a cool view of an eclipse (be sure to use Earth View).
Source: .

Prob. 3.1: In Lecture 3, we gave the equation for plate scale, and an example of how to calculate the linear size of an object at the focal plane of a telescope.

International Spacecraft Reveals Detailed Processes on the Sun
NASA released on Wednesday never-before-seen images that show the sun's magnetic field is much more turbulent and dynamic than previously known. The international spacecraft Hinode, formerly known as Solar B, took the images.

. particle 1. An elementary subatomic particle such as proton, electron, neutron, etc. 2. A very small piece of matter. 3.

(see eclipse, solar), measured along the common diameter.

- The most dramatic example of a transit, when the moon passes between the Sun and Earth. The sunlight we receive dims dramatically because the moon blocks our view of the Sun.
Solar System - A star (sometimes more than one star) and all the objects that orbit it. Also known as star system.

If the Moon and Sun are at the same node, the Moon passes in front of the Sun and a

results, lasting only a few minutes in duration. If the two are at opposite nodes, then the Moon passes through the shadow of the Earth and a longer duration lunar eclipse occurs.

s will occur once each Plutonian day, with a maximum duration of 90 minutes.[29][30]

in which the Moon is too far from the Earth to block the entire Sun from view and a thin ring of sunlight appears around the Moon
Antapex - The direction in the sky away from which the Sun is moving. Because of the Sun's motion, nearby stars appear to converge toward the antapex .

The chromosphere is the source of the strongest lines in the solar spectrum, including the Balmer alpha line of hydrogen and the H and K lines of calcium, and is the source of the red (chromium) color often seen around the rim of the moon at total

It is visible to the naked eye during a

. Coronagraph Telescope for observing the corona. Often contains an occulting disk which covers the disk of the Sun so that the corona may be more easily observed. CDS Coronal Diagnostic Spectrometer.
An ultraviolet spectrometer aboard SOHO.

CORONA: The high-temperature outermost atmosphere of the sun, visible from Earth only during a total

CORONAGRAPH: A special telescope which blocks light from the disk of the Sun in order to study the faint solar atmosphere.

visible in one place won't necessarily be visible elsewhere.) To enter a new lat/lon, use the Location dialog in the Settings menu.

It is visible to the naked eye during a

Density The amount of mass or number of particles per unit volume. In cgs units mass density has units of gm cm-3. Number density has units cm-3 (particles per cubic centimeter).

, from Universal Geography, 1711. Geography and Maps Division One of the other key pieces of evidence for a round Earth was the fact that at a distance one can see the top of a ship before seeing the rest of it.

Annular eclipse - a type of

in which a ring (annulus) of sunlight remains visible.
Asteroid - a "minor planet" ,a chunk of rock smaller than planet-size but larger than a meteoroid, in orbit around a star.

if the alignment is slighly imperfect then the Moon covers only part of the Sun's disk and the event is called a partial eclipse. When it lines up perfectly the entire solar disk is blocked and it is called a total eclipse of the Sun.

You were probably told in elementary school "Don't ever look at a

- you'll go blind!" or something like that. That's not entirely true, though you have a pretty good opportunity to really screw up your eyes if you are really stupid.

. It was one of the biggest internet events in recent history and the biggest online event NASA has ever measured. There were more than 50 million views of the live broadcast on NASA.

happens when the moon moves between the earth and the sun. The sky slowly gets dark as the moon moves in front of the sun. A total eclipse happens when the moon and sun are in a perfect line. These are very rare. Most people only see one in their lifetime.

You all have seen them, usually advertised before

s. They are made from special film/foil that is acting as a filter. You could also smoke a glass and use it, but I do not recommend it. Another way of homemade glasses is using a photographing film or a wielder's mask/glass.

There was one more flurry after the total

at July 29 1878, where two observers claimed to have seen in the vicinity of the Sun small illuminated disks which could only be small planets inside Mercury's orbit: J.

International fame came to Einstein in November 1919, when the Royal Society of London announced that its scientific expedition to Prmncipe Island, in the Gulf of Guinea, had photographed the

on May 29 of that year and completed calculations that verified the predictions made in Einstein's general theory .

Finally the outermost layer of the Sun is the corona, a region of diffuse glowing gas which can only be seen from Earth when the much brighter glare from the Sun is blocked by a

I will tell you what I saw during two complete

s that I've witnessed! We'll conclude this lesson by talking you through the path of an eclipse.
Multiple Star Systems (Check the study guide for this lesson) .

What Is the Difference Between the Lunar Calendar & the Solar Calendar?

[10] Section #8b, about using a total

to estimate the distance of the Moon, includes a map of the eclipse of August 11, 1999. The path of totality across the Black Sea is shown, as are samples of the region of totality at selected times. You will notice that region is nearly circular.

The outer part of the Sun's atmosphere. The corona is visible from Earth during a total

Cosmic Ray
Atomic nuclei (mostly protons) that are observed to strike the Earth's atmosphere with extremely high amounts of energy.

Just as totality begins during a

(from "Kontinuum") Of the white light corona (that is, the corona seen by the eye at a total

), that portion which is caused by sunlight scattered by protons and free electrons in the hot outer atmosphere of the Sun. The K corona extends out to about 700,000 km from the photosphere.

Yohkoh suffered a spacecraft failure in December 2001 that has put an end to this mission. During the

of December 14th the spacecraft lost pointing and the batteries discharged. The spacecraft operators were unable to command the satellite to point toward the sun.
Yohkoh Mission Web Links .

Most widely used in astronomy in connection with the fraction of a disc of the Moon or a planet which is illuminated by the Sun. Phase is also used in connection with lunar and

A transit of Venus across the face of the Sun isn't a

. The Sun is neither blotted out nor dimmed. In fact, Venus is too small. The disk of the planet covers only 0.1 percent of the Sun.

Umbra: The darkest part of the shadow cast by an astronomical object. The umbra of a

is the region wherein the eclipse is total. The penumbra surrounds the umbra, and is the region which sees a partial eclipse.
Zenith: The point in the sky directly overhead.

in 1919 measured this larger value for the deflection. Currently the deflection of "light" is best measured using radio astronomy, since radio waves can be measured during the day without waiting for an eclipse of the Sun. Lebach et al. (1995, PRL, 75, 1439) find a deflection of 0.

A lunar eclipse: August 16/17, 1989 over North America
A partial

: March 7, 1989, over Alaska
A Globe-skimming eclipse: October 3, 1986, over Iceland.
Mankind's Comet .

Discover the colour techniques he uses to take amazing photographs like this

. And learn how to take beautiful star trail photos with a digital camera.
Discover new galaxies .

Eclipse: An event predicted by astronomy, that occurs when the shadow of a planet or moon falls upon a second body. A

occurs when the Moon's shadow falls upon Earth, which we see as the Moon blocking the Sun. When Earth's shadow falls upon the Moon, it causes a lunar eclipse.

[Pictured: Moon traversing the face of the sun during a

solar: an eclipse of the sun caused by the moon passing between Earth and the sun. lunar: an eclipse of the moon caused by the Earth passing between the sun and moon. annular: a

in which the moon does not fully cover the sun's disk, allowing observers to see a thin ring of sunlight.

Eclipse An alignment of two bodies with the observer such that either the nearer body prevents the light from the further body from reaching the observer (strictly speaking, these are occultations), e.g.

or eclipsing binary stars, or when one body passes through the shadow of another, e.g.

A type of telescope with which the corona can be seen at times other than that of a total

Time for an International Standard

A total solar eclipse is probably the most spectacular astronomical event that most people will experience in their lives. There is a great deal of interest in watching eclipses, and in the days and weeks before an eclipse occurs, there are often news stories and announcements in the media, providing information on what will happen, and how to watch the eclipse safely.

Unfortunately, despite the best intentions, the news media often provide inaccurate information on safe observing techniques. This is especially true when the subject of protective filters for direct observation of the sun is raised. Over the past five years, I have been asked to comment on the safety of using devices such as floppy disk media, multiple layers of space blanket (a very thin type of aluminized polyester), compact disks (CDs) and metal coated polyester wrappers as solar filters. There are now several manufacturers of solar filters intended for both visual and photographic use who were not operating in 1981 when I first published solar filter data in Sky and Telescope (August, 1981).

An invitation to participate in a NATO-sponsored meeting on solar eclipse astronomy in June, 1996, prompted me to make spectrophotometric measurements of a variety of solar filter materials and assess whether these filters provide adequate protection for the eyes.

Retinal Burns

Solar radiation reaching the surface of the earth ranges from ultraviolet (UV) radiation at wavelengths longer than 290 nm to radio waves in the metre range. It is widely accepted that environmental exposure to high levels of solar UV radiation contributes to the accelerated ageing of the outer layers of the eye and skin, and the development of cataracts. However, observing the sun with inadequate or no eye protection results in "eclipse blindness" or retinal burns because the eye transmits most of the optical radiation between 380 nm and 1400 nm to the light-sensitive retina.

Exposure of the retina to high irradiance levels of visible light triggers a series of complex chemical reactions within the light-sensitive rod and cone cells. The resulting photoproducts damage the cells, impairing their ability to respond to light, and in extreme cases can destroy them. Depending on the severity of the damage, an affected observer experiences either a temporary or permanent loss of visual function. This photochemical retinal injury mainly occurs when the retina is exposed to blue and green light. Longer wavelengths of visible light and near-IR radiation are absorbed by the dark pigment epithelium below the retina, and converted into heat which can literally cook the exposed tissue. This thermal damage also occurs during extended exposure to blue and green light. Photocoagulation destroys the rods and cones, leaving a permanently blind area in the retina.

Each wavelength of optical radiation has an associated threshold retinal exposure level that must be exceeded in order for retinal damage to be observed - shorter wavelengths are more effective in that less energy is needed. The danger to vision of inadequately protected viewing of the sun is significant because light-induced retinal injuries occur without any feeling of pain (there are no pain receptors in the retina), and the visual effects do not occur for at least several hours after the damage is done.

Because the threshold exposure levels for photic damage to the retina at each wavelength of the optical spectrum are well known, it is fairly simple to calculate the maximum permissible filter transmittance that will provide adequate retinal protection from sunlight. The ratio between the threshold retinal irradiance for light damage to the solar spectral irradiance at each wavelength provides a starting point for this. The worst case scenario assumes that the sun is at the zenith in a clear sky (air mass of 1). The maximum permissible transmittance level of the filter at a given wavelength can be arbitrarily set at between one per cent and 0.1% of this ratio to provide a "safety" factor. When this is done for the waveband between 380 and 1400 nm, we find that a filter with a luminous transmittance of 0.0032% in the visible spectrum corresponding to a shade number of 12 provides "adequate" retinal protection during solar viewing. However, this does not take into account visual comfort for comfortable viewing of the sun, a filter with a luminous transmittance of 0.0003% (shade number 14) is often preferable.

Measuring Filter Transmittance

Filter materials that were tested are shown in Table 1. Solar filter materials were randomly selected from the manufacturers' stock. The photographic film samples were purchased from a local retailer, then exposed to full sunlight and developed to maximum density according to the manufacturers' instructions. The smoked glass filter was produced by depositing soot from a candle flame onto a glass microscope slide. The other materials were obtained by random selection from retailers' stock.

Transmittance measurements were made with a Cary 5 spectrophotometer at 5 nm intervals over the waveband 200 to 2500 nm, and the data were stored as Lotus spreadsheet files. A rear-beam attenuator accessory was used to reduce the noise level, but there was still a significant level of signal fluctuation in the infrared (IR) and ultraviolet (UV) regions of the spectrum. This is a common problem when measuring transmittance of high-density filter materials.

Microsoft Excel workbooks developed in the Ophthalmic Standards Laboratory at the School of Optometry, University of Waterloo, were used to calculate luminous transmittance, shade number, and mean transmittance in two UV wavebands (200 to 315 nm and 315 to 380 nm) and the near-IR (780 to 1400 nm). These calculations are specified in the American National Standard Practice for Occupational and Educational Eye and Face Protection (ANSI Z87.1-1989). The data are shown in Table 2. The spectral transmittance curves for these solar filter materials are shown in the accompanying figures.

Relative Safety of Solar Filter Materials

Not surprisingly, there was a wide range in the attenuation of visible light by these filter materials. Even among the "safe" filters, there was considerable variation in transmission levels. For example, the differences in processing methods and chemistry resulted in considerable variation in optical density of the silver-bearing black-and-white film emulsions. The double-layer filters had shade numbers between 11 and 16.

I have recently also found a wide range of optical density between individual audio and data compact disks (CD and CD-ROM) because of variations in manufacturing processes. Some compact disks have aluminum films which are so thin that they appear semi-transparent at normal room illumination levels. These CDs are unsuitable for use as solar filters. Higher quality CDs are suitable for use if the aluminum coating is dense enough that the glowing filament of an incandescent light bulb is just barely visible through it.

Floppy disk media have a marginally safe infrared transmission, and produce poor quality images of the solar disk. The magnetic media scatters visible light to the extent that one sees a dull red disk surrounded by a broad halo of red light. I would not recommend using this material for a solar filter.

The most consistent performance was found with the polyester and glass filters. I would avoid aluminized polyester which is used in wrappers for food products and collector cards because of the inconsistent optical quality, but even my sample of Poptarts wrapper performed surprisingly well in terms of protection from optical radiation. (It rated as marginally safe.) However, most of the filter materials specifically designed for eye protection easily met all of the transmittance criteria for safe filters.

Unsafe filters include any image-bearing photographic emulsion, chromogenic (non-silver-bearing) black-and-white film, black processed color film, photographic neutral density filters and polarizing filters. Although these materials have very low luminous transmittance levels, they transmit an unacceptably high level of near-infrared radiation. The black color film is a good example, having a shade number of 15 for visible light, but transmitting almost 50% of the infrared radiation!

Infrared transmittance levels shown in Table 2 should be regarded as the upper limit of transmittance in the waveband 780 to 1400 nm. The signal-to-noise ratio for low-level measurements in this waveband is extremely low, and thus these data are less reliable than those in the shorter wavebands. Note that even some glass filters with very good safety performance histories such as the Questar and Thousand Oaks glass filters showed infrared transmission levels up to 0.4%.

Smoked glass had very good performance in terms of transmission of visible light and infrared radiation. However, it is a dangerous filter material for two reasons. First, it is very difficult to produce a heavy uniform coating of soot on glass. Second, the coating is very fragile. It is very easy to destroy the filter by handling it. Much of the soot on my sample came off because of contact with its protective wrapping. It also made quite a mess.

Moving toward an International Standard?

As manufacturers of protective solar filters try to expand their markets beyond North America, they inevitably encounter skepticism from the medical community and government, as well as regulatory obstacles. For example, a company began efforts to distribute polyester solar filters in the United Kingdom in advance of the partial solar eclipse of 12 October 1996. However, as a member of the European economic union, the United Kingdom required that solar eclipse "glasses" incorporating polyester filter materials bear the "CE" mark. This required testing to certify the eclipse glasses as meeting the Basic Health and Safety Requirements (Annex II) of the European Community Directive 89/686/EEC on Personal Protective Equipment. I prepared a technical specification for "Protective Filters for Direct Visual Observation of the Sun" which specifies materials, filter transmittance, filter mounting and labelling requirements for both filters intended for unaided visual observations of the sun and direct solar observations with optical aids. The complete technical specification was reviewed and accepted by a British certifying agency as compliant with the EC directive.

Filters intended for unaided visual observation of the sun


Filters may be made of tempered glass (minimum thickness 3 mm), polycarbonate, polyester film, or any other material which provides a suitable substrate for an absorptive filter, or a vacuum-deposited metallic reflective coating, which meets the requirements for filter transmittance.

Filter Transmittance

The luminous transmittance of the filter, when determined as described in clause 6 of EN167, shall not exceed 0.0032%. Filter transmittance in the waveband 280 to 380 nm (ultraviolet radiation) shall not exceed 0.003% at any wavelength. Transmittance in the near infrared waveband (780 to 1400 nm) shall not exceed 0.027% at any wavelength. Filters with luminous transmittance (in the waveband 380 to 780 nm) equivalent to scale number 12 to 16 as specified in Table 1 of EN169:1992 are considered suitable for direct observation of the sun. It should be noted that many observers will find the solar image uncomfortably bright when filters with scale numbers of 12 or 13 are used.

Filter Mounting

Filters may be made with or without a mounting. A mounting shall hold the filter securely so that it cannot be displaced by normal handling or by gusts of wind. Mountings may be handheld, or shaped in the form of spectacles to be worn on the face in front of any corrective (spectacle or contact) lenses worn by the user. The filter or filter and mounting assembly shall be of a size sufficient to cover both eyes of the user simultaneously, and in no case shall have overall dimensions less than 115 mm in width and 35 mm in depth in the plane parallel to the facial plane. Spectacle shaped mountings may have a triangular cut-away area to accommodate the crest of the nose, not to exceed 15 mm in apical height and 35 mm width at the base. The filter and mounting shall be free from roughness, sharp edges, projections or other defects which could cause discomfort or injury during use. No part of the filter or mounting which is in contact with the wearer shall be made of materials which are known to cause any skin irritation.


The filter and/or its packaging shall show the following information: a) name and address of manufacturer and/or distributor of the product b) instructions for use in looking at the sun or a solar eclipse c) warnings that filters that are damaged or separated from their mountings should be discarded and d) warnings against the use of the filter with optical devices such as binoculars, telescopes or cameras e) advice on storage, cleaning and maintenance, as appropriate. f) the relevant protection-factor number of the filter. g) the obsolescence deadline or period of obsolescence, as appropriate.

When the stringent requirements of the European Community Directive are considered, this specification may be suitable as an international performance standard for all solar filters. Adoption of such a "standard" would give astronomers who are asked to advise government authorities on safe solar viewing techniques a reference which addresses the public safety concerns over these devices.

Filters for visual and photographic use

Acceptable filters for unaided visual observations include: aluminized polyester specifically designed for solar viewing, shade 12 and 14 welding filters, black polymer filters (Thousand Oaks Solar Shield 2000 and Rainbow Symphony Polymer), and two layers of fully exposed and developed silver-bearing black and white film negative. For photographic and visual use, particularly with binoculars or telescopes, acceptable filters include: aluminized polyester specifically designed for the purpose, and Questar and Thousand Oaks T1 and T2 glass filters. The Thousand Oaks T3 filter should be used with extreme care for photographic use only.

Not recommended are: metal-coated polyester that is not specifically intended for solar observation, smoked glass, floppy disk media, black colour transparency (slide) film, floppy disk media, and compact disks (because of the inconsistent quality of the metal coating).

Additional Reading

My data and comments on safe solar filters will appear in the NASA solar eclipse publications by Fred Espenak and Jay Anderson, beginning with NASA RP1398: Total Solar Eclipse of 1999 August 11.

Lunar Eclipse

“A lunar eclipse occurs when the Moon moves through the Earth’s shadow, thereby blocking sunlight from falling on the Moon” (Haynes & Churchman, 2014, par. 3). The lunar eclipses are the more common phenomena than the solar eclipses, and they usually last for a longer time – about one hour. It happens because the shadow cast by the Earth is more extent than the Moon.

“When a total lunar eclipse is preceded and followed by lunar eclipses that are not total ones, then it is known as an isolated total lunar eclipse” (West, 2012, p. 277). The isolated total lunar eclipses usually occur in groups of two or three. It means that three successive total lunar eclipses can occur and then be separated from another group of the total lunar eclipses by the series of the partial eclipses. The group consisted of the four total lunar eclipses is a rare phenomenon. These eclipses are called tetrads (West, 2012, p. 277).

In the time of the total lunar eclipse, the Moon is painted red. Although one can expect that the shadow would look dark, as normally the shadows do, when the Earth’s shadow covers the Moon completely, it turns red. The reason for it is in the planet’s atmosphere. When the sunlight passes through the Earth’s atmosphere, it filters out, and the human eyes perceive it in the red colors. In the same way, the sunlight is filtered by the atmosphere in the daylight when the sky seems to be blue.

The eclipse is best seen when the sky is clear, and there is no atmospheric haze. Similarly to the solar eclipse, the possibility of observing the lunar eclipse is dependent on the location and longitude. However, “observing a lunar eclipse, unlike a solar eclipse, is safe to do and requires no special observation equipment” (Riddle, 2007, p. 77). But the when observed through a small telescoped, the eclipse is seen in more details.

How to stay safe during solar eclipse in Fargo-Moorhead

If you're planning on watching the solar eclipse in two weeks, beware.

You'll need the right safety gear to watch this spectacle in the sky.

"Astronomers are calling it the great american eclipse," said Juan Cabanela, MSUM astronomy professor.

In two weeks the moon will pass over the sun, but this isn't just any eclipse.

It's the the first total solar eclipse to hit North America since 1979.

Even though Fargo-Moorhead will only be treated to a "partial eclipse," astronomers say it's still a sight to see.

"A partial is still really neat, and you still have the moon and sun lining up, and you don't have that very often," said Sara Schultz, MSUM planetarium director.

But before you can see the phenomenon, you need to protect your eyes.

"There's so much hype over it that a few reputable people are selling plastic glasses as eclipse lens," said Cabanela.

Astronomers say fake solar glasses look exactly like reputable brands, but could give you permanent eye damage.

To help you out, the American Astronomical Society has released a list of approved supplies and vendors.

If you put regulation glasses on, you can stare directly into the sun without damaging your eyes.

It's important to have solar glasses. Using normal sunglasses or even a welder's mask won't work.

But astronomers hope that won't deter people from experiencing the eclipse.

"I'm really excited to inspire the next generation too, and kind of get that spark early so that they realize there's really cool stuff if you're paying attention," said Schultz.

So, if you are watching the skies, remember to put on your glasses and enjoy the view.

MSUM will hold a watch party on the west side of campus in the parking lot. They'll have telescopes and glasses to see the event.

You can also go to the college's bookstore to buy the glasses beforehand for only a dollar.

Watch the video: How to SAFELY view an Eclipse and Find Sunspots (August 2022).