2017 Solar Eclipse on August 21

Overview

Do NOT use a telescope or your naked eye to observe the partial eclipse in Central Illinois.

On August 21, 2017 the Moon will pass between the Earth and the Sun, casting a shadow on the Earth that will travel west to east across the continental US.  Only a small strip of the US will get to see a total eclipse (which completely covers the Sun).  The total eclipse will be visible in southern Illinois (near Carbondale).  That is a short drive for those of us in Central Illinois and it is worth it to get to a place where you will see the total eclipse. Keep in mind if its cloudy it is cloudy.  There are no do-overs for clouds.  Also consider planning in advance because many other people will be trying to do the same thing on the same day.

For information about the path of totality see the web page at NASA.

If you want to stay home here in Central Illinois, you won’t get to see a total eclipse but you will see a partial eclipse.  People in Springfield, Jacksonville, and Decatur will get to see more than 94% of the Sun covered.  This page is to help people staying in Central Illinois to get the most out of the partial eclipse.

Do NOT use a telescope or your naked eye to observe the partial eclipse in Central Illinois.

Is the UIS Observatory Doing Anything for the August 21 Eclipse?

The UIS Observatory will not be having an event for the August 21 eclipse.

The partial eclipse doesn’t even begin to compare with a total eclipse.   This event is much more spectacular if you travel not that far to see the total. I am heading to a good weather spot in the zone of totality on August 21 to see a total eclipse.

We will be hosting an event to watch the Perseid Meteors on August 12.

Here is information about Friday Night Star Parties in September & October.

Partial Eclipse Observing

Warning!

Staring at the Sun can harm your eyes.  This is true even when the Sun is mostly covered.  The Sun is really bright so even if 99% is covered it can be as bright as staring into a 1000W halogen work lamp at arm’s length.  (Below we explain how that is calculated).

Do NOT use a telescope or your naked eye to observe the partial eclipse in Central Illinois.

Safe Viewing

Do NOT use a telescope or your naked eye to observe the partial eclipse in Central Illinois.

Video

Special Solar Glasses

Several companies and non-profits are selling solar glasses to view the 2017 eclipse.  It is safe to use properly constructed solar glasses to do that.  Basically a well constructed layering of polarizing film or a #14 welder’s glass blocks enough light to make it safe.  Generally speaking, the glasses are safe it’s hard to see anything but the Sun through them.  Keep in mind that you are trusting  your eyes and safety to whoever made the glasses.  So use good judgement and buy only from reputable sources.

Normal sunglasses do NOT provide enough protection.  If the Sun feels like it is really bright through any glasses, stop looking at the Sun through them.  If your eyes want to blink and stay shut, your reflexes are telling you that it isn’t safe.

Here is a list of vendors of solar viewing glasses and solar filters for telescopes meeting the appropriate safety standard (page by the American Astronomical Society).

Pin-Hole Camera

The easiest and guaranteed safe way to observe a partial solar eclipse is with a camera obscura, otherwise known as a pin-hole camera.

Here is a NASA website that teaches you how to build a pin-hole camera.

I suggest that corrugated cardboard is good for the structural pieces.  But a piece of thin cardboard (i.e. back of a legal pad, cereal box, food packaging) is best for putting a small round hole in.  It can be difficult to get the hole small and uniform through a piece of foil or thicker cardboard.

I like to make my pin-hole camera with an old cardboard box because then you can put it over your head and watch shaded from the Sun.   I’d supervise any scissors or pin use to make it, but once it is made this is so safe that I’ve let my grade-school aged daughter do it herself unattended.  Also, use common sense about running around with a box over your head.

Do NOT use a telescope or your naked eye to observe the partial eclipse in Central Illinois.

Timing

Here is an interactive map to get start, max coverage, and end times for the eclipse anywhere in the continental US (note that Central Daylight Time = UTC – 5 hours).

On August 21 in Central Illinois the Moon starts to cover the Sun at about 11:50 am CDT.  The Sun will gradually become more covered.  The maximum amount of coverage will happen around 1:20 pm CDT.  Then the Moon will uncover the Sun with the eclipse ending at about 2:45 pm CDT.

Map showing maximum eclipse coverage in Central Illinois for partial solar eclipse on 2017 August 21
Map showing maximum eclipse coverage in Central Illinois for partial solar eclipse on 2017 August 21

The map at right shows the maximum coverage of the Sun across Central Illinois.  In Springfield about 96% will be covered.  In Jacksonville it will be 97% and in Decatur it will be 95%.

Remember ANY percent of the Sun uncovered is dangerous to look at through a telescope or your eye!

Do NOT use a telescope or your naked eye to observe the partial eclipse in Central Illinois.

How Bright Will The Sun Be At Max Coverage?

The Sun is very bright.  Putting it in terms used to describe light bulbs, the Sun is 9.3 million lumens.  That is simply outrageous compared to any lightbulb you can buy.

You probably noticed at night that a street lamp you are standing under is brighter than one a block away.  That is because even though the street lamps are the same light bulb with the same lumens rating, the further you are from it the less of the light makes it to you eye.  Same with the Sun.  It is brighter on Mercury (closer to the Sun) than it is on Earth.  It is fainter on Mars (further from the Sun) than it is on Earth.

So at a distance of 150 million kilometers, the uncovered Sun drops about 1050 Watts per square meter on the surface of the Earth.  That is 98,000 lux.

If only 4% of the Sun is uncovered (like it will be at max partial eclipse of 96% at about 1:20 pm on August 21 in Springfield) then it is dropping 3900 lux on your eye.

For comparison, a 1000 Watt halogen bulb shines with about 16,000 lumen.  Held at arm’s length (about 1 meter away) it would have a brightness of 1300 lux.  OR held 0.61m ( 2 feet) from your face it would have a brightness of just under 3500 lux.

Don’t try that at home.  Staring into a 1000 Watt halogen bulb two feet from your face is not a healthy activity.  It will cause eye damage.  Same for only 4% of the Sun.  Even covered 96% the Sun is still so bright that it will hurt you to look at it.

Please be safe on August 21 and use good solar glasses or a pin-hole camera so that you can painlessly enjoy the partial eclipse in Central Illinois.

Do NOT use a telescope or your naked eye to observe the partial eclipse in Central Illinois.