Wednesday, October 12, 2016

The Big Eclipse - Part 4: What to Expect

Composite of March 2016 eclipse by Justin Ng,
This post will start to cover what you can expect on eclipse day itself.  It's going to be a very exciting day, and parts of it will fly by so fast you may miss things if you don't know to look for them.  I'll cover the partial phases in this post, and then the moments right before totality and totality itself in the next one.

First, it helps to remember and visualize what's actually happening here.  The moon orbits the earth in approximately the same plane as the earth and sun.  That means that every 29 and a half days the moon gets between the earth and sun.  However, the moon's orbital plane isn't exactly the same as the earth and sun so usually rather than getting right in front of the sun, it is slightly above or below the sun so we don't see a solar eclipse every month, we just get a new moon.  However, every once in a while, new moon occurs at those points in its orbit that do fall exactly between the sun and the earth, and we get a solar eclipse.  The next very cool fact is that even through the sun is much, much larger than the moon, it is also much further away.  In fact, the size of the moon and size of the sun and their distances from the earth just happen to work out so that the moon appears to be exactly the same size as the sun when viewed from earth.  Actually, depending on where the moon is in its orbit, it may appear slightly larger or slightly smaller, hence annular eclipses vs. total eclipses.  As soon as you get your safe solar filter, go outside and look at the sun through it.  It is the same size as the full moon!  Cool, huh?

First Contact
So, in short, the moon is slowly moving across the sky in its orbit and is about to cross in front of the sun.  You won't be able to see the moon itself in the sky because it's illuminated side is pointed away from us, toward the sun.  But you will be able to see the moon start to pass in front of the sun.  The moment that the edge of the moon is first detectable in front of the sun is called "first contact" and is the beginning of the eclipse.

For the next hour or so, you will see the moon continue to move in front of the sun, blocking out more and more of it.  There are several things to look for during this time, especially as totality approaches.  First, it's going to get darker, but not as much as you might think.  The sun is very bright, and even when some of it is still showing, there will be plenty of light.
It's really important to continue to use your safe solar filter during the entire partial phase of the eclipse.  But now is also the time to look for as many "pinholes" as you can find around you and use them to project images of the crescent sun.  Good places to find pinholes are saltine crackers, your straw hat, and overlapping tree leaves.
Can you see the crescent suns in the lower right of the shadow?
Look at the sun filtering through the leaves of a tree on the ground underneath it.  Can you see overlapping images of the crescent sun?

You may also notice that shadows are a lot sharper and crisper as the sun's crescent gets smaller and smaller.  Because the sun is normally about half a degree on the sky, shadow edges are slightly blurry because light from all parts of the sun pass by the edge of whatever is making the shadow, but as the crescent gets smaller, the shadow edge gets crisper.  Because of this, the quality of the light is also very strange.  Look around you - it's darker but not like a normal twilight.  It's hard to describe, but you'll certainly notice the difference.  The air will get a lot cooler too.

If you have binoculars or a telescope with a safe solar filter, be sure to look for sunspots during the partial phases.  It's fun to watch the edge of the moon move toward the sunspots and "eat" them.

Also, notice how animals around you react to the eclipse.  As it gets darker, birds will return to their roosts and may start singing as they would in the evening.  We've seen porpoises dance in the ship's wake as they do in the morning and evening.

As I mentioned, the partial phase from first contact to totality will last about an hour and 15 minutes.  Use whatever safe viewing method you've chosen to check on the moon's progress every few minutes, especially if there are sunspots.  And take the time to look around and observe your surroundings.  How soon could you tell that something strange was going on if you didn't (safely) look at the sun?

As we are just a few minutes away from totality, the pace picks up and there's a lot to look for.  I'll cover this in my next post.

Tuesday, October 4, 2016

The Big Eclipse - Part 3: What to bring

Like the Boy Scouts, the eclipse chaser's motto is "Be Prepared."  Totality lasts a very short time, at most about 2.5 minutes depending on where you're viewing.  You won't have time to make decisions or wish you had another piece of equipment once the eclipse starts.  So it's important to have a checklist of what to have with you (this post), and a complete, well rehearsed plan for what you're going to do during the eclipse (a future post).

You probably have some of this already, but other specialty items like the solar filters and maybe even binoculars or telescope or camera lenses may need to be purchased in advance.

We've already covered the basic items for safe viewing in the previous post.  You'll need one or more of the following:

  • *Cardboard solar viewing glasses or #14 welders glass for direct viewing
  • Pinhole viewer of some kind such as described in my previous post
  • *Binoculars (both for projecting the partial phase, and direct viewing of totality).
  • Solar filters for binoculars
  • Solar filter for camera lens
  • Solar filter for telescope
* Must-have items in my opinion

In addition, you may want to consider the following additional equipment for viewing and imaging the eclipse.  I'll talk about photography in more detail in an upcoming post.
  • Small (40-80mm) telescope with solar filter
  • Camera with appropriate filter, ideally a DSLR with a 200mm or longer lens.  A focal length of 400 to 500mm is ideal. 
  • Video camera
  • Tripods for the cameras
  • A white sheet or tablecloth for viewing shadow bands (more about this in a future post)
  • Printed timetable of the eclipse customized for your viewing site.  Remember that the different parts of the eclipse happen at different times depending on your location.  Use the NASA map ( and zoom in on your viewing location.  Click on the map at your location and a pop-up will display all the important info for that location.
  • Accurate time source (most cell phones are good enough).
  • Sketchbook.  Some people like to draw what they see during both the partial phases (sunspots) and totality.  
Finally, there are several items you might want to bring to help you stay comfortable during the eclipse.  They include:
  • Chairs or blankets to sit on.  Remember that the eclipse lasts about 2 and a half hours from first contact to last contact.  A reclining lounge chair is a comfy way to view the whole eclipse.
  • Shade (an umbrella or canopy).  
  • A straw hat.  One reason for this is to keep the sun off your head, but the other reason is that straw hats form tons of pinholes for viewing the partial phases of the eclipse.
  • Plenty of water.  Hey, it's August and likely to be hot.  Snackage too.
  • Sunscreen and sunglasses (duh).  But remember, it's not safe to look directly at the sun through sunglasses.
That's pretty much all I can think of at the moment, but I'll go back and add things as I think of them.  As always, if you have questions or want advice about equipment, feel free to contact me.

Sunday, October 2, 2016

The Big Eclipse - Part 2: Viewing Safely

I was going to devote this post to a discussion about what to bring to the eclipse, but I realized that I can't really talk about what to bring until I've discussed viewing safety and the items you'll want to have for that.

First and foremost: never look directly at the sun (except during totality).  Don't look at it using your naked eyes, don't look at it through an unfiltered telescope or binoculars, don't look at it through an unfiltered camera.  The sun is no more dangerous to look at during an eclipse than normal, but people are more tempted to do so during an eclipse.  The only exception to this is during those few minutes or seconds of actual totality when the entire surface of the sun is blocked by the moon.  Even a very deep partial eclipse is not safe to look at.

However, the partial phases of a solar eclipse are really interesting too, seeing the outline of the moon creep slowly across the sun's surface.  So what can you do to view it safely?  Fortunately there are many options.  The easiest and safest is to use pinhole projection.  Basically you're building a simple pinhole camera.    Of course anything with small holes will work.  I've seen people use saltine crackers, and I've used my straw hat.

I'd recommend using a cardboard box with one side removed and a pinhole in a piece of foil at one end.  Here's a good link that describes how to build one:

Another safe way to view with slightly better image quality is to use a pair of binoculars to project the image of the sun onto a light colored surface.  Again, do not look through the binoculars.  Leave the lens cap on one side of the binoculars and aim at the sun with the eyepiece pointed at a light colored surface a few feet away.  You may need to adjust the distance between the binoculars and the surface to achieve good focus.

If you want to look directly at the sun, you'll need a safe filter.  Examples of safe filters include #14 welder's glass and aluminized glass or mylar filters specifically designed for solar observing.  Do not use sunglasses, film negatives, smoked glass, or neutral density filters.  Do not use space blankets or other aluminized mylar not specifically manufactured for solar viewing.

Safe solar filters come in several forms.  There are the cardboard "eclipse glasses" for naked eye viewing that are available from many online sources.  I strongly recommend that you buy a few of these regardless of what else you get.  They are relatively inexpensive and it's really cool to see the partial phases of the eclipse directly using those glasses.  Just Google "eclipse glasses" to see your purchasing options.  If you're local, I have quite a few extras that I'm happy to share.

If you want to try photographing the eclipse (the subject of a future post) or viewing through a telescope or binoculars, you'll also need a solar filter that fits snugly over the end of the camera lens, telescope, or binoculars.  There are many suppliers for these filters, but I like Oceanside Photo and Telescope:  Look for a filter that is slightly larger than the outside diameter of your lens or telescope.  You may need to add some foam tape to the inside of the filter for a snug fit.

If you have specific questions or want help choosing a filter, please feel free to contact me.

This is really just a summary, and an excellent article on safe viewing can be found here: and I'd strongly urge you to read it.

Saturday, October 1, 2016

The Big Eclipse - Part 1: Where to go

By now you've all probably heard that there's going to be a total solar eclipse visible across the US on August 21st of next year.  The news stories started appearing almost a year ago, and the coverage has been getting more intense every month.  I've actually been looking forward to this eclipse since I first found out about it about 15 years ago.  This is one you definitely don't want to miss; I've seen 2 total solar eclipses (and been clouded out for a third), and they are one of the most amazing spectacles of nature that you'll ever witness.

Because I've been getting so many requests for advice about the eclipse, I thought I'd cover it here in the next 3 or 4 blog posts.  I'll cover topics including where to view, what to bring, how to safely view the eclipse, and what to expect during the eclipse itself.  This particular post will focus on where to view since it's not too early (and may be too late in some cases) to start planning your travel.

Let me first say that unless you happen to live in the narrow (about 60 miles wide) path of totality, you won't see a total eclipse.  Rachel compares a total eclipse to being pregnant.  It's either total or it's not - there so such thing as "mostly total".  Even if you live close to the path of totality, you'll only see a deep partial eclipse which is absolutely, completely, and in every way NOT a total solar eclipse.  If you're even slightly considering not traveling into the path of totality, please contact me so I can talk you out of it.  Please.  So, most of us are going to need to travel.  But where?

NASA has a wonderful interactive Google map showing the path of totality here:  As you can see, it stretches across the US from Oregon through the midwest, and leaving in South Carolina.  It passes over some major cities such as Salem, OR, Idaho Falls, ID, Jackson and Casper, WY, Kansas City (barely), Columbia, MO, Nashville, TN, and Charleston, SC.  The other important point to note about this map is that the closer you are to the centerline (the red line on the map), the longer the eclipse will be.  The 2 blue lines show the limits of totality, but if you're right near that blue line, you may only see a few seconds of totality as opposed to around 2 minutes at the center.  So as you think about a location, choose one close to the centerline if possible.

Weather is also a consideration.  Fortunately August is generally pretty good weather-wise across most of the path of totality.  But of course some places are better than others.  A good set of maps and charts describing historical cloud cover for August can be found here:  For those in Oregon, Salem actually isn't bad, while the coast is riskier (but it would be amazing to watch from the beach).  Of course these are only averages, and the weather on the actual eclipse day could be anything.

Your next decision is whether or not you want to try and stay somewhere overnight or just drive on the day of the eclipse.  In Oregon, the eclipse starts around 9am, with totality about 10:20 am.  If you live close to the centerline, this gives you plenty of time to drive to your location, watch the eclipse, and drive home the same day.  This means no overnight accommodations are needed, and you can change your destination at the last minute in case of local clouds at your chosen spot.  However, if you plan to view more than a few hours from home, you'll probably need to travel the day before and stay overnight.  Unfortunately many (most?) hotels and campgrounds along the centerline are already booked.  But that doesn't mean you can't try.  You can also try to book lodging an hour or 2 away from centerline and drive to your viewing site that morning.  But if you do plan to stay overnight somewhere, start making arrangements now.

OK, you've decided approximately where you're going to be.  But where, exactly, are you going to view from?  Fortunately the sun will be fairly high in the sky for everyone in the US, so you won't need to find a place with good views to the horizon. I recommend a nice grassy park somewhere, but anywhere will work.  We watched an annular eclipse from the balcony of a motel a few years ago.  The entire eclipse from beginning to end lasts a little over 2 hours, so if you're going to watch the whole thing, be sure to pick someplace that you can stay around that long.  We have also found it really great to view with a crowd, especially if some of them have telescopes fitted with a solar filter.  Check with science museums and astronomy clubs in your area to see where they are having viewing parties. But be aware that organized events like this are likely to be very, very crowded.  Again, a public park might just be perfect.

In my next blog, I'll discuss what you might want to bring to the eclipse.  Some items like solar glasses are a must and may be in short supply, so you'll want to order some soon.  In the mean time, if you have questions, post them here and I'll try and answer them.

If you're local and would like to find out more about what it's like to see a total solar eclipse, we have a great video (on VHS!) made during the 1991 eclipse in Mexico that really does a great job of communicating the excitement of a total eclipse.  This was my first successful solar eclipse, although we viewed it from a ship off of Mazatlan.  If you have a VHS player, you're welcome to borrow it.