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Eclipse data by Fred Espnak, NASA GSFC. (full map)

 

CAUTION:
Serious eye damage could occur by looking directly at the sun without using a proper solar filter.

 

ANNULAR SOLAR ECLIPSE - MAY 20, 2012


A solar eclipse occurs when the moon passes directly between the Earth and sun. If the moon is close enough, observers on the centerline are treated to a spectacular total eclipse revealing the corona and solar flares. However, if the moon is at a farther point of its orbit, as it will be during the May 20 event, it is not big enough to completely blot out the sun. At maximum eclipse, a thin ring (annulus) of blinding light remains when viewed from on a very near the centerline. The image above is from the May 10, 1994 annular eclipse I photographed in El Paso. That centerline narrowly missed Arizona's southeastern corner, but now 18 years later, a solar eclipse centerline will finally pass over our state. I say finally because the last time we saw one was on August 27, 1821.

The map at left, from the NASA eclipse website, shows the eclipse centerline (in red) cutting across the northeast corner of Arizona. People located along this line would see a perfect ring at maximum eclipse (see centerline image below). Moving out towards, but staying between, the blue lines would cause the moon to shift while still remaining totally within the sun's disk (Four Corners). Observing from just inside the blue lines would cause a side of the solar ring to almost disappear (Sunset Crater). Moving outside the blue lines, such as at Flagstaff, changes the view to a partial eclipse. I included the view from the Yuma area because that represents the least amount of maximum eclipse that will be seen in Arizona. Notice that moving north of centerline shifts the moon south (left), while the opposite occurs as you travel south of the centerline.

Eclipse Times will all be in the late afternoon for Arizona. First contact should be a few minutes either side of 5:30 PM MST (depending on your location) with the sun about a quarter way up the western sky. Maximum eclipse will be a little more than an hour later and the show will end when the sun sets in the WNW. To find your local details, go to the May 20 eclipse page on the NASA Eclipse Website. You will see a map window with eclipse path. Navigate to Arizona and zoom in as much as you want. Clicking on the map brings up a window showing the times of all eclipse phases visible from that location. All times are based on a 24-hour, Universal Time (UT) clock. Subtract 7 hours to get Arizona Time (MST) or 6 hours if you go by Daylight Saving Time (MDT) used on the Navajo Reservation where the centerline mostly lies. The information window also includes the sun's altitude and azimuth for each eclipse phase. See my Navigating The Sky page if you are unfamiliar with these measures.

Viewing The Eclipse will require the use of a filter to block the sun's harmful rays that can cause severe eye damage. Look for inexpensive eclipse glasses from certain local outdoor/nature shops or telescope stores. Also try any science center, planetarium or observatory in your area. There are several online sources, one being the Rainbow Symphony Store. Observing through binoculars or telescopes require larger filters to place in front of the optical device. Thousand Oaks Optical has just about everything you could need including a 12"square piece of material you can use to make your own filters.

An eclipse unfolds very slowly. I always like to catch the moon taking its first bite out of the sun. Then it only takes some occasional glimpses skyward to see the progression. After a while you should start to notice the world isn't quite as bright as usual. Examine your surroundings, with glasses off, to look for crescent-shaped spots of light. Small openings in foliage and all sorts of objects act as countless pinhole cameras, projecting the shape of the light source. We see these projections quite often, but don't notice because of their usual round shape. Think of how strange they will look when the sun is a ring shape during the annular phase.

The sun will be fairly low in the sky at maximum eclipse. The usual slight dimming of sunlight at that time of day will add to the much stronger effect of the eclipse to create an early twilight. Eclipse twilights are eerie in that the sun cast sharp, though very weak shadows. Normally twilight is a time of very soft lighting.

After maximum eclipse, the sun's slow brightening of the landscape will be lessened by atmospheric dimming as it nears the horizon. At sunset, you can take off your eclipse glasses and watch just like any other sunset. Don't stare, just take short glances. If the sun seems uncomfortably bright to your eyes you can always put the glasses back on. All that refers only to naked-eye viewing. You should never look at the sun through any optical device (binoculars, telescope, etc.) without a proper solar filter no matter how low it is in the sky or how dim it appears.

Photographing The Eclipse can be as simple or as involved as you want. The easiest view to get is when the eclipsed sun is setting. For this kind of photo I usually take a light reading of the sky directly adjacent to, but not including, the sun. Then I might bracket the exposure to make sure I got what I want. Any kind of film or digital camera will work fine and a slight to moderate telephoto will add to the impact. Below are some representative views showing how the sunset will appear for various areas of Arizona. The very northwest corner of the state will see the least amount of eclipse while the southeast will enjoy the greatest.

Shooting the sun other than at sunset requires a filter. I have used a Kodak Wratten 4.0 Neutral Density (ND) gel filter on camera lenses for many years. It works great for photography, but is not safe for viewing--including directly through a DSLR viewfinder. A good alternative to an ND filter is a Black Polymer (BP) filter from Thousand Oaks Optical. They offer these in threaded filter mounts in popular sizes from 37mm to 82mm and a 12-inch square sheet. Since BP is safe for viewing and photography, you could buy the sheet and make a camera filter and also some filters for general eclipse watching. I made a camera filter by cutting a rectangle of matte board to slip into a Cokin filter holder. I cut a hole in the matte board and just taped the filter material onto it.

With a 4.0 ND filter, I would regularly use exposures from 1/125 to 1/250 at f/11 (ISO 100). BP is a darker material and I've gotten useful images at exposures from 1/4 to 1/30 of a second at f/8 (ISO 100). Our brains want to see an orange sun like we do at sunset. ND filters, being neutral as their name implies, give a weak yellow color, especially with digital. The BP filter imparts the desired orange all by itself, even when technically overexposed a stop or two.

I mentioned a range of exposures since they depend on the rendition you want. When using a moderate or longer telephoto lens, the solar image will be large enough to make it worthwhile just exposing for the sun and picking up any sunspots and the edge darkening. Nothing else will be recorded so the sun will be seen against a black sky. That's when to use the darker exposures.

Another rendition is to combine the solar sequence with a dusk scene, such the one seen at left. This shows a sunset partial eclipse from June 2002 I photographed from South Mountain Park. Think of what it would look like with more extreme crescents and a perfect ring about midway up.

When you try making an image like this in a single frame, you always want to make sure you give the suns enough exposure to completely overpower the sky background. If not, the ones that appear up in the blue sky might come out dim and have a slight blue cast. This situation is the time to use exposures in the brighter part of the range I mentioned. If you take separate exposures with the intent of combining them later in an image editing program, you could go with the darker exposures and brighten them as needed. Whether using single or multiple frames, keep the camera locked down on a tripod and and shoot a progression of the sun. I find an interval of 5 minutes between exposures gives good spacing (like in the shot above). Then, about 20 to 30 minutes after sunset, make an exposure of the sky and landscape.

The exposures given above for ND and BP filters are a starting point. This is an involved image to capture and many things can go wrong. You should try some dry runs on the setting sun prior to eclipse day to work out your procedure. Whether you try a sequence or just stick to a sunset shot, this eclipse is a great chance to make some exciting images.


All images are copyrighted by Frank Zullo. Please do not use without written permission.