Wednesday, May 23, 2012

Stared at sun, had fun...

As promised, my dad, younger brother and I wandered down to southwestern Utah, placing ourselves in line with the center of the eclipse - and waited.

Rather than contend with hoards of people descending on well-publicized towns like Kanarraville - almost exactly in line with the eclipse but conveniently located just off Interstate 15 - we headed toward a small almost/former town of Modena located a few miles east of the Utah-Nevada border.  Driving west from Cedar City, Utah on highway 56 we noted that pretty much all of the passenger car accessible side roads and turnouts were occupied by people who seemed to be readying themselves for the event that was to occur just 3 hours later.

Upon reaching Modena, we drove through the town and considered stopping there, taking advantage of the trees and desolate, picturesque landscape and partial ghost town and were somewhat surprised that we didn't see anyone else obviously set up to witness the event.  We decided, however, to continue on the highway and a few miles down the road we left the pavement and followed a well-graded dirt road into the surrounding, low mountains.  After a few miles - and passing one or two other places where people were setting up to stare at the sun - we found a wide area that was excellent both for viewing and throwing our sleeping bags on the ground for the evening.
Figure 1:
Setting up the 8" telescope with sun filter.
Click on the image for a larger version.

With about 2 hours to spare before the first bite was to be taken out of the sun, we lugged our gear about a hundred feet further south to clear a nearby brush-covered ridge and I began setting up my old 8" Celestron reflector telescope, outfitting it with a Baader filter in a homebrew, cardboard mount to enable safe viewing.  Soon, the eyepiece revealed a boiling, bespeckled sun and we then proceeded to set up the rest of our gear.  Soon after this, Gordon, K7HFV arrived having driven down under separate cover.

I had with me an adapter that would convert the 1-1/4" eyepiece mount to a standard Pentax "K" mount and my brother had the foresight to order an adapter that would permit mounting of his Sony DSLR.  With this arrangement we were soon projecting a live image of the sun directly onto his camera's sensor, using the "live view" function to focus the resulting image as precisely as possible.  As expected, only about 80% of the sun's disk would actually fit onto the imager so any "full-disk" pictures had to be taken in two, overlapping parts, adjusting the telescope slightly for each, the pair of images to be pasted together later.

Figure 2:
A solar projecting telescope used to monitor the eclipse.
Click on the image for a larger version.
I had with me a small power inverter to run the telescope's AC tracking motor (I said that it was an old telescope!) and not having set its mount up perfectly, we had to occasionally bump the right ascension to re-center the image, but this was very easy to do - especially considering that we were constantly moving things back-and-forth to get full-disk images, anyway.

One thing that was apparent from our drive in was that there was quite a bit of airborne dust without very much wind, a phenomenon attributed to wildfires burning a few hundred miles south in Arizona.  As the sun set in the west the sky became brighter as the sunlight was scattered by the dust and in our telescope, the image of the sun was slightly fuzzier and less stable than we'd hoped with the sunspots popping in and out of sharp focus randomly. In the images seen through the eyepiece - and on the camera - we could also see a bit of fluctuating colored fringe - something we attributed to atmospheric refraction as the reflector telescope itself should not have imparted a visible degree of chromatic aberration on the visible image by itself:  This effect seemed to increase slightly as the sun's angle dropped toward the horizon.

Within a few seconds of the time predicted, we could see the first bit of the moon's encroachment onto the sun's disk and at about that time (6:26 PM local) I measured the solar intensity as being 84200 lux - a value approximately one third of what one might see during local noon on a clear, summer day.

Figure 3:
The back end of the solar projecting telescope with a solar crescent.
There is a green filter in the optical path to reduce chromatic
aberration.
On the day before the eclipse (Saturday, 5/19) I'd put together a few simple devices for the safe viewing of the eclipse.  One of these was a "solar projecting telescope" seen in the picture above.  This device consists of a double-convex lens at the far end of the tube immediately followed by a pair of "Kelly Green" theatrical gel filters followed by one "Fire" red gel element.  About 1/4 of the way from the "Sun End" of the tube was a strong, plano-concave lens that then spread the image out a bit before hitting a ground glass screen that I'd installed about 1/5 of the way up from the "Eyeball" end in which I'd installed another double-convex lens to permit either direct viewing of the image on the ground glass screen, or a magnified view of that image when viewed from a few inches away.  As can be seen from the picture, a shroud was placed over the tube both to shield the viewer from the direct sun and to aid in aiming by adjusting the device on the tripod so that it cast no shadow on the backside of the shroud itself.  As you can see from the picture, it was all assembled into a stiff, cardboard tube with the lens, filter and ground-glass mounts being constructed of scraps of cardboard and black posterboard held together with thermoset ("hot-melt") and yellow wood glue!

Figure 4:
The moon, encroaching on the sun's disk.
Click on the image for a larger version.
This telescope wasn't intended to provide a crystal-clear image - and it didn't, as can be seen from the above picture - but it was a safe, convenient way to get a quick, safe glance as the current phase of the eclipse.


As the event progressed, it started to get darker as evidenced by the lower lux readings on my light meter.  While it still seemed to be plenty bright, there was an eerie aspect to the illumination of the surrounding landscape that defied description:  Was it the increasing sharpness of the shadows as the sun's disk was reduced in size, or was it the gradual loss of contrast between the highlights and the shadows or was it largely psychological, with the increasing incongruity between the brightness of the landscape and our expectation of what it should look like at that time of day?

Working the camera and telescope, my brother continued to snap pictures every minute or two as the moon made its way across the face of the sun, gradually blocking the visible sunspot groups as it did so.  The rest of us occasionally snapped pictures of each other, the surrounding landscape, and made various attempts to take our own pictures, sans-telescope.

Figure 6:
The "ring of fire" observed during the peak of the eclipse.
Click on the image for a larger version.
At about 7:33 pm local time, the entirety of the moon was contained within the solar disk and the landscape was eerily drab, the colors seemingly muted and the air suddenly seeming cooler than before.  At this point my meter indicated a reading of 3570 lux - a brightness of about 4% of what it had been just prior to the start of the eclipse and roughly comparable to what might be seen in a well-lit room:  To be sure, at least some of this decrease would be due to the lower angle of the sun in the dusty atmosphere.

Resisting the temptation to do so, we avoided sneaking a peek at the sun during the "ring of fire" phase of the eclipse knowing full well that within the ring of sunlight, the light was just as bright as it normally would be - the difference being that a ring would be burned onto the retina rather than a circle!  It was during this period of maximum occlusion that by brother was furiously snapping pictures - one of these being visible to the right.  As can be seen, our location put us almost exactly (within a couple of miles) in the center of the path forming a nearly perfect ring of sunlight around the moon that was visibly changing by the second!  Impressively, in many of these pictures picture one can make out "jaggies" along the edges  from the lunar mountains.

Figure 7:
The last seconds of the annular eclipse.
Click on the image for a larger version.
Too soon, the moon finished its traverse across the sun's face, extinguishing a narrow ribbon of sun along the edge as it did so - a scene captured in the image to the left.

Gradually, the eerie darkness of the landscape was replaced by the warm glow of sunset as the moon moved away from the sun's disk while setting on the western horizon.

In the gloaming, we relocated the telescope to the immediate vicinity of our cars and ate the snacks that we'd brought with us.  Later that night, I pointed the telescope at familiar night-sky objects such as the thin crescent of Venus and the rings of Saturn accompanied by several of its moons.  After putting the equipment away for the night, we bedded down under the stars, occasionally waking to glimpse the rise of the Milky Way as we spun our way toward the sunrise.

In the morning we got up, packed our gear back in the cars and headed off toward Cedar City where he had breakfast before heading back north to Salt Lake.

* * *
Figure 8:
The happy Eclipse God!
Later, I heard from my friend Ron, K7RJ who had been several miles to the east of us, also along the center line of the eclipse, just off highway 56 short of Modena.  There, he had also witnessed the spectacular sight with is wife Elaine, N7BDZ.  Unlike us, they both had plans for the following day (Monday) and they started back to Salt Lake a bit after the eclipse.  What would normally have been a 4 hour drive turned into a 6 hour drive as hoards of eclipse glimpsers - all with the same idea - clogged the 2-lane northbound interstate on their return trips, but he arrived home safely, albeit a bit later than expected.

Clearly, the Eclipse God was smiling upon us, granting us clear skies and safe travels!


* * *

Credits:  All of the telescope-based pictures of the sun/moon were taken by my brother while the picture of us at the telescope was taken by Gordon.  Those of the solar projecting telescope were taken by me while Ron provided a picture of the happy eclipse god.

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