Little Black Spot

Observing notes from the afternoon of Monday, November 15, 1999

How does that song go? "There's a little black spot on the sun today". Well, that's exactly what happened in the late afternoon of Monday, November 15, 1999. That's when the tiny, silhouetted disk of Mercury could be seen transiting the face of our local star, the sun.

The day before I constructed a solar filter for my 80mm refractor. I used the new solar material, from Baader, that I purchased from Astro-Physics. This stuff is like your typical Mylar filter, which looks and feels like a thin sheet of tin foil. But I think it is made of a different material. I found it very hard to cut, even with a razor blade. I made the filter cell out of cardboard. It doesn't look that great, but as I found out during the transit, it performs wonderfully.

I went into work a couple of hours early on Monday so I could leave early enough to beat the traffic and arrive at my observing location at a decent time. The location was Ebenezer Church Recreational area on Jordan Lake. This is a beautiful spot and gave a great, mostly flat horizon for the observing. I was joined by co-worker and observing partner Michael King. He had his Meade 90mm ETX Maksutov and was using a glass solar filter made by Thousand Oaks Optics.

After setting up the scopes at the water's edge, and donning the solar filters, the immediate surprise was the number and size of sunspots. They were fabulous! This was my first time observing with a solar filter (besides quick peeks through other scopes). I've always used solar projection and hadn't even done that in about 7 years. There were sunspots all over the place. And they had such interesting and unique shapes. They were very dark in the centers, surrounded by lighter colored outer areas. It kind of reminded me of looking at lakes and rivers from the air. The lighter areas resembled the shallow waters and the darker areas resembled the deeper waters. White areas, which I assumed were solar flares, could be seen in various spots over the solar disk. Although less prominent than the sunspots, they were just as interesting in size and shape.

We also compared the views between the two filters. The Baader material presents a sun that is kind of yellow-white in color. The Thousand Oaks filter had an orange colored sun. While I think the orange colored sun is prettier, I think the Baader filter gave better contrast and more detail. Just for the record, Michael thought the Baader filter gave a light, bluish or grayish color.

We began looking for Mercury just before its predicted first contact time. The seeing varied a lot. Sometimes the sun was nice and calm and at other times it was boiling. The edge of the sun was wavy or saw-tooth. I was worried that we might not immediately see Mercury. But then I notice that one of the little black notches was not moving. It was Mercury! Slowly and surely, the little planet made its way in front of the solar disk.

I'm not sure if we saw the "black drop" effect or not. Even after Mercury had moved in front of the solar disk, there did seem a time when it was still connected to the edge. From this evidence, I would tend to say that we saw it. But, as I've said, the seeing varied a lot and was constantly getting worse. For those of us in North Carolina, this transit was happening right at sunset and the sun had actually set before the transit was over. Even so, we did enjoy seeing the entire disk of Mercury in front of the sun for a little while.

I'm ashamed to say that I found the sunspots a little more exciting than the Mercury transit. I guess I'm just not use to observing sunspots in such great detail. Mercury was, after all, just a little black dot on the sun. The excitement was still there. This basically came from knowing that the little black dot was the innermost planet, crossing in front of our local star, which itself is about 93 million miles away. And as it moved along in its orbit, it confirmed that the solar system is quite a dynamic place.

As the sun dipped closer to the horizon, the image got more orange and red and bloated (or more like squished). The turbulence could be seen along the edge of the sun and it appeared as ocean waves. Wave and wave would venture across, some of them distorting the image enough that Mercury would vanish. Finally, the sun was low enough that Mercury was totally lost in the quivering image. But we were still treated to a beautiful sight. As the sun slipped below the horizon, the distant trees were seen in silhouette. Also, flocks of geese and other birds flew across the sun heading for their nightly roosts. Finally, the sun slipped entirely below the horizon and was gone.

It was so peaceful. The entire time I could hear the waves of the lake, lapping at the shore and feel the cool breeze as it came across the water. The western sky was a fiery red and reflected on the lake like shimmering coals in a dying campfire. The sky overhead was deep blue while in the east, the shadow of the earth began to rise. A first quarter moon hung in the southern sky. This was my first transit and I enjoyed it immensely. Now I'm ready for the next planetary transit which will be Venus in a few years, and again we will see a little black spot on the sun.

Jeffrey L. Polston

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