Michael Hotka's

Analemma Viewer Setup and Use

I found an area in my backyard where I could setup my viewing location and not have it be disturbed for a year.

To align the viewer with the celestial North Pole, I put a stake in the ground, where one alignment nail will be. To find the placement of the second alignment nail, I hung a plumb bob vertically, sighting both this pole and Polaris at the same time on the vertical string. My wife, Barbara, inserted the second nail just under the place the plumb bob was marking. These two nails marked the celestial North direction.

A view of the night time alignment setup in the daytime. Notice the second alignment nail is already in place that Barbara helped me place the night before.

I aligned two concrete pavers that will support my Analemma Viewer. I stretched a line between the two nails marking the celestial North direction. I then aligned the two concrete paves on this alignment string.

With the Viewer in place, I aligned the edge of the Viewer, so it's edge was parallel with the 2 concrete pavers. Then I used a black Sharpie to mark where the Viewer's feet should be placed each time I setup the Viewer in the future to take a reading of the Sun.s position.

The Viewer ready to take a reading of the Sun's position, 21 seconds after local noon. The 21 seconds was necessary because of my longitude line in relation to the center of my time zone where local noon is truely straight up noon.

The Viewer on the last day of observations, November 12, 2017

A close up view of the last reading on November 12, 2017. The Analemma was supposed to be contineous, lining up, but a bit behind (a leap year effect) the dot placed there on November 12, 2016. What I suspected happened was the fact that I releveled my viewer about every 2 months. This showed that the dirt under my concrete pavers moved a bit. What I didn't do is to check the celestial North alignment about August 2017. This is when I believe (and can be seen in the plots of Activity #4) that the ground may have twisted the convrete pavers, and hence my Viewer, in addition to the rise and fall of the dirt under the pavers. That would account for the final reading being off as it is.

Note from this image that it is very important to note the date of the Analemma solar dot. This is important to know when reducing your observations to get the values of the Tilt of the Earth's Axis, your observing latitude, the Equation of Time and the Eccentricity of the Earth's Orbit.

If I were to do this again, I would check the level AND celestial North alignment every month to ensure that the Viewer is in the correct orientation to make accurate readings of the Analemma.