WHAT IS THE BOTTOM LINE FOR CALENDAR CURVES?
Declination lines or curves are always symmetrical about the SD (style distance line). They only look non symmetrical on dials such as the east and west decliners because about half of the dial is always missing. IE an east dial has no afternoon hours, a west dial has no morning hours. Thus a declination set of curves for lat 32 is the same as lat -32. In other words, the sign can be ignored on SH, since SH is always above the dial plate, and SH (style height) is the latitude for declination or calendar curves. Not true for SD, style distance, because it may be either side of the vertical. The use of SH for the apparent latitude for the calendar curves is important because… 1. A dial plate is merely a presentation device for shadows, and thus is a geometrical mapping of the sun’s circular movement to a plate that displays it. 2. This shows further an important point, namely that with correct alignment, altitude and azimuth are portable, an issue I discuss towards the end of book 2. T
