Sundial slides

Summary

1) The location of the temporary plaque, next to the stairs, has worked well for more than two years Slide 1 2) A proposed location on the north side of the gnomon has several shortcomings:  a) The plaque is always in the shade.  b) On a sunny day, the sun hits you in your eyes as you face south and try to read the plaque Slide 4.  c) Standing in this location, you are blocking other people who are trying to read the sundial in the middle of the day Slide 4.  d) The long, narrow format is not as easy to read as the more common rectangular formats seen in Slide 2.  e) Finally, if a plaque were mounted, or needed replacement, or vandalized, on the 109 year old concrete gnomon, the gnomon could be damaged and the sundial accuracy ruined. This would be very difficult or impossible to repair. The gnomon needs to be precisely aligned in all three dimensions. Concrete benches in Sundial Park have needed replacement or repair, other concrete benches along the border of Ingleside Terraces at Ashton Avenue are missing or broken and the concrete gnomon could have the same problems, see damaged benches and gateways.

Slide 1

1 In June, 2020, I found that the 1914 Sundial booklet said that there was a plaque at the Ingleside Terraces Sundial that gave the minutes that must be added or deducted from sundial time in order to get local clock time [the "equation of time"]. The plaque had been missing for many years. I put together a temporary plaque and we installed it at the entrance to the Sundial to the left of the stairs. A larger plaque, or plaques on either side of the stairs, could be installed, without any risk of permanently affecting the original sundial. This is the main entrance to the sundial, as it is the only location with stairs and sidewalk blocks, which lead to the 1913 marble plaque and the gnomon. According to the 1914 Sundial booklet, page 9, "There are several entrances to the sundial park in Ingleside Terraces, but by far the best way to view the spot in all its beauty is from the entrance to the south".

July 22, 2020. For another view, see Fax_Art

Slide 1a

1.a.Just behind the stairs are four concrete sections, each measuring 2 feet x 2 feet. There is space for ground level plaques, similar to the Hollywood Walk of Fame or the Castro Rainbow Honor Walk. The accompanying photo shows this proposed location, with a plaque on the left to be used for historical information, and a 17"x14" plaque on the right used for the table giving the minutes to be added or deducted from sundial time to obtain local time. Larger plaques could be installed if needed. Right click and use the (+) sign for a larger image (the photo of the chart has an orange streak that occurred in the printing). The worn marble plaque, that is seen at the base of the gnomon, gives the October 10, 1913, dedication date of the Ingleside Terraces Sundial. A new plaque with the equation of time could possibly be placed in front of the marble plaque. 1921 plaque in the brick sidewalk at 1st and Market, San Francisco. Right click and use Ctrl+ for a larger image.

Slide 2

2 This is the sundial chart that we developed. It has several user friendly features. The times are arranged in two minute intervals, so that the time adjustment can always be read within a minute, which is the limit of accuracy for a sundial. This chart is more accurate than the traditional plaque below (data upon request). Numerical data is from NOAA. There are 43 date and time entries. It gives instructions on how to use the chart and how to read the Ingleside Terraces sundial. There is information about the sundial and the San Francisco Landmark number. The sundial equation of time charts with two minute intervals are Copyright 2021.

Slide 3

3 For comparison, here is a plaque from New Zealand. It is a nice plaque, but it doesn't contain as much information as our plaque. It has the typical Equation of Time chart. The time adjustments are shown three times a month, which creates odd intervals. For example, in February, three different days have the same time adjustment. But there are other dates that have a four, five, or six minute gap, which makes it more difficult to attempt to read the time adjustment to the nearest minute.

Slide 4

4 Here is the location on the north side of the gnomon that we discovered after searching through old photos. A plaque on the north side of the IT gnomon is always in the shade (unretouched photo with a sample printout of an 8"x30" plaque). If you come by in the middle of the day, which is the best time to read a sundial, the sun will hit you in your eyes as you face south and attempt to read the plaque. A 8"x30" plaque is narrow and tall, would extend from approximately 4 feet to 6.5 feet above ground level, and be more difficult to use and contain less information than the smaller plaques in Slide 1.a. or Slide 2. Right click and use the (+) sign for a larger image. Standing at this location, you are blocking other people from reading sundial time. The original plaque has probably been missing for more than 90 years. Its exact content is unknown.

It is more difficult to photograph a backlit image, which may explain why we never found a closeup photo of the original plaque. AFAIK, this is the only sundial in the world with the plaque on the north side of the gnomon in the northern hemisphere (or on the south side of the gnomon in the southern hemisphere).

Slide 5

5 I have a website with many pages about sundials. Several of my webpages are ranked very highly on Google. As you can see in the recent screenshots, my webpage on Sundial plaques ranked number one in a Google search for that topic, out of 623,000 results, and my webpage on Sundial accuracy ranked number two, out of more than eight million results!
	Google searches 10/9/2021 on a PC

Slide 6

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	Our Ingleside Terraces sundial is a working, surprisingly accurate sundial, not just an historical artefact. We want a plaque that will best serve another generation. A permanent sundial plaque should be placed next to the stairs, see Slide 1, as this location is at the entrance to the sundial, is most visible, is in the sunlight, does not interfere with users of the sundial, there is no risk of damaging the sundial, and there is room for user friendly, informative plaques.