The twice-a-year sun transit event at St. Margaret’s, when the sun comes at the precise angle to cause an image of the east window cross to appear in perfect position in the center aisle, will climax this Tuesday, March 13 at 8:42:17 a.m., PDT. You are invited to stop by to view an amazing sight, pray, take pictures, and marvel at the beauty and precision of the universe God has made. The building will be open no later than 8:15 a.m. for viewing.
The next time this will happen is Friday, September 29, 2018 at 8:24:18 a.m., PDT.
The sun comes straight through the east window of the church (as measured horizontally), and the cross and center mullions cast a shadow on center points of the aisle and the west end of the church when the sun is positioned at 108.04° azimuth as measured from a fixed land position of 33.70351º latitude and -116.39804º longitude, near the center crossing of the church. Similarly, the sun comes straight through the south window of the church and casts shadows toward the north at a solar azimuth of 198.04º.
The vertical position of images and shadows cast on the west end of the building is determined by the solar elevation. When the sun is centered at 108.04° azimuth, it creates an image of the arched east window, including a purple image of the cross from that window. Significant solar elevations include the following:
- 9.12°: Top of arch at top of crown molding in choir with cross image against the back wall of the choir
(a bit too high to be aesthetically pleasing)
- 9.44°: East window image at ideal height for viewing the cross image against the back wall of the choir
- 9.52º: East window image at minimum height for viewing the cross image in an aesthetically pleasing way against the back wall of the choir
- 9.58º: East window image at the extreme minimum height for viewing the cross image against the back wall of the choir
- 18.79º: Top of cross image at the meeting of the predella and the floor; not aesthetically pleasing because the window image extends onto the predella
- 19.26º: Top of arch at the meeting of the predella and the floor; not aesthetically pleasing because the cross image extends forward of the center carpet
- 19.8º: Top of cross image at the forward edge of the carpet; not aesthetically pleasing because the window image extends forward of the center carpet
- 20.25º: Top of arch at the forward edge of the carpet: IDEAL VIEW
- 22.18º: Bottom of cross image cut off by shadow of balcony toward the rear of the first pew in the rear section;
highest solar elevation at which full cross image can be see centered in the aisle
The cross in the choir is best photographed from the center aisle, standing in the front section of pews. The photographer’s shadow will fall below the frame of the photograph. The cross in the center aisle is best photographed from a high point (e.g., a ladder) far back in the center aisle or standing further forward in the center aisle, taking care not to cast a shadow into the frame. A position in the balcony will cast a large shadow into the frame.
Optimal Viewing Dates
The best viewing dates and times always arrive on March 13 during the Spring, between 8:41-8:44 a.m. PDT (an hour earlier when in years when Daylight Saving Time hasn’t yet begun, such as 2021); and on September 29 or 30, between 8:22-8:25 a.m. PDT. The actual peak viewing time varies year to year. How do we know these times? Because the Rector is an astronomy geek, and sat down and calculated the peak viewing times through 2033!
See the full schedule of upcoming solar shows at St. Margaret’s at http://www.stmargarets.org/facilities/sun/.