Planar Sundial


This frame has calculations for the general planar sundial. It will calculate the sundial major hour angles for any vertically and horizontally rotated aspect surface. The Planar Sundial will calculate any plane surface sun shadow for any angle of gnomonic declination, angle to zenith, any longitude, latitude and for any time of year. Also shown is the equation of time and longitude correction factors.


Polar format output


Rectangular format output



Equation of Time Plots


As an interesting side note, the shortest day, latest sunrise, longest day, earliest sunrise do not correspond to December 21st and June 21st as one would assume. Due to the elliptic nature of the earth's orbit about the sun and the analemma it makes in it's daily position in the sky means that the sunrise min max and sunset min max fall on days before and after the equinox. See this site for more: Dark Days on the USNO.NAVY.MIL site. My calculator can figure this for you by working the dates forward and backward fro the equinoxes to see for you self.


Any normalized ( i.e. delta for daylight saving) time position of the sun thru the year. 



This next one shows the suns position thru the year for each of the hour angles. So in the morning and evening the analemma lay on it's side and the top and bottom of the year (equinoxes) do not touch the horizon first. This is what creates this effect.



Graphics Examples courtesy Dover Books

False Analemma (only angle is preserved not outline.


Graphics Examples courtesy Dover Books

True Analemma offsets for angle preservation




Graphics Examples courtesy Dover Books

Cube surface sundial


Graphics Examples courtesy Dover Books

Analemma Sundial Example


Graphics Examples courtesy Dover Books

Another many surface Sundial Example




My First Pocket Sundial

I used a nice piece of interesting Oak I had from pallets. After planing and dimensioning

I next scanned the images and printed on tracing paper (vellum) and used Elmers Wood Glue to attach and then clear acrylic sprayed the inside face. I "Golden oak" stained the outside after sanding and beveling the outside. Then coated with the same clear acrylic spray. 



My AstroCompass

got this beauty at garage sale for $15. Worth $300



The box has since been refurnished and looks all new.

I'll have to get this updates.

AstroCompass Manual - PGE's site with a manual for the AstroCompass