Solar Motion, Position & Time Measurement Instrument - Northern Hemisphere

These are the northern-hemisphere components.  For the southern hemisphere, you will need this model instead:  Solar Motion, Position & Time Measurement Instrument - Southern Hemisphere by 3DMason | Download STL model | Printables.com

Change History

Update (14-11-25): (Optional) A 0.5 mm oculus vs. the original 1.0mm is now available; i.e., Clock_Hybrid_Gard_Nodus_Small.stl.  May need to drill out to ensure a clean & circular opening.

Update (24-10-25):   (Optional) The teeth on the main dial gear were realigned to better register with the noon mark. The original design was off by 1.25 degrees.  Note that this has no impact on the reading accuracy of the dial itself since that is primarily determined by the alignment/calibration of the minute dial.  The new file is named: main_hour_dial_gear_full_v2.stl

Update (06-08-26):  (Optional) Added a secondary gear to the pedestal/latitude dial section to provide a smoother ride. Replace the lower bushing facing the latitude dial teeth with this part instead: i.e., secondary_latitude_gear.stl.  Also, the pedestal halves were slightly improved to provide a smoother ride of the latitude crescent within the pedestal.  The new parts are:   pedestal_half_A_v3_assembly.3mf, pedestal_half_A_v3.stl, pedestal_half_A_v3_logo.stl, pedestal_half_B_v3.stl.  

Update (07-08-26):  (Optional) There is an improved magnetic pedestal base/feet design available which uses larger magnets for better adhesion: https://www.printables.com/model/1802944-improved-magnetic-base-design-for-sundial-pedestal

Update (12-08-26): (Optional) The 100% printable Analemma plate requires no painting to highlight the curve but comes in multiple parts, which require assembly.  An optional design can be printed as one part but requires painting to highlight the curve.  This version also offers a thinner curve that can improve sun-alignment accuracy.  Look for: clock_hybrid_gard_-thinner_lines_curved-analemma-plate.stl

Update (14-08-26): Added assembly instructions in the file section.  Look for:  Assembly_Instructions_for_the_Solar_Measuring_Instrument_v1.0.pdf

Update (24-09-26): Many thanks go out to Chris Lusby Taylor of the British Sundial Society for his excellent suggestions on how to improve the existing design! 

List of changes:

1. Removed the equinox & solstice triangles from the original analemma plate.  Instead, thin lines were added to indicate when EoT=0 & solar declination = 0 on the analemma curve;

2. A proper CO-LAT (co-latitude) dial with a viewport was added on the opposite side of the LAT (latitude) crescent dial.  The CO-LAT is the proper way of measuring the height of the sun over the horizon vs. LAT.  The crescent is now broken into 3 parts: CO-LAT dial, LAT dial & a CO-LAT/LAT crescent gear.  This improves the labeling/text print quality & resolution by enabling both sides to be placed against the printer bed.  It also helps tighten the dimensional tolerances on the crescent gear without needing print supports;

3. The pedestal & CO-LAT/ LAT crescent adjustment mechanism was improved for sturdiness, including providing a smoother & more accurate movement.  The original design exhibited a 1-degree tilting error & the movement adjustments were a little jerky;

4. A 0 to 360 degree AZ (azimuth) dial was added to the horizontal platform to facilitate solar position measurements.  The horizontal platform is also now split into 3 parts to improve labelling/text print quality & resolution;

5. Updated assembly & operation instructions.

Replacement & new files are:

• clock_hybrid_gard_thinner_lines_curved-analemma-plate_v2.stl (optional)

• latitude_sun_gear_v2.stl

• latitude_crescent_gear.stl

• co-latitude_dial_assembly_v2.3mf

• co-latitude_dial_v2.stl

• co-latitude_dial_text_v2.stl

• latitude_dial_assembly_v2.3mf

• latitude_dial_v2.stl

• latitude_dial_text_v2.stl

• horizontal_dial_assembly_v3.3mf

• horizontal_dial_v3.stl

• horizontal_dial_text_v3.stl

• az_dial_assembly_v2.3mf

• az_dial_v2.stl

• az_dial_text_v2.stl

• pedestal_half_A_v5.stl

• pedestal_half_B_v5.stl

• pedestal_base.stl

• Assembly Instructions for the Solar Measuring Instrument v1.1.pdf

• Setup_Adjustments_&_Time_Measurements_v3.pdf

Main Features

• Accurately measures the sun's position in the sky from any location in the northern hemisphere & over all seasons;

• Accurately displays time when used as a heliochronometer;

• Fully adjustable measurements by means of rotatable knobs: i.e.

  • ±80° latitude & co-latitude, declination, or tilt angle (from zenith or horizon) to measure the sun's elevation, or to set up celestial equator alignment for the heliochronometer;

  • ±26.25° (±105 minutes) longitude/meridian-offset for translating solar mean time to local standard time, in addition to accommodating for daylight saving time;

  • 0-360° in azimuth to measure the sun's azimuth heading, or to compensate for magnetic north during true-north heliochronometer alignment; 

  • 0-360° in right ascension to measure the sun's position along the ecliptic;

  • 0-23.5° in declination to compensate for variations in the sun's elevation with respect to the celestial equator throughout the solar year;

  • ±7.5° level adjustment with 3x large screws with magnetic bottoms to help secure the base to ferrous metal surfaces;

• When used as a heliochronometer, a visual-mechanical computer called an Analemma corrects the true, or apparent, solar time to solar mean time, which is then further corrected to read actual Local Standard Time;

• Rotating the time knob moves the entire Alidade, Nodus & Analemma vertical arm assembly via a series of gears, enabling the precise positioning of the sun's shadow against a specific target point. The sun's position, or time, can then be read from the declination & right-ascension dials, or the main hour & minute dials, respectively;

• A tilt-adjustable nodus provides compensation for the sun's variation in elevation throughout the year. This feature enables a sharper shadow to be cast against the target plate, especially at elevation extremes;

• 100% printable Analemma plate requiring no painting to highlight the curve;

• Assembly measures 180 x 200 x 200 mm (W x L x H) & weighs approx. 475 grams in PETG;

• Larger magnetic feet are available at: https://www.printables.com/model/1802944-improved-magnetic-base-design-for-sundial-pedestal

• Also, if you want to place a motto on the instrument, check out my other printable at: https://www.printables.com/model/1442243-sundial-mottos

                        Northern Hemisphere design that uses a 24-hour main dial & two planetary gears

Specifications

Measurement Accuracies

• Solar Position:  ±0.5° degrees in both declination & azimuth;

• Time:  ±0.5 minutes throughout the entire solar year.  In practical terms, however, the accuracy will always be determined by the quality of its construction, assembly, and precision of its final alignment. Note that the proper time is displayed when the right ascension & declination are adjusted such that the nodus sun spot is projected onto the corresponding month/date on the analemma curve.

Dial Ranges & Tick Mark Resolutions

Mechanicals

All gears are designed for 1 tooth/mm pitch diameter.

1. Main hour dial ring gear:  

   • 144 inner teeth;

2. Secondary minute dial planetary gears (x2): 

   • 69 teeth;

3. Sun gear coupled to main hour dial ring gear, minute dial planetary gears & time adjustment knob:

   • 6 outer teeth;

4. Horizontal dial ring gear:

   • 120 inner teeth;

5. Sun gear coupled to horizontal dial ring gear & adjustment knob on horizontal dial:

   • 6 outer teeth;

6. Latitude dial ring gear:

   • 100 outer teeth;

7. Sun gear coupled to latitude dial ring gear & adjustment knob on latitude dial:

   • 6 outer teeth;

8. Longitude/meridian offset ring gear:

   • 30 outer teeth;

9. Sun gear coupled to longitude/meridian offset ring gear & adjustment knob on longitude dial:

   • 6 outer teeth.

Additional Notes

The Analemma curve was calculated, designed & plotted on a spherical surface using instructions from one of my other Printables designs, which uses several Python scripts within Blender.  Check out How a Curved Analemma Plate was Designed into this Heliochronometer from:  Curved Analemma Plate for a Heliochronometer Sundial by yba2cuo3 | Download free STL model | Printables.com

The instrument was constructed out of PETG for permanent outdoor installations.  MMU/AMS printers are not required to print in multi-color if the included 3mf files are used to simplify the construction process or to make any print modifications.

Note: The dials & crescents have two print options:

1. For dual-color parts like the dials & crescents, use the 3MF files.  They superimpose the main dials/crescents with text as separate STL files so that different print colors can be assigned;

2. If you prefer just having engraved text, use the main parts without superimposing the separate text;

3. Infill: 15-20% is sufficient, except for the alidade arm, cam follower & spring, which should be at 100% for added strength & durability;

4. Layer Height:  0.20mm is recommended;

5. Infill:  Grid pattern;

6. Material:  PETG.  For added outdoor protection, consider applying a transparent UV-resistant paint over the printed parts.  If you are experiencing delamination, too much stringing, or blobs on your prints, then try using the following settings on your printer:

Setup & Adjustments

Please refer to the instructions in the file section: i.e.  Setup_Adjustments_&_Time_Measurements_v3.pdf

To measure the Sun’s position

With the instrument base perfectly level, align it such that an azimuth reading of 180 degrees is pointing due south:

Without moving the base, rotate the alidade using the knob located under the main dial carrier & set the alidade pointer to XII (12 noon) on the main dial & 00 minutes on the minute dial pointer, as indicated below:

Now turn the co-latitude (elevation) dial knobs & the azimuth (heading) dial knobs so that the sun beam projected from the nodus pinhole is aligned with the dark spot located near the center of the analemma plate; i.e., located at the bottom of the upper teardrop shape (see photo below). That spot marks the center of an analemma spherical surface, which also happens to be at the same height & perfectly aligned with the nodus pinhole opening situated at the opposite end of the alidade. Make sure to also tilt the nodus to give the sharpest & roundest sun image projection. The instrument will provide readings of the sun’s elevation above the horizon (co-latitude) & azimuth heading for that particular time of day.  If one plots the position of the sun at the same time every day, for example at noon, over the course of a year, it will produce an analemma curve.  Alternatively, one can also plot the sun's position at every hour on sunny days (& across the months) to observe variations in the sun's motion.

The above images illustrate how the surface of the analemma plate design follows a spherical profile with the nodus opening situated at the center of the sphere.

To Read the Time

Please refer to the attached documentation for detailed instructions:  Setup_Adjustments_&_Time_Measurements_v3.pdf

With the instrument properly aligned north-south & perfectly level, & with the latitude dial of the instrument set to your own position latitude, & the longitude dial correctly set to your time meridian offset (& don't forget to add an extra hour if you are on daylight saving), tilt the nodus to give the sharpest & roundest sun image projected on the analemma plate, then adjust the time knob so that the sun is projected onto the dark analemma curve corresponding to the correct month of the year.  The instrument will provide time readings, corrected for any error contributions due to the Equation of Time (EoT).

                                      The analemma curve shown above is for the northern hemisphere.

Thank you for your interest!