Solar Motion, Position & Time Measurement Instrument - Southern Hemisphere

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

Please note that all photos shown here are the northern-hemisphere version!

The northern & southern versions of this heliochronometer share the same design, except for the following parts which require substitution & are provided in the file section; i.e.

• Analemma:  Rotated curve & months by 180deg.

• Minute Dial:  Mirrored;

• Hour Dial:  Mirrored.

The balance of the parts need to be downloaded from here:  Solar Motion, Position & Time Measurement Instrument - Northern Hemisphere by 3DMason | Download STL model | Printables.com

There is also an optional improvement for the magnetic pedestal base design available here: https://www.printables.com/model/1802944-improved-magnetic-base-design-for-sundial-pedestal

Main Features

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

• Accurately displays time when used as a heliochronometer;

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

  • ±80° latitude, declination, or tilt angle (from zenith) to measure the sun's elevation, or for celestial equator alignment of the heliochronometer;

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

  • 0-360° in azimuth to measure the sun's 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 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 post-processing; i.e., no painting required 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 with a 24-hour main dial and 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 on the analemma curve.

Dial Ranges & Tick Mark Resolutions

Mechanicals

1. Main hour dial ring gear:

   • 144 inner teeth;

   • 144mm pitch dia.

2. Secondary minute dial planetary gears (x2): 

   • 69 teeth;

   • 69mm pitch dia.

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

   • 6 outer teeth;

   • 6mm pitch dia.

4. Horizontal dial ring gear:

   • 120 inner teeth;

   • 120mm pitch dia.

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

   • 6 outer teeth;

   • 6mm pitch dia.

6. Latitude dial ring gear:

   • 100 outer teeth;

   • 100mm pitch dia.

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

   • 6 outer teeth;

   • 6mm pitch dia.

8. Longitude/meridian offset ring gear:

   • 30 outer teeth;

   • 30mm pitch dia.

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

   • 6 outer teeth;

   • 6mm pitch dia.

Additional Notes

The Analemma curve was calculated, designed & plotted on a spherical surface using instructions from one of my other Printables, which uses several Python scripts in 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 & to make any print modifications.

Note: The dials & crescents have two print options: i.e.

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 such that different print colors can be assigned;

2. If you prefer engraved parts only, just use the main parts without 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, or 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 top of the lower 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 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).

Thank you for your interest!