This design was inspired by the Aten Heliochronometer Sundial, model B4003, designed and built in the 1990’s by the craftsman J.D. Gard of Tucson Arizona. It’s a beautiful instrument made out of brass and aluminum and it claimed an accuracy to within 1 minute. Unfortunately, only a few were built and they are a relatively rare find today. The instrument was adjustable for latitude and longitude and corrected for the equation of time; i.e. Analemma, for accurate time telling in any time zone. It originally measured about 26cm high and 30 cm across but this model is slightly scaled down to facilitate printing.

This design can be used in either northern or southern hemispheres.

• Accurate to within 1 minute throughout the entire solar year from any location in the northern hemisphere. In practical terms, however, the accuracy will be determined by the quality of its construction, assembly and precision of its final alignment;
• UPDATE (12-26-24): Now supports southern hemisphere!
• 5 minute reading resolution on the main dial plate;
• 0 to 5 minutes reading resolution on a large, easy to read, secondary Vernier scale, in increments of 30 seconds;
• Main dial plate was reduced to a ring, similar to those found on equatorial sundials, with the purpose of reducing material & print time without sacrificing accuracy or sturdiness;
• 1 degree latitude adjustment resolution;
• Improved construction, using minimum number of parts and a simplified but reinforced latitude adjustment protractor arm;
• Replaceable Nodus cone with small circular sight for improved reading resolution, or adopt your own custom design!;
• Displays Local Mean solar time directly by computing corrections to the true, or apparent solar time. It achieves this by utilizing a visual-mechanical computer, also known as an analemma plate;
• Converts Local Mean Time to Standard Local Time via meridian dial offset adjustments;
• Please note that this version of sundial does not directly compensate for daylight savings time. You will need to do a mental conversion;
• 4 base design options are available; 3 with integrated magnetic compass and levels, and 1 without. For compass/level options, refer to these printable links:
• Tri-leg: https://www.printables.com/model/1012539-improved-heliochronometer-sundial-base-design-with
• Leveling base & tripod head: https://www.printables.com/model/1012575-heliochronometer-sundial-mount-for-head-leveling-b
• Assembly measures 180x200x200mm (W x L x H).

The prototype was constructed out of ABS but I would highly recommend that you use Polymaker HT PLA or HT PLA GF for sun & heat resistance!

Curved vs. Flat Analemma Plates:
This model includes a flat plate analemma & fixed nodus. You may gain a bit more performance & reading accuracy from your heliochronometer if you adopt a curved plate design with a tilt adjustable nodus. If you prefer to swap these out, check out my other designs at:
Northern-Hemisphere:
https://www.thingiverse.com/thing:6923731
https://www.thingiverse.com/thing:6887037
Southern Hemisphere:
https://www.printables.com/model/1156836-curved-analemma-plate-design-for-southern-hemisphe
https://www.printables.com/model/1080230-new-larger-curved-analemma-plate-with-tiltable-nod

Planetary Geared Sundial & Clock Hybrid - with Reading Accuracy Optimization:
Also, if you find Vernier scales difficult to read, check out my other Geared Heliochronometer Sundial designs which utilizes a novel Secondary Minute Dial:

https://www.thingiverse.com/thing:6859170
https://www.thingiverse.com/thing:7002663

The analemma curve was calculated & plotted using MS Excel and then scaled to match the size (diameter) of this heliochronometer.

Update (12-07-24): If you live in the southern hemisphere, make sure to use the southern hemisphere analemma design in addition to the southern hemisphere dial plate.

For instructions on how to assemble, align & use, refer to the included instructions in the file section.

If you think this is a cool design, don't forget to hit the like button. I hope you enjoy building this design & thanks for your support!

• Printer brand: Prusa
• Model: i3 MK4S
• Supports: Yes, on parts flagged by your slicer program
• Resolution: 0.15mm OPTIMAL
• Infill: 20%
• Brim: Yes - 10 to 20mm
• Filament brand: Doesn't matter
• Filament material: Recommend Polymaker HT PLA for heat & sun resistance
• Filament color: Doesn't matter but pick two contrasting colors
• Special Notes:
  • Print in an enclosure for best results.
  • Use a darker color filament at a specific layer height to highlight the text if you have a single extruder or an MMU
  • Slow printer speed to 75% on top layers will improve tick mark production.

Construction
The construction of this sundial is relatively simple, making use of M3 & M4 hardware. A list of assembly material is provided below, along with where it's used. Also check the description associated with each file for more assembly details. All parts can be easily disassembled and reassembled to facilitate transportation.

All HW is Stainless Steel Button Head Hex Socket Head Cap Screws and Nuts, unless specified otherwise.

Qty Description - Where Used
4 M4x15mm screw - Dial holder to dial ring; (fixes dial holder to dial ring)
1 M3x10mm screw - Pivot screw for Vernier Scale; (attaches to Alidade)
1 M3 square nut - For above
1 M3 Washer - For above
3 M4x16mm screw - Pedestal to protractor
3 M4 nuts - Used with above
3 M4x30mm screw - For base leveling. Screws in at ends of base
6 M4 nuts - Locks base levelling screws (top and bottom) once level.
1 M4x20mm screw - For Alidade (horizontal arm) pivot
1 M4 Nyloc nut - For above (Alidade pivot)
1 M4 flat washer - For above (Alidade pivot)
2 M4x20mm screw - Top screws for securing dial ring to protractor
1 M3x35mm screw - Bottom screw for securing dial ring to protractor
4 M4x20mm screw - (2x) attaches Pedestal to base. - (2x) attaches Nodus and Analemma vertical arms to Alidade (horizontal arm).

• Deburring tool for removing excess plastic from printed parts
• Hand Drill or Drill Press
• 2.5mm or 7/64" drill bit for enlarging holes for M3 tap
• 3.3mm or 1/8" drill bit for enlarging holes for M4 tap
• M4 tap for making threads

• Magnetic Compass
• Circular Bubble Level
• Alternatives: Smart phone with: 1) Compass or GPS app, 2) level app.

Can't stress enough the importance of having a well aligned heliochronometer in order to make accurate and consistent readings.

UPDATE (01-02-25): As requested, please follow the new set of detailed setup & use instructions provided in the file section.

Also, refer to the additional information available here: https://www.printables.com/model/1027109-gard-heliochronometer-sundial-derivative

1. Sundials - Their Construction & Use, R. Newton Mayall & Margaret Mayall, Dover Publications Inc., 1994
2. The Equation of Time: https://equation-of-time.info/work
3. https://www.printables.com/model/998688-heliochronometer-worlds-most-accurate-sundial
4. https://www.printables.com/model/1019930-heliochronometer-version-2-worlds-most-accurate-su
5. https://www.printables.com/model/1036568-curved-analemma-plate-for-a-heliochronometer-sundi
6. https://www.printables.com/model/1080230-new-larger-curved-analemma-plate-with-tiltable-nod