Super Accurate Heliochronometer Sundial - 2025 - Accurate to within 1 minute!
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A beautiful & Super Accurate Heliochronometer type sundial that you can set your watch to.
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- 5 / 5
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- 2
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Informacje o modelu
- Źródło
- Printables
- Kategoria
- Outdoor & Garden
- Licencja
- Creative Commons — Attribution — Noncommercial — Share Alike
A remix of this model is available with added improvements & features. Check out: https://www.printables.com/model/1486576-heliochronometer-sundial-2026
A great deal of effort has gone into this design, so please consider leaving a like or comment—it would mean a great deal to me. And if you have any feedback, I’d love to hear it!
This sundial leverages the design features from two of my other sundials:
This design is specific to the northern hemisphere. If you live in the southern hemisphere, refer to this design instead: Super Accurate Heliochronometer Sundial - 2025 - Southern Hemisphere Version by 3DMason | Download free STL model | Printables.com
The northern & southern versions of this heliochronometer share the same design, except for the following parts, which require substitution; i.e.
Analemma: Curve rotated by 180 degrees on the vertical arm;
Minute Dial: Mirrored;
Hour Dial: Mirrored.
Change History
Update (1-12-25): (Optional Improvement) Alignment marks were added to both sun & planetary gears to facilitate assembly. The updated parts are listed as clock_hybrid_gard_sun_gear_v3.stl & clock_hybrid_gard_planetary_gear_v2.stl
Update (14-11-25): (Optional Improvement) 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 & precise opening.
Update (28-10-25): (Optional Improvement) A printer-friendly analemma curve that doesn't require any messy post-processing/painting to highlight the curve. Check out: Print Friendly Curved Analemma Vertical Plate for 3DMason Heliochronometers by 3DMason | Download free STL model | Printables.com
Update (24-10-25): (Optional Improvement) The teeth on the main dial gear were realigned to better register with the noon mark on the main hour dial. The original design was off by 1.25 degrees. Note that this has no impact on the dial's reading accuracy, since the minute dial's alignment primarily determines it. The new file is named: Clock_Hybrid_Gard_Main_Dial_Gear_v2.stl
Update (10-05-25): There was an omission of the minute pointer on the Alidade in the original design. It has since been corrected in version 2.
Update (02-06-25): Increased clearance of the alidade over the hour dial to improve riding. Parts affected are:
Clock_Hybrid_Gard_Planetary_Gear_Mount_v2 (increased height);
Clock_Hybrid_Gard_Sun_Gear_v2 (increased length);
washer_spacer (new). To be added on the opposite side of the planetary gear, above the planetary gear mount & under the minute dial. See photo below:
Alternatively, one can also add an extra planet gear instead of the washer spacer; i.e., Clock_Hybrid_Gard_Planetary_Gear.stl. Adding an extra planet gear will also reduce some unwanted backlash, depending on the quality of your build. However, you will need to use the Full Main Dial from here: Full Main Dial for 2025 Heliochronometer Sundial by 3DMason | Download free STL model | Printables.com to rotate the alidade fully.
Main Features
Time readings are accurate to within 1 minute throughout the solar year & from any location. In practical terms, however, the accuracy will always be determined by the quality of its construction, assembly, and the precision of its final alignment;
The time reading is “tuned in” by turning a knob located under the main hour dial. Rotating the knob moves the entire Alidade, Nodus & Analemma assembly via a series of gears, which enables the precise positioning of the sun's shadow against the Analemma vertical plate. The time is then read from the main hour & minute dials;
The main dial crescent has a coarse time reading resolution of 5 minutes;
The Alidade is coupled to a 0 to 60 secondary minute dial with a finer 1-minute reading resolution;
Adjustable Latitude Scale Dial with 1-degree reading resolution;
The Alidade Vernier is replaced with a planetary gear system consisting of a sun gear & a planetary gear traveling around an outer ring gear on the main dial plate;
The main dial crescent, along with the secondary minute dial, 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 curve;
It converts Local Mean Time to Standard Local Time via meridian offset dial adjustments with 5-minute resolution;
Added a time compensation feature to the main dial to adjust for Daylight Saving Time;
25% larger Analemma plot on a curved (spherical surface) vertical arm for improved reading resolution & accuracy;
A tilt-adjustable Nodus hole within a 25% larger curved vertical arm for Sun Elevation Compensation throughout the year. This feature enables a sharper shadow to be cast against the Analemma plate, especially at the elevation extremes;
The sundial reads time between 5:30 AM & 6:30 PM. This is due to the design of the crescent main dial, which limits the full rotation of the alidade & gear mechanism. If you are looking for an unrestricted time reading outside of this time range, then please refer to my main full-dial remix available here: Full Main Dial for 2025 Heliochronometer Sundial by 3DMason | Download free STL model | Printables.com
Improved resolution & print features on all dials;
4 base options are available: 3 with integrated magnetic compass and levels, and 1 without. For compass/level options, refer to these printable links:
Assembly measures 180 x 200 x 200 mm (W x L x H).
The heliochronometer prototype was constructed out of ABS, but I recommend using PETG or ASA for permanent outdoor installations. Use the included 3mf files to simplify the construction process or to make any print adjustments. Coating the parts with a transparent UV-protective paint can also extend the life of your sundial or prevent discoloration.
How was it designed?
A: Sundial Specifics
For definitions on the various parts that make up a heliochronometer sundial & how they work, see my other Printable at: Heliochronometer - World's Most Accurate Sundial by yba2cuo3 | Download free STL model | Printables.com
The spacing between the Nodus & Analemma vertical arms was increased to 100mm; i.e., 20mm greater than the original 80mm design. This spacing increase results in a 25% dimensional increase of the Analemma Curve, therefore increasing the overall reading resolution & accuracy by an equal amount.
The larger Analemma curve was calculated, designed & plotted on a spherical surface using the instructions from one of my other Printables, which utilizes 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 Nodus was modified to add a tilt feature & the original flat vertical arm was converted to a curved design. Therefore, the Nodus elevation can now be adjusted to match the sun's height above the horizon during the course of the year. This results in a sharper sun spot cast against the Analemma plate, which also helps with reading accuracy.
The mounting locations for the vertical arms on the original Alidade remain unchanged from my original heliochronometer designs, which means that the larger curved plate Nodus & Analemma designs presented here can be used on my other heliochronometer designs without any additional modifications, i.e.
Both hour & minute dials were generated using an online template design tool; i.e., Clock Face Templates - Metric + Inch. The SVG drawing was then imported into Inkscape & then modified/enhanced for Blender. Once imported into Blender, a thickness was assigned to each dial & then saved as an STL.
B: Planetary Gear Design Specifications
Common to all Gears:
Pressure Angle: 20 degrees;
Module: 1;
Backlash: 0mm;
Root Filet Radius: 0.5mm.
1 Planet Gear with Carrier:
69 teeth;
69mm Pitch Dia.
Sun Gear:
6 teeth;
6mm Pitch Dia.
Outer Crescent Gear:
94 inner teeth;
144mm Pitch Dia.
Print Settings
Printer brand: Prusa
Model: MK4S
Supports: Yes, on some of the parts which are flagged in your slicer app
Resolution: 0.2mm
Infill: 20% for most parts & 50% for the sun gear to add strength
Brim: Yes, on some of the larger parts, if you use ABS, etc.
Filament brand: Doesn't matter
Filament material: ABS, but OK to use other materials like PETG or ASA
Filament color: Doesn't matter
Special Notes:
Print in an enclosure for best results.
Dial Print Options – Deboss or Emboss Single Part vs. Multi-Part
There are a number of approaches to highlighting text on printed dials. Two print options are presented in this design: (A) Debossed or Embossed Single-Part Object; or (B) Separate 2 Part Solution.
(A) Deboss or Emboss Single Part Object:
The traditional method is to deboss (engrave), or emboss (raise) the text & numbers, etc., onto a single part and then use a slicer program to change the filament color at a specific height, either below (engrave), or above (raise) the main surface. Pros: simple & durable with no post-processing. Cons: Any (lighter color) on the main surfaces may darken due to the (darker) deboss colors “bleeding” through. However, this would not be an issue with embossing, but the embossing details can be easily knocked off.
Another option is to print the main debossed parts in one color, then to fill in the debossed details with a filler like Markal B Paintstik Paint Pencil, followed by wiping off any excess with a dry cloth, followed by a bit of Isopropyl Alcohol to remove any “staining” remaining on the main surface. Pros: Simple & Effective. Cons: Messy & not as durable outdoors. See this article for an explanation of the procedure: Labeling Your Parts with Engraver Filler;
Paint the entire top surface of the deboss area, then sand off the excess paint from the main surface. Pros: Simple & durable. Cons: Messy & labor-intensive. It may also remove some of the finer print details due to mechanical abrasion.
(B) Separate 2 Part Objects:
The best approach that I have come across is to have letters, numbers, symbols, etc., defined as separate objects and to bring them in at equal heights to the main surface, which can then be printed in different colors. Separate objects create cleaner & clearer boundaries and yield a completely flat surface. Additionally, the best print quality can be achieved if your text & features are against the print bed. If you are looking for more details, the technique is clearly described here: http://3dfaq.net/03_designing_for_3d_printing/01_multi_colour
There is also a faceplate design example using Fusion 360, which further illustrates the principle: https://www.printables.com/model/1040553-sundial-faceplate
2 Part Object Import using PrusaSlicer
If you use PrusaSlicer, there is no need to align or center the parts after importing. They will come in at the correct superimposed positions. Here is the procedure:
Import Part A (main body) 1st. The part will center on the bed;
If the text or features are not against the print bed, flip the object by 180 degrees;
Under Editing, left-click the icon next to Part A, then add part & load, then choose Part B (text & numbers). Optional: Re-center Part B over Part A. Both parts will now be aligned in the 3D viewer.
You can also then use the Multi-Material Painting feature following this guide: Multi-material painting | Prusa Knowledge Base
RECOMMENDATIONS: The easiest approach is to utilize the 3mf files included in the file section. The project files will take care of all the required settings so you can print all the multi-object parts directly without any fuss. Alternatively, if you plan to print in ABS, use the provided G-code files, or modify any of the project settings to your liking if you want to print in other materials.
Since I don't own an MMU printer, “virtual” extruders were assigned to each color in the slicer program & the filament change G-code command (M600) was issued instead of extruder changes. This is a commonly used technique that essentially tricks the printer into thinking it has multiple extruders. This technique also allows one to change filament color for different areas on the same print layer, therefore, making it possible to print all colors in one print job. Print the surface with text & graphics against the bed for best quality.
Required Assembly Hardware & Instructions
The construction of this sundial is relatively simple, making use of M2, M3 & M4 Stainless Steel Button or Cap Head Screws and Nuts. A list of assembly materials is provided along with where they're used. All parts can be easily disassembled and reassembled to facilitate transportation. See the file section for the assembly instructions: i.e., Gard_Clock_Hybrid_Assembly_Instructions_v1.
Tools For Sundial Alignment
Magnetic Compass;
Circular Bubble Level;
Alternatives: Smartphone with: 1) Compass or GPS app, 2) level app.
How to Use
Before using, make sure that:
Your sundial is perfectly level;
Your latitude is set on the latitude scale;
Your sundial is pointing to true north.
For alignment procedures, adjustments for time zone meridian offsets & daylight saving time, etc., refer to the attached file named: How_to_Setup_your_Gard_Clock_Hybrid_Sundial-Detailed-Instructions_v1.
How to Read the Time: Simply turn the dial knob located at the bottom of the main sundial plate to rotate the Alidade until the light through the Nodus hole is aligned with the dark curve portion on the vertical Analemma plate. Make sure that you are on the correct left or right portion of the Analemma curve corresponding to the current month of the year. Do not try to move the Alidade from the Nodus, or from the Analemma vertical arms, or you will end up damaging the gear system. Only use the knob to rotate the alidade/nodus/analemma assembly. The hour will be displayed on the main hour dial & the minutes on the secondary minute dial. The Alidade pointer will indicate the time to within 5 minutes & the secondary minute dial to less than 1 minute.
If there appears to be too much resistance or play in the assembly when rotating the bottom knob, try loosening or tightening the screw that holds it against its shaft. Alternatively, you can also try loosening or tightening the screw at the alidade pivot point. The correct tightness of both screws should yield a smooth & consistent operation.
References:
Gard Heliochronometer Sundial Derivative by 3DMason | Download free STL model | Printables.com
Sundials - Their Construction & Use, R. Newton Mayall & Margaret Mayall, Dover Publications Inc., 1994
The Equation of Time: The Equation of Time