Heliodon 4.0

August 10, 2009 / no comments

In an era when computer speed and software capabilities are constantly improving, one might wonder why any lighting design firm would bother with physical model-testing for daylight analysis anymore. There are many different types of software available today that can be useful for studying daylight in architectural spaces, but there are still compelling reasons why studies performed by traditional methods will never be completely replaced by computers.

The cornerstone of these methods is a multi-axis device known as a heliodon. A scale model is first secured to the table, oriented correctly north-to-south, and then the table is angled to match the latitude of the real building’s location on earth. A solar sundial is positioned next to the model to identify time of day and time of year.

Rotating and locking one axis of rotation then establishes time of year, while rotating the angled table recreates the changing time of day. Once these variables are set, one can immediately see daylight interacting accurately with the model any time of day, any time of year, anywhere on earth.

The newest heliodon at Lam Partners is a testament to the belief that physical model-testing continues to be indispensable in evaluating daylight. Easy video integration, fast modifications to the model, perfect rendering of materials, and a comprehensible interface are all reasons why we decided that upgrading our heliodon was worthwhile, and this fourth-generation model incorporates new design features gleaned from 35 years of daylight analysis experience.


The primary feature is the motorized table that allows for precise rotation, used in conjunction with a digital video camera. A heliodon is able to quickly cycle through sunrise to sunset, so smooth rotation at a consistent speed is critical for high-quality video output.

Another feature is a wide, stable, and adjustable base platform that is removable and can be field-leveled for the most accurate results. Part of the overall design objective was to make the entire heliodon easily broken down and portable, with three easily reassembled components that all use the same size bolt. All necessary tools are stored neatly within the frame and easily accessed.


The improved precision of the new heliodon required a sundial that was equally precise. We designed a new one and had it CNC machined from solid aluminum, like the heliodon (yes, the chips were all recycled!). The new construction features an adjustable and lockable latitude angle, as well as a removable and replaceable gnomon that can be safely stored within to prevent damage. A polar sundial design was then laser-etched onto the front for durability.

Together, the new heliodon and sundial provide a level of exactitude never before realized in earlier designs. After the initial set-up, an architectural model can easily run through an entire year’s worth of sun-angles in barely an hour on the heliodon. Since sunlight works the same at any scale, measured footcandle levels inside the model, when factored to account for local latitude and season, are accurate and reliable.

This breadth of valuable information takes far longer to gather using computer software which usually lacks the intuitive feel and quick adjustments that physical modeling offers, and most daylighting software continues to struggle in accurately representing complex materials and textures or multiple reflections.

So, while Lam Partners certainly does use software for some aspects of daylight study such as basic sun-angle geometry, the qualitative advantages inherent to heliodon analysis make it an extremely useful tool for daylight-intensive projects.


Photo Credits: Anna Baranczak / Lam Partners Inc (1, 4), Justin Brown / Lam Partners Inc (2, 3)