Sun Path: Letterkenny, Ireland

Direct answer

For Letterkenny at 54.9500, -7.7333, the declination-only solar-noon altitude is approximately 58.5° at the June solstice, 35.0° at an equinox and 11.6° at the December solstice. Refine these geometry checks with the project date, civil time, facade azimuth, terrain and local horizon. The reproducible location record is GeoNames ID 2962961 in administrative area U, at 54.9500, -7.7333; replace it with the surveyed parcel point before relying on the result. As a transparent geometry check, declination-only solar-noon altitude is about 58.5° at the June solstice, 35.0° at an equinox and 11.6° at the December solstice. Representative 21st-day geometry ranges from about 6.9 hours in December to 17.1 hours in June; this excludes atmospheric refraction, terrain and obstruction effects. The cited national authority is a discovery starting point; current local documents and a named qualified reviewer control project use of this sun path record.

Prepared by Harth · Prepared from the cited location and country sources; local project inputs remain unreviewed · Published 2026-08-26 · Updated 2026-08-31.

What must be verified for Letterkenny?

Letterkenny is represented here at approximately 54.9500, -7.7333 for discovery and workflow planning. A project address, parcel, elevation, exposure, authority, and submission date must replace that city-centre reference before design use.

How should sun path be established?

1. Fix the surveyed site and local time basis.
2. Select an authoritative weather source or a named solar-position algorithm.
3. Record period, percentile or scenario and units.
4. Test sensitivity to elevation, exposure, urban form and horizon.
5. Save the source file, retrieval date and checker in the model record.

What are the limits of this worksheet?

This sun-path-workflow page is a project-starting worksheet, not a design value or approval. The controlling authority and qualified professionals for the Letterkenny site remain authoritative.

Which related searches does this primary location record cover?

This primary route consolidates the location evidence needed for Sun Path, Solar Altitude & Azimuth, Solar Shading Design, Daylight & Orientation. A narrower route should be released only when it adds a materially different official source, calculation, process, threshold or worked example.

Letterkenny monthly solar geometry check for sun path

Month-by-month geometry interpretation

• 21 January: approximate solar-noon altitude 14.9° (zenith angle 75.1°) and 7.8 hours of geometric daylight. That is 0.9 hours longer than the preceding representative date in this annual sequence.
• 21 February: approximate solar-noon altitude 23.8° (zenith angle 66.2°) and 9.8 hours of geometric daylight. That is 2.0 hours longer than the preceding representative date in this annual sequence.
• 21 March: approximate solar-noon altitude 34.6° (zenith angle 55.4°) and 11.9 hours of geometric daylight. That is 2.1 hours longer than the preceding representative date in this annual sequence.
• 21 April: approximate solar-noon altitude 46.6° (zenith angle 43.4°) and 14.3 hours of geometric daylight. That is 2.3 hours longer than the preceding representative date in this annual sequence.
• 21 May: approximate solar-noon altitude 55.2° (zenith angle 34.8°) and 16.2 hours of geometric daylight. That is 1.9 hours longer than the preceding representative date in this annual sequence.
• 21 June: approximate solar-noon altitude 58.5° (zenith angle 31.5°) and 17.1 hours of geometric daylight. That is 0.9 hours longer than the preceding representative date in this annual sequence.
• 21 July: approximate solar-noon altitude 55.5° (zenith angle 34.5°) and 16.3 hours of geometric daylight. That is 0.8 hours shorter than the preceding representative date in this annual sequence.
• 21 August: approximate solar-noon altitude 46.8° (zenith angle 43.2°) and 14.3 hours of geometric daylight. That is 2.0 hours shorter than the preceding representative date in this annual sequence.
• 21 September: approximate solar-noon altitude 34.8° (zenith angle 55.2°) and 12.0 hours of geometric daylight. That is 2.3 hours shorter than the preceding representative date in this annual sequence.
• 21 October: approximate solar-noon altitude 23.3° (zenith angle 66.7°) and 9.7 hours of geometric daylight. That is 2.3 hours shorter than the preceding representative date in this annual sequence.
• 21 November: approximate solar-noon altitude 14.6° (zenith angle 75.4°) and 7.7 hours of geometric daylight. That is 2.0 hours shorter than the preceding representative date in this annual sequence.
• 21 December: approximate solar-noon altitude 11.6° (zenith angle 78.4°) and 6.9 hours of geometric daylight. That is 0.8 hours shorter than the preceding representative date in this annual sequence.

Harth calculation for latitude 54.9500°: Cooper declination approximation, 90° - |latitude - declination| at solar noon, and centre-to-centre sunrise hour angle. See NOAA's solar calculation details for fuller method context. This screening table excludes equation-of-time/civil-time conversion, atmospheric refraction, terrain, facade azimuth and obstructions; it is not an hourly shading result.

Where can you explore related guidance?

• Explore all solar data guidance
• Sun Path: Sligo, Ireland
• Sun Path: An Muileann gCearr, Ireland
• Sun Path: Athlone, Ireland
• Sun Path: Dundalk, Ireland

Sources and method

Location data from the GeoNames IE dump (CC BY 4.0, snapshot 2026-08-31, GeoNames ID 2962961). Regulatory starting point: Department of Housing, Local Government and Heritage and the local building-control authority. Figures are illustrative — verify against the current locally adopted edition for the site. Solar-method context: NOAA Solar Calculation Details; the Harth monthly table uses a simpler declination and geometric-daylight approximation whose stated limitations must be retained.

Source links

• download.geonames.org

• gov.ie

• gml.noaa.gov