---
title: "Cover Glass Spherical Aberration calculator — AperiOptic"
description: "Primary spherical aberration of a cover-glass thickness error, dry objective (NA in air), third order. Free online optics calculator, with the formula and code snippets."
url: "https://aperioptic.com/calculators/cover-glass-spherical-aberration"
---

# Cover Glass Spherical Aberration calculator

Primary spherical aberration of a cover-glass thickness error, dry objective (NA in air), third order.

Category: [Aberrations](https://aperioptic.com/calculators)

Formula: `WSA ≈ (n²−1)/(8n³) · NA⁴ · Δt`

## Inputs

| Input | Parameter | Unit | Default |
| --- | --- | --- | --- |
| Index n | `n` |  | 1.515 |
| NA (air) | `NA` |  | 0.95 |
| Δ thickness | `dt` | µm | 10 |
| λ | `lam` | nm | 550 |

## Result with the default inputs

- Wavefront error: 379.2379 nm
- In waves: 0.6895

Open it with your own values: put each input in the address as a parameter, for example [`/calculators/cover-glass-spherical-aberration?n=1.515`](https://aperioptic.com/calculators/cover-glass-spherical-aberration?n=1.515). A unit other than the listed one goes in `<parameter>_unit`.

Read more: [Wikipedia: Spherical aberration](https://en.wikipedia.org/wiki/Spherical_aberration)

[All optics calculators](https://aperioptic.com/calculators)

---

The interactive page: https://aperioptic.com/calculators/cover-glass-spherical-aberration (AperiOptic runs in the browser; free, no account). Every page of the site as Markdown: https://aperioptic.com/llms.txt