Source: https://guthlabs.ai/docs/instruments/telescope-f-ratio/implementation/

instrument implementation / implementation-contract

# Telescope f-ratio implementation

A source-bound implementation contract for Telescope f-ratio; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t2-041

**Effect**: Computation or source lookup only

## Input and validation requirements

The zero-aperture input produces an undefined f-ratio and should be rejected. The specification also leaves unit normalization unspecified, allowing a 1 m versus 100 mm input to be incorrectly computed as f/0.01 instead of f/10.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "focal_length": 100,
    "focal_length_unit": "mm",
    "aperture_diameter": 50,
    "aperture_unit": "mm"
  },
  "expected_outputs": {
    "f_ratio": 2,
    "relative_speed_vs_f10": 25
  },
  "working": "f_ratio = 100 mm / 50 mm = 2. relative_speed_vs_f10 = (10 / 2)^2 = 5^2 = 25."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/telescope-f-ratio/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/telescope-f-ratio/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/telescope-f-ratio/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche2/tranche2-results.json`