> ## Documentation Index
> Fetch the complete documentation index at: https://docs.getbased.health/llms.txt
> Use this file to discover all available pages before exploring further.

# Log sun exposure sessions in getbased

> Record sun sessions, model wavelength-related light signals, and keep timing and skin-safety context together.

The **Light** lens records where, when, and how sunlight reached you. getbased uses weather data and a browser-side spectrum model to describe six wavelength-related signals. These are modeled inputs, not measured biological responses, diagnoses, or daily requirements.

## What the six channels mean

| Channel | What the log represents | Important limit |
| - | - | - |
| **Vitamin D** | Vitamin-D-effective UVB modeled at uncovered skin | It does not measure vitamin D synthesis or blood status, and an empty log is not a deficiency |
| **Skin & mood** | UV-related POMC pathway input at skin | It does not measure hormones, mood, or an outcome |
| **Blood vessels** | UVA-related skin input associated with nitric-oxide release | It is not a blood-pressure reading or a reason to seek more UVA |
| **Outdoor eye light** | Violet/cyan outdoor light reaching the eye under the logged conditions | Human pathway details remain exploratory; never look at the sun |
| **Body clock** | Timed ambient light reaching the eye | Timing matters more than a score; ordinary ambient outdoor light is sufficient to log this signal |
| **Cell energy & repair** | Red and near-infrared light modeled at skin and deeper tissue | Systemic effects remain under study and are not measured by the app |

Two additional red and near-infrared channels are used for compatible light-device sessions. Device output stays distinct from full-spectrum sunlight in the UI and AI context.

The channel detail cards show the source of a logged signal, its seven-day rhythm, and plain-language context. They do not show progress toward a universal daily target. No matching exposure means only that none was recorded.

## Log a session

<Steps>
  <Step title="Start a session">
    Choose **Log a sun session** in the Light lens or **Light Today** dashboard widget. getbased fetches the available atmosphere snapshot for your rounded location and starts accumulating the modeled signal.
  </Step>

  <Step title="Adjust details when needed">
    Use the full picker to record exposed body regions, eyewear or window conditions, and SPF. The quick log reuses the previous session's choices.
  </Step>

  <Step title="Stop the session">
    Choose **Stop session** when you finish. Review the recorded duration, conditions, safety estimate, and channel signals.
  </Step>
</Steps>

### First-time setup

The setup records context used by the model:

* **Fitzpatrick skin type** provides a rough reference for the erythemal model; it is not a personal safe-time guarantee.
* **Home lighting** and the optional 10-question indoor-light audit add screening context.
* **Eyewear outside** changes the estimated spectrum reaching the eye.
* **Location precision** starts from the country in your profile. Precise location is optional, stays device-local, and is not synced.
* **Photosensitizing medication** records a caution. getbased does not apply a universal multiplier because the medicine, dose, formulation, and reaction type matter.

<Warning>
  Medication photosensitivity and the app's burn estimate cannot establish a safe exposure time. Follow the medication guidance and ask the prescribing clinician or pharmacist when unsure.
</Warning>

## Controls during a session

| Control | What it does |
| - | - |
| **Pause** | Stops signal accumulation during a shade or indoor break while retaining the overall session timeline |
| **Flip** | Records that you changed orientation; it does not multiply dose or assume that more skin became exposed |
| **Body regions** | Update these if the uncovered area changes after turning or covering up |
| **Sunscreen** | Commits the previous interval and continues with the newly selected SPF context |
| **Ozone override** | Records a total-column ozone value when you have a trustworthy source |

The detailed picker includes front and back body regions. A flip by itself does not change the chosen coverage, so update the regions whenever coverage changes.

## Skin-safety estimate

getbased computes a CIE-erythemal-weighted Standard Erythemal Dose and compares the cumulative daily result with a Fitzpatrick reference MED. The UI uses qualitative caution states as the modeled fraction rises.

This is an estimate built from atmospheric inputs and logged coverage. It does not account for every personal, medication, reflection, altitude, or skin-condition factor and must not be treated as a guarantee against burning. A photosensitivity flag increases the caution shown without inventing a numeric threshold adjustment.

## Sun data sources and location privacy

Choose a source in the Light lens:

| Source | Behavior |
| - | - |
| **Auto** | Uses a configured self-hosted source when present; otherwise the official app requests CAMS context through the dedicated compatibility relay, then falls back to browser-direct Open-Meteo |
| **Open-Meteo** | Contacts Open-Meteo directly from the browser |
| **Self-hosted** | Contacts the compatible public HTTPS endpoint you configure; if it fails validation or is unavailable, the app falls back to Open-Meteo |

Older stored CAMS, NOAA, or manual modes migrate to **Auto**. Manual source selection is no longer offered in the current UI.

On the official app, latitude and longitude are rounded to 0.1°—roughly an 11 km grid—before either the CAMS request or Open-Meteo fallback. The CAMS compatibility service reads its local atmosphere grid and does not forward those coordinates to Copernicus or Open-Meteo. If fallback is needed, the browser sends the same rounded location directly to Open-Meteo. The static application host does not receive these weather requests. A self-hoster can choose its own compatible service and rounding policy.

Source confidence reflects observable uncertainty such as snapshot age, cloud cover, sun elevation, source coverage, and stale data. It is not instrument accuracy.

## Light devices

You can add a therapy panel, SAD lamp, dawn simulator, or other device with stated or measured wavelength and irradiance information. Presets and custom devices map their output to the relevant signals. A device session never stands in for sunlight, and a manufacturer specification is not an independent measurement.

## AI interpretation and context

You can request an AI interpretation from a completed session. The app supplies the logged conditions, modeled signals, uncertainties, device use, and safety context. The AI is instructed not to infer vitamin D status, call a channel deficient or complete, recommend looking at the sun, or turn a missing log into a medical conclusion.

<Info>
  Read the complete [Sun-session instruction](/developers/system-prompts-light#prompt-light-sun-session) or [light-device-session instruction](/developers/system-prompts-light#prompt-light-device-session) to see exactly what the AI is asked to explain and avoid.
</Info>

Sun sessions, light-device sessions, and indoor-light records belong to **Insight → Manage → Context → Data sources → Light & Sun context**. With that source enabled, chat can receive recent source and rhythm summaries, safety cautions, configured devices, and indoor screening context. Turning it off does not delete the records.

When relevant Genome markers are available, getbased may add conservative association context to the modeled vitamin D response. It does not calculate a personal vitamin D dose or replace a 25-OH vitamin D test.


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