[Bug] Mond Moon Illumination Fraction is jumping

[ldoench]

Short summary 📝

Moon Illumination Fraction shows stepped values/plateaus instead of continuous curve

Detailed description 📋

Description:
The moon_illumination_fraction does not update continuously. Instead of a smooth transition reflecting the astronomical reality, the values remain static for several days (forming horizontal plateaus in charts) and then jump abruptly to a new value. For example, the value jumped from approximately 95% to 66% on March 9th without any intermediate data points.

Additionally, the reported values appear to be outdated. On March 14, 2026, the sensor reported 66.10%, while the actual astronomical illumination was significantly lower (approx. 18%).

Steps to Reproduce:

Monitor the moon_illumination_fraction over a period of 48–72 hours.

Observe the state history/charting.

Compare the output value with real-time astronomical data.

Expected Behavior:
The illumination fraction should update incrementally (approx. 0.2% to 0.5% change per hour) to form a continuous, smooth curve.

Actual Behavior:
The value remains identical for long periods and then performs a vertical "jump" to a much later state, skipping all intermediate percentages.

Screenshot:

Additionally: The float value should not need this precision:

Version 📌

No response

Environment 🌐

home assistant

Logs and screenshots 📂

No response

[ldoench]

I figured out, that the Moon Illumination Fraction is only updated on every restart of ha, not continiously.

AI gave me two solutions, that I will try out later this week:

Method 1: Implementing SCAN_INTERVAL (sensor.py)
If the integration updates entities independently, define an update interval and an update method.

Add the import and interval definition at the top of the file:

from datetime import timedelta

SCAN_INTERVAL = timedelta(minutes=15)

Add the async_update method to the primary sensor class (e.g., LunarPhaseSensor):

    async def async_update(self):
        """Fetch new state data for the sensor."""
        # Replace 'self._calculate_data' with the integration's actual calculation method
        new_data = await self.hass.async_add_executor_job(self._calculate_data)
        
        # Update the property linked to the sensor state
        if self.entity_description.key == "illumination_fraction":
            self._attr_native_value = new_data.get("illumination_fraction")

Method 2: Implementing DataUpdateCoordinator (init.py and sensor.py)
If the integration fetches data centrally for all sensors, configure a DataUpdateCoordinator.

In init.py or the coordinator script, define the polling interval:

from datetime import timedelta
from homeassistant.helpers.update_coordinator import DataUpdateCoordinator, UpdateFailed
import async_timeout

async def async_setup_entry(hass, entry):
    # ... existing initialization code ...
    
    async def async_update_data():
        try:
            async with async_timeout.timeout(10):
                # Replace 'get_lunar_data()' with the actual backend call
                return await hass.async_add_executor_job(get_lunar_data)
        except Exception as err:
            raise UpdateFailed(f"Update failed: {err}")

    coordinator = DataUpdateCoordinator(
        hass,
        _LOGGER,
        name="lunar_phase",
        update_method=async_update_data,
        update_interval=timedelta(minutes=15), # Forces calculation every 15 minutes
    )
    
    await coordinator.async_config_entry_first_refresh()
    # ... continue setup ...

In sensor.py, wrap the sensor classes with CoordinatorEntity:

from homeassistant.helpers.update_coordinator import CoordinatorEntity
from homeassistant.components.sensor import SensorEntity

class LunarPhaseSensor(CoordinatorEntity, SensorEntity):
    def __init__(self, coordinator, description):
        super().__init__(coordinator)
        self.entity_description = description

    @property
    def native_value(self):
        """Return the state of the sensor from the coordinator."""
        return self.coordinator.data.get(self.entity_description.key)