diff --git a/sternwarte-homeassistant-card/README.md b/sternwarte-homeassistant-card/README.md
index 3a04bc4..5da2e3e 100644
--- a/sternwarte-homeassistant-card/README.md
+++ b/sternwarte-homeassistant-card/README.md
@@ -6,9 +6,12 @@ Lovelace-Card für die Sternwarte.
 
 ```text
 dist/
+  astronomy.browser.min.js
   sternwarte-card.js
 ```
 
+`sternwarte-card.js` lädt `astronomy.browser.min.js` automatisch nach, um Dämmerungszeiten und Mondposition präziser zu berechnen.
+
 ## Für HACS
 
 Dieser Ordner ist als Root eines späteren HACS-Dashboard-Repositorys vorbereitet.
diff --git a/sternwarte-homeassistant-card/dist/sternwarte-card.js b/sternwarte-homeassistant-card/dist/sternwarte-card.js
index e4bf57d..9d32ea4 100644
--- a/sternwarte-homeassistant-card/dist/sternwarte-card.js
+++ b/sternwarte-homeassistant-card/dist/sternwarte-card.js
@@ -14,6 +14,14 @@ const DEFAULT_ENTITIES = {
   astroLon: 11.0481766,
 };
 
+const ASTRONOMY_LIB_URL = (() => {
+  try {
+    return new URL("./astronomy.browser.min.js", import.meta.url).toString();
+  } catch (error) {
+    return null;
+  }
+})();
+
 class SternwarteCard extends HTMLElement {
   constructor() {
     super();
@@ -22,9 +30,11 @@ class SternwarteCard extends HTMLElement {
       close: { draft: "", editing: false, pending: false },
     };
     this._pendingRender = false;
+    this._astronomyLoadPromise = null;
   }
 
   connectedCallback() {
+    this._ensureAstronomy();
     this._ensureClockTimer();
   }
 
@@ -71,6 +81,46 @@ class SternwarteCard extends HTMLElement {
     }, 30000);
   }
 
+  _astronomy() {
+    return window.Astronomy || null;
+  }
+
+  _ensureAstronomy() {
+    const astronomy = this._astronomy();
+    if (astronomy) return Promise.resolve(astronomy);
+    if (this._astronomyLoadPromise) return this._astronomyLoadPromise;
+    if (!ASTRONOMY_LIB_URL) return Promise.resolve(null);
+
+    this._astronomyLoadPromise = new Promise((resolve) => {
+      const finish = () => {
+        const loaded = this._astronomy();
+        if (loaded && this._hass) {
+          this._requestRender();
+        }
+        this._astronomyLoadPromise = null;
+        resolve(loaded || null);
+      };
+
+      const existing = Array.from(document.querySelectorAll("script"))
+        .find((script) => script.src === ASTRONOMY_LIB_URL);
+
+      if (existing) {
+        existing.addEventListener("load", finish, { once: true });
+        existing.addEventListener("error", finish, { once: true });
+        return;
+      }
+
+      const script = document.createElement("script");
+      script.src = ASTRONOMY_LIB_URL;
+      script.async = true;
+      script.addEventListener("load", finish, { once: true });
+      script.addEventListener("error", finish, { once: true });
+      document.head.appendChild(script);
+    });
+
+    return this._astronomyLoadPromise;
+  }
+
   _requestRender() {
     if (this._isScheduleEditing()) {
       this._pendingRender = true;
@@ -389,107 +439,83 @@ class SternwarteCard extends HTMLElement {
     return date >= lastSunday(2, 1) && date < lastSunday(9, 1);
   }
 
-  _calcTwilight(date) {
+  _astroObserver() {
+    const astronomy = this._astronomy();
+    if (!astronomy) return null;
     const lat = Number(this.config.astroLat);
     const lon = Number(this.config.astroLon);
-    const jd = date.getTime() / 86400000 + 2440587.5;
-    const n = jd - 2451545.0;
-    const L = ((280.460 + 0.9856474 * n) % 360 + 360) % 360;
-    const g = ((357.528 + 0.9856003 * n) % 360 + 360) % 360;
-    const gR = g * Math.PI / 180;
-    const lam = L + 1.915 * Math.sin(gR) + 0.020 * Math.sin(2 * gR);
-    const lamR = lam * Math.PI / 180;
-    const eps = 23.439 - 0.0000004 * n;
-    const epsR = eps * Math.PI / 180;
-    const dec = Math.asin(Math.sin(epsR) * Math.sin(lamR));
-    const RA = Math.atan2(Math.cos(epsR) * Math.sin(lamR), Math.cos(lamR)) * 180 / Math.PI / 15;
-    const GMST0h = ((L + 180) % 360 + 360) % 360 / 15;
-    const solarNoon = (12 - lon / 15 - (RA - GMST0h + 12 + 720) % 24 + 24) % 24;
-    const latR = lat * Math.PI / 180;
-
-    const eventUTC = (depDeg) => {
-      const cosH = (Math.sin(-depDeg * Math.PI / 180) - Math.sin(latR) * Math.sin(dec))
-        / (Math.cos(latR) * Math.cos(dec));
-      if (cosH < -1 || cosH > 1) return null;
-      const H = Math.acos(cosH) * 180 / Math.PI / 15;
-      return { dawn: (solarNoon - H + 24) % 24, dusk: (solarNoon + H) % 24 };
-    };
-
-    return {
-      sun: eventUTC(0.833),
-      civil: eventUTC(6),
-      naut: eventUTC(12),
-      astro: eventUTC(18),
-    };
+    if (!Number.isFinite(lat) || !Number.isFinite(lon)) return null;
+    return new astronomy.Observer(lat, lon, 0);
   }
 
-  _julianDate(date) {
-    return date.getTime() / 86400000 + 2440587.5;
+  _astroTimeToUtcHour(eventTime) {
+    if (!eventTime) return null;
+    const date = eventTime.date instanceof Date ? eventTime.date : null;
+    if (!date || Number.isNaN(date.getTime())) return null;
+    return date.getUTCHours() + date.getUTCMinutes() / 60 + date.getUTCSeconds() / 3600;
   }
 
-  _gmstHours(jd) {
-    const T = (jd - 2451545) / 36525;
-    const gmst = 280.46061837 + 360.98564736629 * (jd - 2451545) + 0.000387933 * T * T
-      - (T * T * T) / 38710000;
-    return (((gmst % 360) + 360) % 360) / 15;
+  _calcTwilight(date) {
+    const astronomy = this._astronomy();
+    const observer = this._astroObserver();
+    if (!astronomy || !observer) {
+      return {
+        sun: { dawn: null, dusk: null },
+        civil: { dawn: null, dusk: null },
+        naut: { dawn: null, dusk: null },
+        astro: { dawn: null, dusk: null },
+      };
+    }
+
+    try {
+      const bodySun = astronomy.Body?.Sun ?? "Sun";
+      const start = new Date(date);
+      start.setHours(0, 0, 0, 0);
+      const limitDays = 2;
+      const altitudeEvent = (altitude) => ({
+        dawn: this._astroTimeToUtcHour(astronomy.SearchAltitude(bodySun, observer, +1, start, limitDays, altitude)),
+        dusk: this._astroTimeToUtcHour(astronomy.SearchAltitude(bodySun, observer, -1, start, limitDays, altitude)),
+      });
+
+      return {
+        sun: {
+          dawn: this._astroTimeToUtcHour(astronomy.SearchRiseSet(bodySun, observer, +1, start, limitDays, 0)),
+          dusk: this._astroTimeToUtcHour(astronomy.SearchRiseSet(bodySun, observer, -1, start, limitDays, 0)),
+        },
+        civil: altitudeEvent(-6),
+        naut: altitudeEvent(-12),
+        astro: altitudeEvent(-18),
+      };
+    } catch (error) {
+      return {
+        sun: { dawn: null, dusk: null },
+        civil: { dawn: null, dusk: null },
+        naut: { dawn: null, dusk: null },
+        astro: { dawn: null, dusk: null },
+      };
+    }
   }
 
   _moonStateAt(date) {
-    const jd = this._julianDate(date);
-    const d = jd - 2451543.5;
-    const lat = Number(this.config.astroLat) * Math.PI / 180;
-    const lonHours = Number(this.config.astroLon) / 15;
-    const toRad = (deg) => deg * Math.PI / 180;
-    const normalizeDeg = (deg) => ((deg % 360) + 360) % 360;
+    const astronomy = this._astronomy();
+    const observer = this._astroObserver();
+    if (!astronomy || !observer) {
+      return { altitude: Number.NEGATIVE_INFINITY, illumination: 0 };
+    }
 
-    const sunMeanLongitude = normalizeDeg(280.460 + 0.9856474 * (jd - 2451545.0));
-    const sunMeanAnomaly = normalizeDeg(357.528 + 0.9856003 * (jd - 2451545.0));
-    const sunLongitude = normalizeDeg(
-      sunMeanLongitude + 1.915 * Math.sin(toRad(sunMeanAnomaly)) + 0.020 * Math.sin(2 * toRad(sunMeanAnomaly)),
-    );
+    try {
+      const bodyMoon = astronomy.Body?.Moon ?? "Moon";
+      const equator = astronomy.Equator(bodyMoon, date, observer, true, true);
+      const horizon = astronomy.Horizon(date, observer, equator.ra, equator.dec, "normal");
+      const illumination = astronomy.Illumination(bodyMoon, date);
 
-    const N = normalizeDeg(125.1228 - 0.0529538083 * d);
-    const i = toRad(5.1454);
-    const w = normalizeDeg(318.0634 + 0.1643573223 * d);
-    const a = 60.2666;
-    const e = 0.0549;
-    const M = normalizeDeg(115.3654 + 13.0649929509 * d);
-    const E = M + (180 / Math.PI) * e * Math.sin(toRad(M)) * (1 + e * Math.cos(toRad(M)));
-    const xv = a * (Math.cos(toRad(E)) - e);
-    const yv = a * (Math.sqrt(1 - e * e) * Math.sin(toRad(E)));
-    const v = Math.atan2(yv, xv);
-    const r = Math.sqrt(xv * xv + yv * yv);
-
-    const xh = r * (Math.cos(toRad(N)) * Math.cos(v + toRad(w)) - Math.sin(toRad(N)) * Math.sin(v + toRad(w)) * Math.cos(i));
-    const yh = r * (Math.sin(toRad(N)) * Math.cos(v + toRad(w)) + Math.cos(toRad(N)) * Math.sin(v + toRad(w)) * Math.cos(i));
-    const zh = r * Math.sin(v + toRad(w)) * Math.sin(i);
-
-    const moonLon = Math.atan2(yh, xh);
-    const moonLat = Math.atan2(zh, Math.sqrt(xh * xh + yh * yh));
-    const obliquity = toRad(23.4393 - 0.0000004 * d);
-
-    const xe = r * Math.cos(moonLon) * Math.cos(moonLat);
-    const ye = r * Math.sin(moonLon) * Math.cos(moonLat);
-    const ze = r * Math.sin(moonLat);
-
-    const xeq = xe;
-    const yeq = ye * Math.cos(obliquity) - ze * Math.sin(obliquity);
-    const zeq = ye * Math.sin(obliquity) + ze * Math.cos(obliquity);
-
-    const raHours = (((Math.atan2(yeq, xeq) * 180 / Math.PI) / 15) + 24) % 24;
-    const dec = Math.atan2(zeq, Math.sqrt(xeq * xeq + yeq * yeq));
-    const lstHours = (this._gmstHours(jd) + lonHours + 24) % 24;
-    const hourAngle = toRad((lstHours - raHours) * 15);
-    const altitude = Math.asin(
-      Math.sin(dec) * Math.sin(lat) + Math.cos(dec) * Math.cos(lat) * Math.cos(hourAngle),
-    );
-
-    const elongation = Math.acos(
-      Math.cos(moonLat) * Math.cos(moonLon - toRad(sunLongitude)),
-    );
-    const illumination = Math.max(0, Math.min(1, (1 - Math.cos(elongation)) / 2));
-
-    return { altitude, illumination };
+      return {
+        altitude: (Number(horizon?.altitude) || 0) * Math.PI / 180,
+        illumination: Math.max(0, Math.min(1, Number(illumination?.phase_fraction) || 0)),
+      };
+    } catch (error) {
+      return { altitude: Number.NEGATIVE_INFINITY, illumination: 0 };
+    }
   }
 
   _moonTrackState() {