...

cxx/mcc_mount_telemetry.h

@@ -138,8 +138,13 @@ public:
     typedef HARDWARE_T hardware_t;
     typedef DATA_T mount_telemetry_data_t;
 
+
     typedef std::error_code error_t;
 
+    struct coord_diff_t {
+        typename ASTROM_ENGINE_T::coord_t xdiff, ydiff, r2;
+    };
+
     MccMountTelemetry(astrom_engine_t& astrom_engine, pec_t& pec, hardware_t& hardware)
         : base_t(astrom_engine, pec), _hardware(hardware)
     {
@@ -162,7 +167,30 @@ public:
         return err;
     }
 
+    // target - mount coordinate difference
+    auto targetToMountDiff()
+    {
+        std::lock_guard lk(_updateMutex);
 
+        coord_diff_t result;
+
+        if constexpr (mccIsEquatorialMount(pec_t::mountType)) {
+            result.xdiff = _data.tagRA - _data.mntHA;
+            result.ydiff = _data.tagDEC - _data.mntDEC;
+        } else if constexpr (mccIsAltAzMount(pec_t::mountType)) {
+            result.xdiff = _data.tagAZ - _data.mntAZ;
+            result.ydiff = _data.tagALT - _data.mntALT;
+        } else {
+            static_assert(false, "UNSUPPORTED MOUNT TYPE!");
+        }
+
+        result.r2 = result.xdiff * result.xdiff + result.ydiff * result.ydiff;
+
+        return result;
+    }
+
+
+    // update telemetry right now
     error_t update()
     {
         mount_telemetry_data_t current_data;
@@ -278,7 +306,7 @@ public:
         return MccMountTelemetryErrorCode::ERROR_OK;
     }
 
-    // wait until data is updated or given timeout occurs
+    // wait (block current thread) until data is updated or given timeout occurs
     template <traits::mcc_time_duration_c DT>
     error_t waitForUpdatedData(mount_telemetry_data_t& data, const DT& timeout)
     {