? ? ? ? 在天文學上，地方恒星時就是觀測地的中天赤經坐標。在天文望遠鏡自動尋星系統中，地方恒星時是系統解算赤道儀姿態的重要依據，通過計算赤道儀的中天位置赤經坐標，自動尋星控制系統可以得知天文望遠鏡指向的方位角和高度角，從而得知赤道儀自動尋星路線和模式，還可以在導星時判斷赤道儀中天翻轉的時機，當觀測天體越過中天時即進行中天翻轉。以下代碼可以較為準確的計算觀測地的地方恒星時，利用Visual Studio 2019 C++編寫，讀者可下載天文通或者其他星圖軟件驗證程序計算當地恒星時的準確性。

頭文件：Time_Conversioner.h

#pragma once #include<iostream> #include<cmath> class Angle_To_Time { public:int Hour;int Min;int Sec;/*顯示時、分、秒單位制下的赤經坐標*/void Printf_(){std::cout << Hour << " h " << Min << " min " << Sec << " sec " << std::endl;} };class Time_Conversioner { public:/*得到地方恒星時，輸出的是角度坐標表示*/double Sidereal_time();/*得到地方恒星時，輸出的是赤徑的時、分、秒坐標表示*/Angle_To_Time RA_Zenith();/*得到緯度*/double Get_Altitude();/** @brief 將赤經坐標轉換為角度，1小時=15°，1分=0.25度，1秒=0.25/60度。@param Hour_ 赤經小時@param Min_ 赤經分鐘@param Sec_ 赤經秒*/double Time2Angle(double Hour_, double Min_, double Sec_);/** @brief 將不在0~360°區間內的角度通過加減360°讓其進入這個區間@param Input_angle 需要轉換的角度*/double Angle_in_0_360(double Input_angle);/** @brief 設置當前觀測地的經度、緯度@param latitude 經度@param altitude 緯度*/void set_observation_place(double latitude, double altitude); private:double latitude = 110;//經度double altitude = 30;//緯度double Date_Now;double Mouth_Now;double Year_Now;double Hour_Now;double Min_Now;double Second_Now;struct tm* ptminfo;time_t rawtime;Angle_To_Time Get_RA;double Get_Year();double Get_Mouth();double Get_Date();double Get_Hour();double Get_Min();double Get_Sec();void Time_Update();double JD_time();/*0h UT平恒星時*/double Sidereal_time_0_UT();Angle_To_Time Angle2Time(double Input_Angle); };

源文件：Time_Conversioner.cpp

#define _CRT_SECURE_NO_WARNINGS 1 #include"Time_Conversioner.h"Angle_To_Time Time_Conversioner::RA_Zenith() {Angle_To_Time OUTPUT;OUTPUT = Angle2Time(Sidereal_time());return OUTPUT; }double Time_Conversioner::Get_Altitude() {return this->altitude; }void Time_Conversioner::set_observation_place(double latitude, double altitude) {this->latitude = latitude;this->altitude = altitude; }double Time_Conversioner::JD_time(){Time_Update();double JD = 0;double Mouth_Now_ = Mouth_Now;double Year_Now_ = Year_Now;double Date_Now_ = Date_Now;if (Mouth_Now_ == 1 || Mouth_Now_ == 2){Mouth_Now_ += 12;Year_Now_ -= 1;}JD = floor(abs(365.25 * (Year_Now_ + 4716.0))) + floor(abs(30.6001 * (Mouth_Now_ + 1))) + \2 - floor(Year_Now_ / 100.0) + floor(floor(Year_Now_ / 100.0) * 0.25) + Date_Now_ - 1524.5;return JD; }double Time_Conversioner::Sidereal_time_0_UT(){//求得的是角度值double JD = 0;double T = 0;double ST = 0;JD = JD_time();T = (JD - 2451545.0) / 36525;ST = 100.46061837 + 36000.770053608 * T + 0.000387933 * T * T - T * T * T / 38710000;if (ST < 0 || ST>360){if (ST < 0){while (ST<0){ST += 360;}}else if(ST>360){while (ST>360){ST -= 360;}}}return ST; }double Time_Conversioner::Sidereal_time(){double ST_UT0 = Sidereal_time_0_UT();double m_ = Time2Angle(Hour_Now, Min_Now, Second_Now) + (latitude - 8.0 / 24.0 * 360);double M_ = m_ - latitude;double Mu = M_ / 365.2422;double OUTPUT;OUTPUT = m_ + ST_UT0 + Mu;if (OUTPUT > 360.0){while (OUTPUT>360.0){OUTPUT -= 360.0;}}if (OUTPUT < 0.0){while (OUTPUT<0.0){OUTPUT += 360.0;}}return OUTPUT; }double Time_Conversioner::Get_Mouth(){double MOUTH_ = 0;MOUTH_ = double(ptminfo->tm_mon + 1.0);return MOUTH_; }double Time_Conversioner::Get_Date(){double DATE_;DATE_ = double(ptminfo->tm_mday);return DATE_; }double Time_Conversioner::Get_Year(){double YEAR_;YEAR_ = double(ptminfo->tm_year + 1900.0);return YEAR_; }double Time_Conversioner::Get_Hour(){double HOUR_;HOUR_ = double(ptminfo->tm_hour);return HOUR_; }double Time_Conversioner::Get_Min(){double MIN_;MIN_ = double(ptminfo->tm_min);return MIN_; }double Time_Conversioner::Get_Sec(){double SEC_;SEC_ = double(ptminfo->tm_sec);return SEC_; }void Time_Conversioner::Time_Update(){time(&rawtime);ptminfo = localtime(&rawtime);Date_Now = Get_Date();Mouth_Now = Get_Mouth();Year_Now = Get_Year();Hour_Now = Get_Hour();Min_Now = Get_Min();Second_Now = Get_Sec();//std::cout << Year_Now << " " << Mouth_Now << " " << Date_Now << " " << Hour_Now << " " << Min_Now << " " << Second_Now << std::endl; }double Time_Conversioner::Time2Angle(double Hour_, double Min_, double Sec_){return Hour_ / 24.0 * 360.0 + Min_ / (24.0 * 60.0) * 360.0 + Sec_ / (24.0 * 60.0 * 60.0) * 360.0; }double Time_Conversioner::Angle_in_0_360(double Input_angle){double OUTPUT = Input_angle;if (OUTPUT > 360.0){while (OUTPUT > 360.0){OUTPUT -= 360.0;}}else if (OUTPUT < 0){while (OUTPUT<0){OUTPUT += 360.0;}}return OUTPUT; }Angle_To_Time Time_Conversioner::Angle2Time(double Input_Angle){Angle_To_Time OUTPUT;int Hour_;int Min_;int Sec_;double Angle = Input_Angle;Hour_ = floor(Angle / 15.0);Angle = Angle - Hour_ * 15.0;Min_ = floor(Angle / (0.25));Angle = Angle - Min_ * 0.25;Sec_ = floor(Angle / (0.25 / 60));OUTPUT.Hour = Hour_;OUTPUT.Min = Min_;OUTPUT.Sec = Sec_;Get_RA = OUTPUT;return OUTPUT; }

示例代碼：

void main() {Time_Conversioner Timer;Timer.set_observation_place(102, 26);//設置觀測地經度、緯度while (1){Timer.RA_Zenith().Printf_();//打印當前的當地恒星時，該值每秒更新一次Sleep(1000);} }

運行結果：?

總結

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