Aynamsa about flatlib

[joaoventura]

Hi there, unfortunately ayanamsas are not implemented in this library (yet)..

[aum7]

nor is ayanamsa topic understand clearly, in indian astrology. swisseph 'offers' 42 of them, nobody knows for sure which one is 'neo - the one'.
the one popularly used in ind.astro is lahiri, and if one checks the details, it is arbitrary (not based on any real observations), and it was changed after it became 'a standard one'.
in short, ind.astro is a mess.
ie, using ayanamsa, for signs calculation, moves entry of sun into aries for cca. 23 days (23 being average ayanamsa, out of 42, approx.) later -> indians celebrate spring 23 days too late. except if this fact is incorporated in their celebration dates.
mixed zodiac is gaining popularity - western signs and jyotisa naksatras (moon mansions) calculations.

s love nia

[sunambiar]

Can you include following code for calculating Ayanamsa:
(and include a constant for 'Chandra-Hari Ayanamsa'

#/*---------------------------------------------------------------*/
def JD(y, m, d, h, mn, s:float):
    # Provide y = negative y if Era is Before Common Era (BCE)
    era = "CE"
    if y == 0:
        print("There is no year 0 in the Julian system!")
        return -1
    elif y < 0:
        era = 'BCE'
        y = -y
    if (y == 1582 and m == 10 and d > 4 and d < 15):
        print("The dates 5 through 14 October, 1582, do not exist in the Gregorian system!")
        return -2
    # if y < 0: y = y + 1
    if era == 'BCE': y = -y + 1
    if m > 2:
        jy = y
        jm = m + 1
    else:
        jy = y - 1
        jm = m + 13
    
    intgr = int(math.floor(math.floor(365.25*jy) + math.floor(30.6001*jm) + d + 1720995))
    #print(intgr)
    #check for switch to Gregorian calendar
    gregcal = 15 + 31*(10 + 12*1582)
    if (d + 31*(m + 12*y) >= gregcal):
      ja = int(math.floor(0.01*jy))
      intgr += 2 - ja + int(math.floor(0.25*ja))
        
    #correct for half-day offset
    dayfrac = float(h)/24.0 - 0.5;
    if ( dayfrac < 0.0 ):
       dayfrac += 1.0
       intgr -= 1
	
    #ow set the fraction of a day
    frac = dayfrac + (float(mn) + s/60.0)/60.0/24.0
    #print(frac)

    #round to nearest second
    jd0 = (intgr + frac)*100000
    #print(jd0)
    jd  = int(math.floor(jd0))
    #print(jd)
    if (jd0 - jd > 0.5): 
        jd += 1
    return float(int(jd/100000))
 
#/*---------------------------------------------------------------*/ 
def jd (d, m, y):
    #long a, j, l;
    #float b;
    if (m < 3):
      m += 12
      y -= 1

    a = y/100
    b = float(30.6) * float(m+1)
    l = int(b)
    j = 365 * y + y/4 + l + 2 - a + a/4 + d
    return j
#/*---------------------------------------------------------------*/ 
def jd2000 (y, m, d, h, mt, s:float):
    return JD(y,m,d,h,mt,s)
    #//return (snDate.day2000(y,m,d,0,0,0.0,0));
#/*---------------------------------------------------------------*/ 
def precessionArc (jd1:float, jd2:float):
        pArc = 0.0
        t_period = 0.0
        Tperiod = 0.0
        jd2000 = 2451545.0
        t_period = (float(jd2 - jd1)) / 36525.0
        Tperiod = (float(jd1 - jd2000)) / 36525.0;
        #print(" JD2000 = " + jd2000 + " Calc=" + jd2000(2000,1,1,12,0,0))
        pArc = (5029.0966 + 2.22226*Tperiod - 0.000042*Tperiod*Tperiod) 
        pArc = pArc * t_period
        pArc = pArc + (1.11161 - 0.000127 * Tperiod)* t_period * t_period
        pArc = pArc - 0.000113 * t_period * t_period * t_period
        return (pArc/60.0/60.0)
#/*---------------------------------------------------------------*/ 
def chandraHari_Ayana (y, m, d, h, mt, s:float):
        jd1 = jd2000(231,3,21,15,30,0.0) # //Spring Equinox of 231 A.D. = 0 Ayanamsa
        jd2 = jd2000(y,m,d,h,mt,s)
        #//System.out.println("JD231 = " + jd1 + " Required for "+jd2);
        return (precessionArc(jd1, jd2))
#/*---------------------------------------------------------------*/ 
#/*---------------------------------------------------------------*/                
def hms2float(h, m, s):
    #tm = date.utcoffset.time()
    #tm = tzUTCoffset.time()
    #tmVal = (((tm[2] / 60) + tm[1]) / 60) + tm[0]
    tmVal = (((float(s) / 60.0) + float(m)) / 60.0) + float(h)
    return tmVal

#/*---------------------------------------------------------------*/

def ayan(ayan_opt:int, y, m, d, h, mt, sec, tz, aya_val:float):
    ret = 0.0
    chandraHariAyana = False
    j = jd(d, m, y)
    #h6 = float(h) + (float(mt) + float(sec)/60.0) / 60.0; 
    h6 = hms2float(h, mt, sec)
    timeZone = tz
    h6 = (h6 - timeZone - 12.0) / 24.0
    b6 = (float(j) - 694025.0 + h6) / 36525.0
    if ayan_opt == 1:
         ret = 21.013972 + 1.398191*b6;  # BVRaman 
    elif ayan_opt == 2:
        ret = chandraHari_Ayana(y, m, d, h, mt, s)
        #print("ChandraHari Ayana using Precsn Arc="+DMS.dms(ret))
        chandraHariAyana = True
    elif ayan_opt == 3:
        ret = aya_val;   # User specified 
    else:
        ret = 22.460148 + 1.396042*b6 + 3.08e-4*b6*b6 # NCLahiri - Default
    
    return ret

#/*---------------------------------------------------------------*/

[astrorigin]

My 2 cents:

You should try to translate that with appropriate SwissEph functions directly.

See https://www.astro.com/swisseph/swephprg.htm#_Toc78973611 (C API)
Or equivalent Python functions in Pyswisseph https://github.com/astrorigin/pyswisseph

And follow instructions for user-defined ayanamsa.

If that is not giving you satisfaction, you can discuss the problem here: https://groups.io/g/swisseph