def jd_sun_alt(alt, jdin, lat, longit):
delta = 0.002
alterr = 0.001
maxstep = 10000
i = 0
jdguess = jdin
#[raval, decval] = SunCoords(jdguess)
[raval, decval] = solar_equ_coords(jdguess)
lstval = LST(jdguess, longit)
alt2 = getalt(raval, decval, lstval, lat)
if abs(alt2 - alt) < alterr:
return jdin
jdguess = jdguess + delta
#[raval, decval] = SunCoords(jdguess)
[raval, decval] = solar_equ_coords(jdguess)
lstval = LST(jdguess, longit)
alt3 = getalt(raval, decval, lstval, lat)
err = alt3 - alt
if abs(err) < alterr:
return jdguess
deriv = (alt3 - alt2) / delta
while (abs(err) > alterr and i < maxstep):
jdguess = jdguess - err / deriv
#[raval, decval] = SunCoords(jdguess)
[raval, decval] = solar_equ_coords(jdguess)
lstval = LST(jdguess, longit)
alt3 = getalt(raval, decval, lstval, lat)
err = alt3 - alt
i = i + 1
if i == maxstep - 1:
sys.stderr.write(
"Error determining the time at which the sun is at a given altitude.\n"
)
#exit(2)
if (i >= maxstep - 1):
jdguess = -1000.
return jdguess
def gettwilightJD(alt, nightyr, nightmo, nightday, lat, longit):
# First determine jd at approximate true midnight (not corrected
# for equation of time) for this location.
jdut = julian_day(nightyr, nightmo, nightday, 24, 0, 0)
jdmidapprox = jdut - longit/15./24.
# Check if the sun is always above or below the altitude threshold on
# a given night.
#[raval, decval] = SunCoords(jdmidapprox)
[raval, decval] = solar_equ_coords(jdmidapprox)
if lat >= 0.0:
if 90.0 - lat + decval < alt:
# The sun is never up, set the start and stop times to be
# midnight +- 0.5
return [jdmidapprox -0.5, jdmidapprox + 0.5]
elif lat - (90.0 - decval) > alt:
# The sun is always up, set the start and stop times to be
# midnight
return [jdmidapprox, jdmidapprox]
else:
if 90.0 + lat - decval < alt:
return [jdmidapprox -0.5, jdmidapprox + 0.5]
elif -lat - (90.0 + decval) > alt:
# The sun is always up, set the start and stop times to be
# midnight
return [jdmidapprox, jdmidapprox]
# Select trial evening and morning JD values
ha = alt_to_HA(alt, decval, lat)
jdeveapprox = jdmidapprox - ha/360.0
jdeve = jd_sun_alt(alt, jdeveapprox, lat, longit)
jdmornapprox = jdmidapprox + ha/360.0
jdmorn = jd_sun_alt(alt, jdmornapprox, lat, longit)
return [jdeve, jdmorn]
def FindVisibleTransits(yearstart, monthstart, daystart, yearstop, monthstop, daystop, RA, Dec, Period, Epoch, HalfDuration, obslat, obslongit, obstz, twialt, objalt, objname, objprio, objfutype, magv, starobj):
# First generate a list of all transit start, stop, and midpoint times
# Within the given date range.
[jd1, jd2] = gettwilightJD(twialt, yearstart, monthstart, daystart, obslat, obslongit)
if yearstart != yearstop or monthstart != monthstop or daystart != daystop:
[jdtmp, jd2] = gettwilightJD(twialt, yearstop, monthstop, daystop, obslat, obslongit)
nstart1 = math.floor((jd1 - Epoch + HalfDuration)/Period)
nstop1 = math.floor((jd1 - Epoch - HalfDuration)/Period)
if nstart1 > nstop1:
# The object is in transit at evening twilight on the first night
nstart = nstart1
else:
nstart = math.floor((jd1 - Epoch)/Period) + 1
nstart2 = math.floor((jd2 - Epoch + HalfDuration)/Period)
nstop2 = math.floor((jd2 - Epoch - HalfDuration)/Period)
if nstart2 > nstop1:
# The object is in transit at morning twilight on the last night
nstop = nstart2
else:
nstop = math.floor((jd1 - Epoch)/Period)
jdcent = Epoch + Period*numpy.array(range(int(nstart),int(nstop+1)))
if len(jdcent) == 0:
# No transits are in this range
return []
# Covert the series of transit center BJDs from the ephemeris into JDs
command="vartools -i - -converttime input bjd output jd radec fix "+str(RA)+" "+str(Dec)+" -o - -quiet"
process = subprocess.Popen(command, stdout=subprocess.PIPE, stdin=subprocess.PIPE, shell=True)
s=""
for jd in jdcent:
s=s+"%.17g 0 0.1\n" % jd
(output, dum) = process.communicate(s)
jdcent_corr=[]
for f in output.split("\n"):
if len(f.split()) > 0:
jdcent_corr.append(float(f.split()[0]))
jdcent = numpy.array(jdcent_corr)
transits = []
# Now for each JD check if the object is above the horizon
# and the sun is below the threshold for either the ingress,
# midpoint, or egress
for jd in jdcent:
jdOOTstart = jd - HalfDuration - 0.0208333
jdstart = jd - HalfDuration
jdstop = jd + HalfDuration
jdOOTstop = jd + HalfDuration + 0.0208333
[rasun, decsun] = solar_equ_coords(jdstart)
lststart = LST(jdstart,obslongit)
altsunstart = getalt(rasun, decsun, lststart, obslat)
altstart = getalt(RA, Dec, lststart, obslat)
[rasun, decsun] = solar_equ_coords(jd)
lstcent = LST(jd,obslongit)
altsuncent = getalt(rasun, decsun, lstcent, obslat)
altcent = getalt(RA, Dec, lstcent, obslat)
[rasun, decsun] = solar_equ_coords(jdstart)
lststop = LST(jdstop,obslongit)
altsunstop = getalt(rasun, decsun, lststop, obslat)
altstop = getalt(RA, Dec, lststop, obslat)
if altsunstart < twialt and altstart > objalt:
flag = "I"
else:
flag = "-"
if altsuncent < twialt and altcent > objalt:
flag = flag+"B"
else:
flag = flag+"-"
if altsunstop < twialt and altstop > objalt:
flag = flag+"E"
else:
flag = flag+"-"
if flag != "---":
[rasun, decsun] = solar_equ_coords(jdOOTstart)
lstOOTstart = LST(jdOOTstart,obslongit)
altsunOOTstart = getalt(rasun, decsun, lstOOTstart, obslat)
altOOTstart = getalt(RA, Dec, lstOOTstart, obslat)
[rasun, decsun] = solar_equ_coords(jdOOTstop)
lstOOTstop = LST(jdOOTstop,obslongit)
altsunOOTstop = getalt(rasun, decsun, lstOOTstop, obslat)
altOOTstop = getalt(RA, Dec, lstOOTstop, obslat)
if altsunOOTstart < twialt and altOOTstart > objalt:
flag = "O"+flag
else:
flag = "-"+flag
if altsunOOTstop < twialt and altOOTstop > objalt:
flag = flag+"O"
else:
flag = flag+"-"
[yr, mo, da, hr, mi, se] = jd2cal(jd, obstz)
if hr >= 12:
yr1 = yr
mo1 = mo
da1 = da
hr1 = hr
mi1 = mi
se1 = se
[yr2, mo2, da2, hr2, mi2, se2] = jd2cal(jd+1.0, obstz)
else:
yr2 = yr
mo2 = mo
da2 = da
hr2 = hr
mi2 = mi
se2 = se
[yr1, mo1, da1, hr1, mi1, se1] = jd2cal(jd-1.0, obstz)
night = "%04d.%02d.%02d/%02d" % (yr1, mo1, da1, da2)
[yrsta, mosta, dasta, hrsta, mista, sesta] = jd2cal(jdstart, obstz)
[yrsto, mosto, dasto, hrsto, misto, sesto] = jd2cal(jdstop, obstz)
[ramoon, decmoon] = lunar_equ_coords(jd)
moonsep = angular_separation(RA, Dec, ramoon, decmoon)
ltstart = "%02d:%02d" % (hrsta, mista)
ltcent = "%02d:%02d" % (hr, mi)
ltstop = "%02d:%02d" % (hrsto, misto)
if objfutype == "pri" or objfutype == "sec":
transits.append(TransitEvent(objname, objprio, math.floor((jd - Epoch + HalfDuration)/Period), night, flag, jdstart, ltstart, altstart, jd, ltcent, altcent, jdstop, ltstop, altstop, moonsep, objfutype, magv, starobj))
elif objfutype == "odd" or objfutype == "even":
objNtran = int(round((jd - Epoch)/Period)) % 2
if objNtran == 0 and objfutype == "even":
priotoshow = objprio
elif objNtran == 1 and objfutype == "odd":
priotoshow = objprio
else:
priotoshow = "..."
transits.append(TransitEvent(objname, priotoshow, math.floor((jd - Epoch + HalfDuration)/Period), night, flag, jdstart, ltstart, altstart, jd, ltcent, altcent, jdstop, ltstop, altstop, moonsep, objfutype, magv, starobj))
for obj in transits:
obj.priority()
return transits