First and fourth contact times don't match with illustrations

[irfanimaduddin]

Mas, gambar ilustrasi dengan nilai separasi yang didapat tidak cocok (terutama kontak 1 dan 4). Begitu pula dengan waktu kontaknya.

Kontak 1 (Gambar) Kontak 1 (Asli)

Kontak 4 (Gambar) Kontak 4 (Asli)

[ubutnux]

It's impossible to debug without the exact code. Please provide the code with some explanation what are you trying to do.

[irfanimaduddin]

Sorry, lupa. Saya berusaha untuk memvisualisasikan kontak 1 dan 4 dari referensi yang sudah ada. Tetapi ternyata ilustrasi dan waktu tidak sesuai. Berikut kodenya.

siak = EarthLocation(lat=0.9277778*u.deg, lon=104.4175*u.deg, height=1*u.m) #Pulau Penyengat
tz = pytz.timezone('Asia/Jakarta')
waktu_tebakan = Time(tz.localize(datetime.datetime(2019,12, 26, 13, 53, 0)))

altAzframe = AltAz(obstime=waktu_tebakan, location=siak)

matahariAltAz = get_sun(waktu_tebakan).transform_to(altAzframe)
bulanAltAz = get_moon(waktu_tebakan).transform_to(altAzframe)

separasi = matahariAltAz.separation(bulanAltAz).to(u.arcmin)
separasi

from astropy import constants

R_matahari = constants.R_sun
R_bulan = 1737.1 * u.km

def ukuran_tampak(R, jarak):
    return (R/jarak).to(u.arcmin, u.dimensionless_angles())

ukuranMatahari = ukuran_tampak(R_matahari, matahariAltAz.distance)
ukuranMatahari

ukuranBulan = ukuran_tampak(R_bulan, bulanAltAz.distance)
ukuranBulan

lingkaranMatahari = plt.Circle((matahariAltAz.az.deg, matahariAltAz.alt.deg), 
                        ukuranMatahari.to(u.deg).value,
                        fc='yellow')
lingkaranBulan = plt.Circle((bulanAltAz.az.deg, bulanAltAz.alt.deg), 
                         ukuranBulan.to(u.deg).value,
                         fc='black', alpha=.5)

ax = plt.subplot(aspect=1)
ax.add_patch(lingkaranMatahari)
ax.add_patch(lingkaranBulan)
jarakTerbesar = max(separasi.deg, ukuranMatahari.to(u.deg).value, ukuranBulan.to(u.deg).value)
plt.xlim(matahariAltAz.az.deg-.9, matahariAltAz.az.deg+.5)
plt.ylim(matahariAltAz.alt.deg-.65, matahariAltAz.alt.deg+.625)
plt.text(matahariAltAz.az.deg-.75, matahariAltAz.alt.deg-.35, 'r_matahari = %s arcmin' %(ukuranMatahari.value),
         color='black', verticalalignment='center', horizontalalignment='left')
plt.text(matahariAltAz.az.deg-.75, matahariAltAz.alt.deg-.425, 'r_bulan = %s arcmin' %(ukuranBulan.value),
         color='black', verticalalignment='center', horizontalalignment='left')
plt.text(matahariAltAz.az.deg-.75, matahariAltAz.alt.deg-.5, 'separasi = %s arcmin' %(separasi.value),
         color='black', verticalalignment='center', horizontalalignment='left')
plt.text(matahariAltAz.az.deg-.75, matahariAltAz.alt.deg-.575, 'waktu = '+waktu_tebakan.value.strftime('%H:%M:%S UTC'),
         color='black', verticalalignment='center', horizontalalignment='left')

#plt.title('D_matahari = %s; D_bulan = %s; sep = %s' %(ukuranMatahari.value, ukuranBulan.value, separasi.value))
plt.xlabel('Azimut (derajat)')
plt.ylabel('Altitud (derajat)')

plt.savefig('Pulau Penyengat (kontak_4 gambar).png')

[ubutnux]

if you just want to calculate the first and the fourth contact, please see the updated notebook https://github.com/ubutnux/gmc2019/commit/a004fce56cbe85436a46dc846175983775a7af28.

You have to be very careful with that big plot. When you are dealing with a big field of view you have to project 3 dimensional spaces into 2 dimensional spaces. I just don't have time right now to deal with the coordinate transformation. You can read the detail information on astropy WCS module.

[irfanimaduddin]

I see. Thanks a lot!

Irfan Imaduddin Bosscha Observatory Institut Teknologi Bandung Lembang, Indonesia 40391

Pada tanggal Rab, 28 Agu 2019 pukul 00.34 ubutnux notifications@github.com menulis:

if you just want to calculate the first and the fourth contact, please see the updated notebook a004fce https://github.com/ubutnux/gmc2019/commit/a004fce56cbe85436a46dc846175983775a7af28 .

You have to be very careful with that big plot. When you are dealing with a big field of view you have to project 3 dimensional spaces into 2 dimensional spaces. I just don't have time right now to deal with the coordinate transformation. You can read the detail information on astropy WCS module.

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