# Mercury examples¶

Let’s define a small helper function:

```def print_me(msg, val):

print("{}: {}".format(msg, val))
```

We can compute the geometric heliocentric position for a given epoch:

```epoch = Epoch(2018, 10, 27.0)

lon, lat, r = Mercury.geometric_heliocentric_position(epoch)

print_me("Geometric Heliocentric Longitude", lon.to_positive())

# Geometric Heliocentric Longitude: 287.4887

print_me("Geometric Heliocentric Latitude", lat)

# Geometric Heliocentric Latitude: -6.0086

```

Compute the geocentric position for 1992/12/20:

```epoch = Epoch(1992, 12, 20.0)

ra, dec, elon = Mercury.geocentric_position(epoch)

print_me("Right ascension", ra.ra_str(n_dec=1))

# Right ascension: 16h 33' 59.3''

print_me("Declination", dec.dms_str(n_dec=1))

# Declination: -20d 53' 31.6''

print_me("Elongation", elon.dms_str(n_dec=1))

# Elongation: 18d 24' 29.8''
```

Print mean orbital elements for Mercury at 2065.6.24:

```epoch = Epoch(2065, 6, 24.0)

l, a, e, i, ome, arg = Mercury.orbital_elements_mean_equinox(epoch)

print_me("Mean longitude of the planet", round(l, 6))

# Mean longitude of the planet: 203.494701

print_me("Semimajor axis of the orbit (UA)", round(a, 8))

# Semimajor axis of the orbit (UA): 0.38709831

print_me("Eccentricity of the orbit", round(e, 7))

# Eccentricity of the orbit: 0.2056451

print_me("Inclination on plane of the ecliptic", round(i, 6))

# Inclination on plane of the ecliptic: 7.006171

print_me("Longitude of the ascending node", round(ome, 5))

# Longitude of the ascending node: 49.10765

print_me("Argument of the perihelion", round(arg, 6))

# Argument of the perihelion: 29.367732
```

Compute the time of the inferior conjunction close to 1993/10/1:

```epoch = Epoch(1993, 10, 1.0)

conjunction = Mercury.inferior_conjunction(epoch)

y, m, d = conjunction.get_date()

d = round(d, 4)

date = "{}/{}/{}".format(y, m, d)

print_me("Inferior conjunction date", date)

# Inferior conjunction date: 1993/11/6.1449
```

Compute the time of the superior conjunction close to 1993/10/1:

```epoch = Epoch(1993, 10, 1.0)

conjunction = Mercury.superior_conjunction(epoch)

y, m, d = conjunction.get_date()

d = round(d, 4)

date = "{}/{}/{}".format(y, m, d)

print_me("Superior conjunction date", date)

# Superior conjunction date: 1993/8/29.3301
```

Compute the time and angle of the western elongation close to 1993/11/1:

```epoch = Epoch(1993, 11, 1.0)

time, elongation = Mercury.western_elongation(epoch)

y, m, d = time.get_date()

d = round(d, 4)

date = "{}/{}/{}".format(y, m, d)

print_me("Western elongation date", date)

# Western elongation date: 1993/11/22.6386

elong = round(elongation, 4)

print_me("Maximum western elongation angle", elong)

# Maximum western elongation angle: 19.7506
```

Compute the time and angle of the eastern elongation close to 1990/8/1:

```epoch = Epoch(1990, 8, 1.0)

time, elongation = Mercury.eastern_elongation(epoch)

y, m, d = time.get_date()

d = round(d, 4)

date = "{}/{}/{}".format(y, m, d)

print_me("Eastern elongation date", date)

# Eastern elongation date: 1990/8/11.8514

elong = round(elongation, 4)

print_me("Maximum eastern elongation angle", elong)

# Maximum eastern elongation angle: 27.4201
```

Compute the time of the station in longitude #1 close to 1993/10/1:

```epoch = Epoch(1993, 10, 1.0)

sta1 = Mercury.station_longitude_1(epoch)

y, m, d = sta1.get_date()

d = round(d, 4)

date = "{}/{}/{}".format(y, m, d)

print_me("Date of station in longitude #1", date)

# Date of station in longitude #1: 1993/10/25.9358
```

Compute the time of the station in longitude #2 close to 1993/10/1:

```epoch = Epoch(1993, 10, 1.0)

sta2 = Mercury.station_longitude_2(epoch)

y, m, d = sta2.get_date()

d = round(d, 4)

date = "{}/{}/{}".format(y, m, d)

print_me("Date of station in longitude #2", date)

# Date of station in longitude #2: 1993/11/15.0724
```

Find the epoch of the Perihelion closer to 2000/01/01:

```epoch = Epoch(2000, 1, 1.0)

e = Mercury.perihelion_aphelion(epoch)

y, m, d, h, mi, s = e.get_full_date()

peri = str(y) + '/' + str(m) + '/' + str(d) + ' at ' + str(h) + ' hours'

print_me("The Perihelion closest to 2000/1/1 happened on", peri)

# The Perihelion closest to 2000/1/1 happened on: 2000/2/15 at 18 hours
```

Compute the time of passage through an ascending node:

```epoch = Epoch(2019, 1, 1)

time, r = Mercury.passage_nodes(epoch)

y, m, d = time.get_date()

d = round(d, 1)

print("Time of passage through ascending node: {}/{}/{}".format(y, m, d))

# Time of passage through ascending node: 2018/11/24.7

print("Radius vector at ascending node: {}".format(round(r, 4)))

# Radius vector at ascending node: 0.3143
```