The Pleiades Star Cluster

Plot

Dwarf 3

Starplot

Winter in the Northern Hemisphere brings us some of the most beautiful open star clusters, including the well-known Pleiades (also known as the Seven Sisters or Messier 45). It's so popular that it even has its own subreddit - /ItsAlwaysPleiades 😆

I recently got a Dwarf 3 smart telescope to help with testing Starplot and improving its star-sizing algorithms, and decided to make the Pleiades my first target. Above you'll see the photo I took with the Dwarf 3 vs the optic plot I created with Starplot. I think Starplot did a pretty good job with the star sizes and colors here, but it is missing a lot of stars (mostly because Starplot is currently limited to the Tycho-2 star catalog). I'm looking forward to using much bigger star catalogs (like Gaia) in Starplot, which will be possible in the next version :)

How to See It

• 📅 When: Fall to winter every year
• 🌎 Where (on Earth): Visible from Northern Hemisphere
• 👀 Where (in the sky): Look east (it will move west across the sky as we get deeper into winter)
• 🔭 What you need: Just your eyes or binoculars to see individual stars. The red dashed circle in the image above shows the field of view when looking through 10x binoculars.

---

Source Code

Python 3.12 Starplot 0.17.1

from datetime import datetime
from zoneinfo import ZoneInfo

from starplot import (
    HorizonPlot,
    OpticPlot,
    PlotStyle,
    style_extensions,
    DSO,
    Observer,
    Camera,
    Binoculars,
    callables,
    _,
)

""" 
Observer Details 
--------------------------------
November 29, 2025 @ 7:11pm PT
Poway, CA (USA)
"""

tz = ZoneInfo("US/Pacific")
dt = datetime(2025, 11, 29, 19, 11, 0, 0, tzinfo=tz)
observer = Observer(
    dt=dt,
    lat=32.7678,
    lon=-117.023,
)

m45 = DSO.get(m="45")

"""
Horizon Plot
--------------------------------
"""

horizon = HorizonPlot(
    azimuth=(45, 125),
    altitude=(0, 45),
    observer=observer,
    resolution=2048,
    style=PlotStyle().extend(
        style_extensions.BLUE_NIGHT,
        style_extensions.MAP,
        style_extensions.GRADIENT_ASTRONOMICAL_TWILIGHT,
    ),
    scale=0.6,
)

horizon.stars(
    where=[_.magnitude < 2.4],
    where_labels=[_.magnitude < 2],
    style__marker__symbol="star_4",
    color_fn=callables.color_by_bv,
)

horizon.horizon(
    labels={
        90: "Looking East",
        135: None,
    }
)

horizon.optic_fov(
    ra=m45.ra,
    dec=m45.dec,
    optic=Binoculars(
        magnification=10,
        fov=65,
    ),
)

horizon.constellations(where=[_.iau_id == "ori"])

with horizon.style.dso_open_cluster as oc:
    oc.marker.color = "hsl(210, 29%, 8%)"
    oc.marker.edge_width = 4
    oc.marker.dash_capstyle = "butt"
    oc.label.font_size = 36
    oc.label.font_weight = "bold"
    oc.label.offset_x = 38
    oc.label.offset_y = 20
    horizon.dsos(where=[_.m == "45"], label_fn=lambda d: "The Pleiades (M45)")

horizon.export("horizon.svg", format="svg", padding=0.2)


"""
Optic Plot
--------------------------------
Using a Dwarf 3 smart telescope 
"""

dwarf3 = Camera(
    # the dwarf 3's sensor is really 7.7mm wide, 
    # but I cropped the image to a square so I made the sensor square
    sensor_width=4.3,  
    sensor_height=4.3,
    lens_focal_length=150,
)

p = OpticPlot(
    ra=3.7795 * 15,
    dec=24.071,
    optic=dwarf3,
    observer=observer,
    style=PlotStyle().extend(
        style_extensions.GRAYSCALE_DARK,
        style_extensions.OPTIC,
        {
            "figure_background_color": "#000",
            "border_bg_color": "#000",
        },
    ),
    resolution=2048,
    autoscale=True,
)

p.stars(
    where=[_.magnitude < 14],
    where_labels=[False],
    catalog="big-sky",
    color_fn=callables.color_by_bv,
)

p.export("plot.svg", format="svg", padding=None)