Time-of-Day Observing Guide: Day, Dusk, Night and Dawn

Time-of-Day Observing Guide: Day, Dusk, Night and Dawn

What to observe at each time of day from Guyana, from the daytime Sun to the pre-dawn Milky Way, with Georgetown times.

All times are Guyana time (America/Guyana, UTC-4, no daylight saving) and are for Georgetown unless stated.

The day at a glance

Near 7° N the clock times barely change through the year, so this table works in every month.

| Window | Georgetown clock | What to do | |---|---|---| | Daytime | Sunrise to late afternoon | Filtered Sun, sunspots, shadows | | Late afternoon | 1 to 2 hours before sunset | Check the weather, plan the night | | Twilight | Sunset (about 17:31 to 18:12) to full dark | Young Moon, Venus, green flash, ISS | | Early night | Full dark (about 18:45 to 19:30) to midnight | Main session, sky test, southern sky | | Late night and pre-dawn | Midnight to sunrise (about 05:35 to 06:11) | Milky Way core, zodiacal light, morning planets |

Daytime: the Sun and its shadows

Sun safety comes first

Never look at the Sun without proper protection. Unfiltered sunlight can cause permanent eye damage, and through binoculars, a telescope or a camera viewfinder the harm is almost instant.

Aim a filtered telescope by its shadow: the tube's shadow shrinks to a small circle when it points at the Sun.

What to see on the Sun

Try this: a one-week sunspot count

For one week, at the same time each day (say 10:00), count and sketch the sunspot groups through a front filter or on a projected image. Did the count rise, fall or stay the same? You will also see the spots drift as the Sun rotates: a spot takes about 13 days to cross the disc. Observatories make this count daily for the international sunspot number.

Shadows and the overhead Sun

In Guyana the Sun passes straight overhead at noon twice a year: about 6 April and 4 September at Georgetown, and about 28 March and 13 September at Lethem. These dates fall two to three weeks from the equinoxes. On those days an upright pole casts almost no shadow at local noon, a good day for a shadow photo or a sundial experiment.

The Sun Path Today, Hour by Hour lists the Sun's height and direction for each hour of today at your location; check it on a zero-shadow day and again a month later to see the arc shift. To record that arc on paper over months, follow the solargraphy lesson. Before a solar eclipse, check local times in Solar Eclipse Times & Local View, and follow the same filter rules.

Late afternoon: plan the night

Use the hour or two before sunset to plan:

  1. Open Stargazing Weather for cloud, humidity, dew risk and transparency, hour by hour.
  2. Check Tonight Observing Score for a quick Go, Maybe or Skip.
  3. Get twilight times from Sun/Moon Times & Dark Window, and see how much a bright Moon will cost you in the Moonlight Impact Calculator.
  4. Pick 3 to 5 targets from Tonight's Top 3 Highlights, Planets Visible Tonight and Sky Events.
  5. Charge batteries, clean eyepieces, and pack a red light.

Seeing and transparency

| Tonight's air | Best targets | |---|---| | Steady and clear | Anything: planets, double stars, faint galaxies | | Unsteady but clear | Wide-field views, star clusters, the Milky Way | | Steady but hazy | Bright planets, the Moon, double stars | | Unsteady and hazy | The Moon at low power, or a processing night |

Sunset and twilight

At Georgetown the Sun sets between about 17:31 (early November) and 18:12 (July). Near the equator the Sun drops almost straight down, so twilight is short.

| Stage | Starts after sunset (Georgetown) | What changes | |---|---|---| | Civil dusk | 21 to 23 minutes | Bright planets and stars appear | | Nautical dusk | 45 to 50 minutes | The horizon fades, most bright stars show | | Astronomical dusk | 69 to 77 minutes | Full dark, faint objects come through |

Full darkness starts between about 18:45 in early November and 19:30 in early July. The Golden & Blue Hour Timeline gives exact times for your date and place.

Sunset to full dark and back to sunrise, for any month at Georgetown or Lethem.

One evening over Georgetown, 15 October 2026, from sunset to full dark: where each twilight ends, and why near the equator full dark comes about 70 minutes after sunset in every month.

The young Moon and earthshine

One to four days after New Moon, a thin crescent appears low in the west just after sunset. Near the equator the Moon's path stands steeply above the horizon at dusk, so thin crescents are easier to catch than at higher latitudes. Its dark part glows faintly grey with earthshine, sunlight reflected off Earth onto the Moon ("the old Moon in the new Moon's arms"). You can see it with your eyes, and binoculars show it well.

To photograph it, use a tripod: a few seconds records the earthshine but burns out the crescent, so add a much shorter frame and blend the two. The Moon and Lunar Phenomena lesson explains when each phase is up.

Planets at dusk

Venus and Mercury appear only near dusk or dawn, never at midnight. Venus sets at most about 3 hours after the Sun, so dusk is your only window for an evening Venus. Low planets look redder because you look through much more air near the horizon, and that thicker air dims and reddens light. Jupiter's cream and Saturn's pale gold are their own colours at any height. Planets Visible Tonight shows rise, peak and set times, and the Solar System Overview lesson explains why the inner planets stay near the Sun.

The green flash

Over a flat, clear horizon, the last sliver of the setting Sun sometimes flashes green for a second or two. Refraction splits sunlight into colours, and mirages near the horizon help make the flash visible.

Guyana has no sea horizon to the west: the coast faces northeast, and at Georgetown the Sun always sets over land (between about 246° and 294° azimuth). For a sunset attempt, find a flat western horizon such as the Rupununi savannahs. On the coast, try at sunrise over the Atlantic instead. Never aim binoculars or a camera viewfinder at the Sun, even a low one. Watch with your eyes alone, and stop looking once the full disc clears the horizon.

The ISS and satellites

Satellites are easiest to see after sunset or before sunrise, when you are in darkness but the satellite is still in sunlight. Use the ISS Pass Predictor for times and directions, and Is the ISS Visible Tonight? to read the pass labels.

Early night: full dark to midnight

A simple session plan

  1. First 20 to 30 minutes: set up, review your list, and use only a dim red light while your eyes adapt to the dark.
  2. Next hour: start with bright targets (the Moon, a planet, a bright cluster) to check focus, seeing and transparency.
  3. After that: try your hardest targets, such as faint galaxies, close doubles and planetary detail.

Test your sky with the Pleiades

A star count tells you which faint objects are worth trying tonight. Many guides use the Little Dipper (Ursa Minor), but from 6.8° N it stays low in the north (Polaris about 7° up, Kochab about 23°) and sits in haze. Use the Pleiades instead, an evening target from about October to March. Count the stars you see without optics, as a rough guide:

A limit of about 5.1 to 5.5 matches Bortle class 6, a bright suburban sky. What Is the Bortle Scale? explains each class and how to find darker sites.

The Pleiades drawn to a limiting magnitude: slide until the count matches what you see.

The southern sky from Guyana

The Local Sky Sphere shows where these sit at the moment you open it. The Milky Way core is an evening sight from about July to October, and the Milky Way Season Planner gives the best hours for each month.

Late night and pre-dawn

Between New Moon and First Quarter the Moon sets by about midnight, so the late night stays dark.

The Milky Way core before dawn

From about February to May the Milky Way core is a pre-dawn target. In mid-April its centre crosses the south at about 04:00, high in a dark sky. Astronomical dawn begins between about 04:20 (early June) and 05:00 (early February), 69 to 77 minutes before sunrise. Milky Way Season Near the Equator covers the season month by month, including the rainy months.

Zodiacal light

Zodiacal light is a faint cone of light rising along the zodiac, sunlight scattered by dust between the planets. Look in the east before dawn or in the west after dusk. From mid-northern latitudes it is best on spring evenings and autumn mornings. From Guyana the zodiac stands steeply in twilight all year, so you can look for it in any month from a dark site with no Moon. The numbers show why: at the end of evening twilight (Sun 18° down) the ecliptic stands at least 60° to Georgetown's western horizon in every month of 2027, and at least 59.8° (in April) to the eastern horizon before dawn. From New York it falls to 26° on late-summer evenings. That is geometry only: a city sky like Georgetown's still hides the light, so go to a dark site. The helper below works out the angle and the Moon for any town and night.

The ecliptic's angle to the horizon at the end of twilight, and the Moon, for Georgetown, Lethem or New York on any of the next 60 nights.

Morning planets and sunrise

When Venus is a morning star, it rises before the Sun and climbs in the eastern pre-dawn sky. Mercury sometimes appears low in the east near dawn. At Georgetown the Sun rises between about 05:35 (May) and 06:11 (late January). Cap all optics before sunrise.

When clouds roll in

Use a cloudy night to stack last session's frames in Siril, or practise a stretch, a colour calibration or a noise reduction pass. Then check Stargazing Weather for the next clear window.

The 30-day sky journal

Each night, note the date, time, place, conditions and what you saw.

| Days | Focus | |---|---| | 1-7 | Naked eye only. Identify 5 constellations visible from Guyana | | 8-14 | Track one planet against the background stars every other day | | 15-21 | Sketch the Moon daily and record each phase | | 22-28 | Deep sky, or solar observing with a front filter, each clear day | | 29-30 | Review. What changed? What surprised you? What next? |

Activity: find your best window tonight

  1. Note the time now and match it to a section of this guide.
  2. Name one thing you could observe now or in the next two hours.
  3. Write it down, then check the weather for that hour.

Test yourself

The night is clear, but distant lights on the horizon look wavy and blurred. Is it a good night for detail on Saturn?

Poor seeing (unsteady air) spoils high-magnification planetary views. Choose wide-field targets tonight, or wait for a steadier night.

At 19:00 Venus is bright in the west. You plan to watch it all night. What is wrong with this plan?

Venus never strays more than about 47° from the Sun and sets at most about 3 hours after it, so it is below the horizon by midnight. Observe it at dusk.

What does a limiting magnitude of 5.5 tell you about your site?

It points to a bright suburban sky (Bortle class 6). Clusters and bright nebulae are fine in binoculars or a telescope, but the Milky Way shows only faintly, near the zenith.

What's next

Take this plan outside with a telescope in First Telescope Night, which covers setup, first targets and an observing log.

Tools · Learn