RASC Hamilton

The Summer Triangle (all night)
2025-07-12 20:00 - 2025-07-13 05:00 (America/Toronto)
After dusk in mid-July, the first stars to appear in the darkening eastern sky are Vega, Deneb, and Altair. Those three bright, white stars form the Summer Triangle asterism – an annual feature of the summer sky that remains visible until the end of December! The highest and most easterly of the trio is Vega, in Lyra. At magnitude 0.03, Vega is the brightest star in the summer sky, mainly due to its relative proximity. It’s only 25 light-years away from the sun. Magnitude 0.75 Altair, in Aquila, occupies the lower right (southern) corner of the triangle. Altair is 17 light-years from the sun. By contrast, Deneb, which shines somewhat less brightly at magnitude 1.25, is a staggering 2,600 light-years away from us; but it shines so brightly because of its greater intrinsic luminosity. Once the bright moon departs next week, watch for the Milky Way passing between Vega and Altair and through Deneb.

Saturn Stands Still (wee hours)
2025-07-14 00:00
On Monday morning, July 14, the regular eastward motion of Saturn through the background stars of western Pisces will slow to a stop as it prepares to execute a westerly retrograde loop (red curve) that will last until the end of November. The apparent reversal in Saturn’s motion is an effect of parallax produced when Earth, on a faster orbit closer to the sun, passes the Ringed Planet on the “inside track”. Saturn’s retrograde loop will altogether cover about a palm’s width (or 7 degrees) of the celestial sphere, though there aren’t any bright stars near Saturn to make that motion obvious.

Bright Moon Shines above Saturn and Neptune (overnight)
2025-07-15 20:00 - 2025-07-16 05:00
A short time after the bright, waning gibbous moon clears the treetops in the east around midnight on Tuesday evening, July 15, the prominent, yellowish dot of Saturn will climb to join it – close enough to the moon for them to share the view in binoculars (orange circle). The very faint blue planet Neptune will be positioned just a finger’s width above Saturn, but a telescope will be required to see it well. The trio will cross the sky together and shine about halfway up the southern sky as dawn breaks on Wednesday morning.

Third Quarter Moon (at 00:38 GMT on Friday)
2025-07-17 19:00 - 22:00
The moon will complete three quarters of its orbit around Earth, measured from the previous new moon, on Thursday, July 17 at 8:38 p.m. EDT or 5:38 p.m. PDT, which converts to Friday at 02:52 GMT. At the third (or last) quarter phase the moon appears half-illuminated on its western, sunward side. It will rise around midnight local time, and then remain visible until it sets in the western daytime sky in early afternoon. Third quarter moons are positioned ahead of the Earth in our trip around the Sun. About 3½ hours later, Earth will occupy that same location in space. The week of dark, moonless evening skies that follow this phase are the best ones for observing deep sky targets.

The Stinging Scorpion (evening)
2025-07-18 19:00 - 22:00
After dusk in mid-July, the distinctive constellation of Scorpius, the Scorpion reaches its peak elevation over the southern horizon. The constellation’s brightest star is orange-tinted Antares, the “Rival of Mars”. Several medium-bright, white stars arranged in a roughly vertical line to the west of Antares mark the creature’s claws on modern sky charts; however, the major stars of neighboring Libra used to perform that role. The rest of the scorpion extends to the south and curls to the left (celestial eastward) into the Milky Way, terminating with the bright double star Shaula, which marks its poisonous stinger. Observers at high mid-northern latitudes might not be able to see the southernmost stars of the constellation.

Crescent Moon Crosses the Pleiades (pre-dawn)
2025-07-20 00:00
In the eastern sky before dawn on Sunday morning, July 20, the pretty, waning crescent moon will shine very close to the bright little Pleiades Star Cluster (aka The Seven Sisters, Subaru, and Messier 45) in Taurus. The pairing will show nicely in binoculars (orange circle). For skywatchers in the Americas, the moon will pass directly through the cluster’s stars starting at about 4:25 a.m. EDT or 08:25 GMT. By the time that the moon completes its passage around two hours later, the sky will be brightening in the Eastern and Central time zones, but it will still be dark in the Pacific Time zone. Keep an eye out for the blue-green speck of Uranus to the lower right of the Pleiades all year.

Pretty Moon Poses with Venus and Jupiter (before sunrise)
2025-07-21 00:00
After 24 hours of additional eastward motion, the more slender crescent of the waning moon will make a lovely sight while it shines above the brilliant planet Venus in the east before sunrise on Monday, July 21. The pair can be enjoyed, and photographed, between the time that Venus rises at about 3 a.m. local time and sunrise. The very bright planet Jupiter will gleam to their lower left once it rises at around 4 a.m. local time. On Tuesday morning, the moon will shift to a position between Jupiter and Venus.

Sliver of Moon Meets Jupiter (before sunrise)
2025-07-23 00:00
The old crescent moon will complete its visit with the bright morning planets on Wednesday, July 22, when its slim, 2.5%-illuminated sliver will shine less than a palm’s width to the left (or 5 degrees to the celestial northeast) of brilliant Jupiter. Before the sun begins to rise, you can place Jupiter on the right edge of your binoculars’ field of view (orange circle) and find to the moon on the left.

New Moon (at 19:11 GMT)
2025-07-24 19:00 - 22:00
On Thursday, July 24 at 3:11 p.m. EDT or 12:11 p.m. PDT, or 19:11 GMT, the moon will officially reach its new moon phase. At that time our natural satellite will be located in Cancer, 3.4 degrees north of the sun. While new, the moon is travelling in space between Earth and the sun. Since sunlight can only illuminate the far side of the moon, and the moon is in the same region of the sky as the sun, it becomes completely hidden from view from anywhere on Earth for about a day (unless there’s a solar eclipse). After the new moon phase, Earth’s celestial night-light will return to shine as a crescent in the western evening sky.

Pluto at Opposition (all night)
2025-07-25 20:00 - 2025-07-26 05:00
On the nights surrounding Friday morning, July 25, the dim and distant dwarf planet designated (134340) Pluto will reach opposition for 2025. On that date, the Earth will be positioned between Pluto and the sun, minimizing our distance from that outer world and maximizing Pluto’s visibility. While at opposition, Pluto will be located 3.28 billion miles, 5.28 billion km, or 285 light-minutes from Earth. Unfortunately, it will shine with an extremely faint visual magnitude of +14.4 that is far too dim for visual observing through a small backyard telescope. Pluto will be located in southwestern Capricornus, about a palm’s width to the upper right (or 5.9 degrees to the celestial WNW) of the medium-bright star Psi Capricorni and to the lower left of the globular star cluster Messier 75. Even if you can’t see Pluto directly, you will know that it is there.

Slim Crescent Moon near Regulus (after sunset)
2025-07-26 17:30 - 19:30
For a short time after sunset on Saturday, July 26, the extremely slender crescent of the young moon will shine above the western horizon. As the sky darkens, Leo’s brightest star Regulus will appear just to the lower right (or celestial west) of the moon – close enough for them to share the view in binoculars (orange circle). Observers closer to the tropics, where the ecliptic will be more vertical, will see their conjunction more easily.

Crescent Moon Flees Mars (after sunset)
2025-07-28 17:30 - 19:30
As the sky begins to darken after dusk on Monday, July 28, look low in the western sky for reddish Mars shining several finger widths to the upper right (or 3 degrees to the celestial north) of the waxing moon’s slender crescent – close enough for them to share the view in binoculars (orange circle). Since the moon continuously slides east by its own diameter every hour, observers in Europe and Africa will see the moon close below Mars, while those in the western Americas and the Pacific Ocean region will see the moon farther to the left of Mars.

Southern Delta-Aquariids Meteors Peak (wee hours)
2025-07-29 19:00 - 22:00
The annual Southern Delta-Aquariids meteor shower lasts from July 18 to August 21. In 2025 it will peak during the wee hours of Tuesday morning, July 29 in the Americas, but it is quite active for a week surrounding the peak night. The best viewing time will run from late Monday evening until the sky starts to brighten on Tuesday morning. The waxing crescent moon will not affect the shower this year. The Southern Delta-Aquariids shower, produced by debris dropped from the periodic Comet 96P/Machholz, commonly generates 15-20 meteors per hour at the peak. It is best enjoyed from the southern tropics, where the shower’s radiant, in southern Aquarius, climbs higher in the sky. (Image – Jul29-2025 at 1 am – Southern Delta-Aquariids Meteor Shower Peaks.jpg)

Crescent Moon near Spica Again (evening)
2025-07-30 19:00 - 22:00
After a previous visit on July 3, the moon’s trip around Earth will bring it back to shine near Virgo’s brightest star Spica again on Wednesday evening, July 30. As darkness falls, look low in the western sky for bright, white Spica twinkling several finger widths to the upper left (or celestial east) of the pretty crescent moon. Skywatchers located in more westerly time zones will see the moon closer to the star – clear evidence of our natural satellite’s orbital motion. (Image – Jul30-2025 at 930 pm – Crescent Moon near Spica Again.jpg)Planets
Skywatching Terms
Gibbous: Used to describe a planet or moon that is more than 50% illuminated.
Asterism: A noteworthy or striking pattern of stars within a larger constellation.
Degrees (measuring the sky): The sky is 360 degrees all the way around, which means roughly 180 degrees from horizon to horizon. It’s easy to measure distances between objects: Your fist on an outstretched arm covers about 10 degrees of sky, while a finger covers about one degree.
Visual Magnitude: This is the astronomer’s scale for measuring the brightness of objects in the sky. The dimmest object visible in the night sky under perfectly dark conditions is about magnitude 6.5. Brighter stars are magnitude 2 or 1. The brightest objects get negative numbers. Venus can be as bright as magnitude minus 4.9. The full moon is minus 12.7 and the sun is minus 26.8.
Terminator: The boundary on the moon between sunlight and shadow.
Zenith: The point in the sky directly overhead.
Night Sky Observing Tips
Adjust to the dark: If you wish to observe fainter objects, such as meteors, dim stars, nebulas, and galaxies, give your eyes at least 15 minutes to adjust to the darkness. Avoid looking at your phone’s bright screen by keeping it tucked away. If you must use it, set the brightness to minimum – or cover it with clingy red film.
Light Pollution: Even from a big city, one can see the moon, a handful of bright stars, and the brightest planets – if they are above the horizon. But to fully enjoy the heavens — especially a meteor shower, the fainter constellations, or to see the amazing swath across the sky that is the disk of our home galaxy, the Milky Way — rural areas are best for night sky viewing. If you’re stuck in a city or suburban area, use a tree or dark building to block ambient light (or moonlight) and help reveal fainter sky objects. If you’re in the suburbs, simply turning off outdoor lights can help.
Prepare for skywatching: If you plan to be outside for more than a few minutes, and it’s not a warm summer evening, dress more warmly than you think is necessary. An hour of winter observing can chill you to the bone. For meteor showers, a blanket or lounge chair will prove to be much more comfortable than standing, or sitting in a chair and craning your neck to see overhead.
Daytime skywatching: On the days surrounding first quarter, the moon is visible in the afternoon daytime sky. At last quarter, the moon rises before sunrise and lingers into the morning daytime sky. When Venus is at a significant angle away from the sun it can often be spotted during the day as a brilliant point of light – but you’ll need to consult an astronomy app to know when and where to look for it. When large sunspots develop on the sun, they can be seen without a telescope – as long as you use proper solar filters, such as eclipse glasses. Permanent eye damage can occur if you look at the sun for any length of time without protective eyewear.
