Skywatcher's Guide written by: Lucas Snyder (Flandrau Planetarium Specialist)
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Stars and Constellations
In August we can still see part of the spring sky at the beginning of the night after sunset. The bright star Spica in the constellation Virgo is low in the west-southwest. A little higher in the west is even brighter Arcturus in the constellation Boötes. The easily recognizable Big Dipper (Ursa Major) is also visible in the northwest. You can use two stars in the end of the bowl to find Polaris, the north star, which is the end of the handle of the Little Dipper (Ursa Minor). Next, high in the middle of the sky we see the summer constellations, with the three bright stars of the Summer Triangle being the most prominent. Vega is the highest and brightest of the three, with Deneb below towards the east and Altair to the southeast. Then Scorpius with the bright star Antares is visible to the south-southwest, and the "teapot" of Sagittarius is nearby towards the south. The summer Milky Way is prominent this time of year stretching all the way across the sky from south-southwest to north-northeast. Next, the fall sky is beginning to rise in the east at the beginning of the night. The "great square" of Pegasus is low towards the east and Andromeda is adjacent to the northeast. Cassiopeia is a little higher in the northeast, and appears as a "W" this time of year.
In September, Boötes is now low in the sky towards the west-northwest. The Big Dipper is also very low in the northwest. Polaris and the Little Dipper are of course still in the North. Now Scorpius is low in the southwest, and we can see the Sagittarius "teapot" in the south-southwest. The Summer Triangle is still up in the middle of the sky, and the summer Milky Way is still a prominent streak across the sky. Next, Pegasus and Andromeda are higher in the east, and you might be able to find the Andromeda Galaxy. Cassiopeia is higher in the northeast and is starting to rotate to a "3" orientation. Finally, below that you may see Perseus along the horizon at the beginning of the night.
Interesting Stars Visible in August and September (from 7 to 10 pm)
| Name / Designation | Apparent Magnitude (lower = brighter) | Distance (light-years) | Notes |
|---|---|---|---|
| Arcturus | -0.05 | 36.7 | |
| Vega | 0.03 | 25 | |
| Altair | 0.76 | 17 | |
| Spica | 0.98 | 262 | |
| Fomalhaut | 1.16 | 25 | |
| Markab | 1.25 | 140 | |
| Deneb | 1.25 | 3230 | |
| Polaris | 1.97 | 431 | |
| Alpheratz or Sirrah | 2.07 | 97 | |
| Mirach | 2.07 | 199 | |
| Algol | 2.09 | 93 | variable star |
| Denebola | 2.14 | 36.2 | |
| Enif | 2.38 | 670 | |
| Almak | 2.1 / 5.0 & 6.3 | 355 | triple star system w/ 64 yr orbit |
| Albireo | 3.2 / 5.8 & 5.1 | 390 / 380 | possibly a triple star system |
| Eta Cassiopeiae | 3.5 / 7.4 | 19 | 480 yr orbit |
Solar System
Mercury is visible in the morning sky for the second half of August, but then passes behind the Sun in mid-September.
Venus is visible in the morning sky for all of August and September, low in the east.
Mars is getting lower in the west after sunset, moving through Leo and Virgo.
Jupiter is visible in the morning sky, getting a little higher each day. It is in the constellation Gemini.
Saturn rises a little earlier each evening, eventually coming up at sunset by the end of September. It is in the constellation Pisces.
Calendar of Night Sky Events
| Date | Event |
|---|---|
08/01/25 | First Quarter Moon. |
08/09/25 | Full Moon. |
08/11/25 | Appulse of Venus and Jupiter — Separated by 0.9°. |
08/12/25 | Peak of Perseids meteor shower. |
08/15/25 | Last Quarter Moon. |
08/19/25 | Mercury at greatest western elongation. — Visible before sunrise. |
08/22/25 | New Moon. |
08/30/25 | First Quarter Moon. |
09/07/25 | Full Moon and Total Lunar Eclipse. — Not visible from Tucson. |
09/13/25 | Mercury at superior conjunction. — Passing behind the Sun. |
09/14/25 | Last Quarter Moon. |
09/20/25 | Saturn at opposition. — Best time to see this ringed planet. |
09/21/25 | New Moon and Partial Solar Eclipse. — Not visible from Tucson. |
09/22/25 | Earth at Southward Equinox. — Beginning of our Fall. |
09/23/25 | Neptune at opposition. — Best time to see our farthest planet. |
09/29/25 | First Quarter Moon. |
Deep Sky
There are many deep sky objects we can see since the summer Milky Way is high in the sky. There are many open star clusters that can be seen with only binoculars scanning this part of the sky. For example we have the Butterfly Cluster (M6) and Ptolemy's Cluster (M7) near the tail of Scorpius. Further north there is the Wild Duck Cluster (M11) in the faint constellation of Scutum between Sagittarius and Aquila. There is also the asterism of the Coathanger between Aquila and Cygnus in the fainter constellation of Vulpecula. Next, heading towards the west we can see the Coma Star Cluster in the constellation of Coma Berenices, which is even visible naked-eye. The Pleiades (M45) will be visible later in the night, after midnight.
There are a several globular clusters we can see as well, as the center of our galaxy is the highest it gets for the year. Near the bright star Antares in Scorpius lies the globular cluster M4. In Sagittarius we also have the Teapot Cluster (M22). Of course we have the famous Hercules globular (M13) high in the east. Also, M15 is visible in the east near the head of Pegasus.
For nebulae, we have several in the plane of the galaxy, one of which is the Swan Nebula (M17) in Sagittarius, also known as the Omega Nebula. There is also the Lagoon Nebula (M8) nearby and the North America Nebula (C20) further north in Cygnus. For planetary nebulae we have the Ring Nebula (M57) in Lyra, the Dumbell Nebula (M27) in Vulpecula, and the Blue Snowball (C22) in Andromeda.
And now the galaxies: Although the Big Dipper is getting lower in the sky, you may still be able to find some of the galaxies in this part of the sky. We have the Whirlpool Galaxy (M51) and the Pinwheel Galaxy (M101) near the handle, and the Cigar Galaxy (M82) and Bode's Galaxy (M81) near the bowl. The spectacular Andromeda Galaxy (M31) is now coming up in the northeast, along with the nearby Triangulum Galaxy (M33).
Interesting Deep Sky Objects to Observe during August and September (from 7 to 10 pm)
| Designation | Name | Apparent Magnitude | Apparent Size | Distance (light-years) | Type |
|---|---|---|---|---|---|
| Messier 31 | Andromeda Galaxy | 3.4 | 3° x 1° | 2,900,000 | spiral galaxy |
| Messier 33 | Triangulum Galaxy | 5.7 | 67' x 42' | 3,000,000 | spiral galaxy |
| Messier 3 | (in Canes Venatici) | 6.2 | 18' | 34,000 | globular cluster |
| NGC 7293 | Helix Nebula | 7.3 | 16' | 450 | planetary nebula |
| Messier 27 | Dumbbell Nebula | 7.4 | 8' × 6' | 1,250 | planetary nebula |
| NGC 7009 | Saturn Nebula | 8 | 36" | 2,400 | planetary nebula |
| Messier 81 | Bode's Galaxy | 8.5 | 21' | 1,200,000 | spiral galaxy |
| Messier 57 | Ring Nebula | 8.8 | 1' | 2,300 | planetary nebula |
| Messier 82 | Cigar Galaxy | 9.5 | 14' | 1,200,000 | galaxy |
Frequently Asked Questions
What is special about the Vera Rubin Telescope?
You may have seen in the news recently that the Vera Rubin Telescope in Chile released its first images in June. The images were amazing, of course, but how does it compare to other telescopes we already have?
It’s actually not the largest telescope in the world, but it ties the Large Binocular Telescope (here in Arizona!) for having the largest diameter of a single mirror (8.4 meters). All three of these huge mirrors were made here at the University of Arizona. Rubin’s mirror is unique, however, because it is actually two mirrors combined in a single piece of glass. The primary mirror occupies the outer 1.7-m ring, while the tertiary mirror fills in the inner 5 meters with a different focal length. Combining the two mirrors this way helps reduce the overall size of the telescope and ensures that their two focal axes are always aligned.
Next is its field of view. Each image it takes is about 3.5 degrees across, or about 7 times the diameter of the full Moon. And yet the resolution is still very high, at only 0.2 arcseconds per pixel. If we equate that to Earth coordinates, that would be like taking a photo the size of Ohio and still being able to see details as small as a large van. Plus, each pixel records one of 65,536 shades of grey, making the total image size 6.4 gigabytes. For comparison, the images JWST takes are roughly 2 arcminutes across, with a resolution of 0.1 arcseconds.
During its primary mission, Rubin will take thousands of images every night for 10 years, creating a huge time-lapse of the universe. It is expected to record 20 billion galaxies, 17 billion stars in our Milky Way, and 6 million objects in our solar system. We will be able to see how things change in brightness, position, and even color over time, leading to many discoveries we can only imagine.
If you have any questions you'd like me to answer in the next issue of SWG, please let me know. I'm also happy to take suggestions or comments, and also pictures if you'd like to send them. Happy viewing!
Date of publication: 2025