Skywatcher's Guide: August and September 2020


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 (during observatory hours)

Name / Designation Apparent Magnitude
(lower = brighter)
Arcturus -0.05 36.7  
Vega 0.03 25  
Capella 0.08 42  
Altair 0.76 17  
Spica 0.98 262  
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

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Solar System

Mercury will be passing behind the Sun in mid-August, but will become visible again in the evening sky in the second half of September.

Venus is now visible in the morning sky before sunrise, reaching its highest point in mid-August..

Mars comes up earlier each night, passing through the constellation of Pisces.

Jupiter now rises before sunset just to the left of the Sagittarius Teapot.

Saturn sits right next to Jupiter, in between Sagittarius and Capricornus.

Jupiter Great Red Spot Transits during August and September (when the Flandrau dome is open)

Note: The GRS is visible on the disk of Jupiter for 50 minutes before and after meridian transit time.

Date Meridian Transit Time
08/07/20 08:12 PM
08/14/20 08:57 PM
08/21/20 09:44 PM
09/05/20 07:08 PM
09/12/20 07:55 PM
09/17/20 07:04 PM
09/19/20 08:43 PM
09/24/20 07:52 PM
09/26/20 09:30 PM

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Calendar of Night Sky Events

Date Event


Full Moon.


Last Quarter Moon.


Peak of Perseids meteor shower.


Venus at greatest western elongation. — Visible before sunrise.


Mercury at superior conjunction. — Passing behind the Sun.


New Moon.


First Quarter Moon.


Full Moon.


Last Quarter Moon.


Neptune at opposition. — Best time to see our farthest planet.


New Moon.


Earth at Southward Equinox. Beginning of our Fall.


First Quarter Moon.


Appulse of Saturn and Pluto — Separated by 2.9°.

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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 (during observatory hours)

Designation Name Apparent Magnitude Apparent Size Distance

Messier 45





open cluster

Messier 31

Andromeda Galaxy


3° x 1°


spiral galaxy

Messier 33

Triangulum Galaxy


67' x 42'


spiral galaxy

Messier 3

(in Canes Venatici)




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




planetary nebula

Messier 81

Bode's Galaxy




spiral galaxy

Messier 57 Ring Nebula 8.8 1' 2,300 planetary nebula

Messier 82

Cigar Galaxy





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Frequently Asked Questions

What is a nebula?


Simply put, a nebula is a cloud in space.  Similar to clouds we see here on Earth, they are loosely bound accumulations of particles, usually gas but sometimes dust or ice particles as well.  You have almost certainly seen images of nebulae from the Hubble Space Telescope or other large telescopes.  These images are often very colorful and have inspired a lot of artwork featuring outer space.

There are two main categories of nebulae: either they have not yet been part of a star, or they come from a dying star.  The first kind are known as diffuse nebulae because they usually have no particular shape to them.  Sometimes they glow, and sometimes they do not, depending on whether or not there are stars nearby or within the nebula.  Usually these nebulae appear red or pink in natural-color photos due to the high abundance of hydrogen.  Hydrogen is the most abundant element in the universe, and often times it clumps up due to gravity, making these nebulae.  If there is enough, it can start creating new stars.  Some examples of these are the Swan Nebula, the Eagle Nebula, the Lagoon Nebula, and the Orion Nebula.

Dark nebulae are a little more of a challenge to find and photograph, for obvious reasons.  Usually we notice them by the light that they block.  For example, the arm of the MIlky Way is very thick with stars, but there are some dark patches scattered across it.  These dark patches are not empty space, but rather dark nebulae blocking the starlight from behind them.  Some examples of these are the Coalsack Nebula, the Horsehead Nebula, and the Cone Nebula.

When stars die, they release the material from within them out into space.  These nebulae typically are much more colorful due to the range of different materials that they are made of, such as oxygen, carbon, nitrogen, etc.  These nebulae are created either very slow or very fast.  The slower version is known as a planetary nebula.  It doesn't really have anything to do with planets, but were named as such because they sometimes resemble perfect spheres through a telescope.  They sometimes also have a bilobed shape similar to an hourglass or butterfly.  This happens when the dying star has something nearby like a debris disk or another stellar companion.  Some examples of planetary nebulae are the Ring Nebula, the Helix Nebula, the Dumbbell Nebula, and the Eskimo Nebula.

Finally, when a star dies in a supernova, it spews its material out much more quickly and over a wider area.  These remnants can contain traces of gold, platinum, titanium, and other heavy elements.  They often have roughly circular or oval shapes, but at high detail, you can see much more chaotic patterns within them.  Some examples of supernova remnants are the Veil Nebula, the Crab Nebula, and Cassiopeia A.

Nebulae are some of my favorite objects to look at through a telescope.  They all have slightly different appearances and are strikingly different from the simple pinpoints of stars.  When the Milky Way is out (as it is this time of year) there are many nebulae that can be found within and nearby its arms.  So if you get the chance, I highly recommend taking a look!


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!

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  • Cornelius, Geoffrey. The Starlore Handbook: an Essential Guide to the Night Sky. San Francisco, CA: Chronicle, 1997. Print.
  • Ottewell, Guy. Astronomical Calendar 2012. Raynham, Mass: Universal Workshop, 2011. Print.
  • Ottewell, Guy. Astronomical Calendar 2013. Raynham, Mass: Universal Workshop, 2012. Print.
  • Ottewell, Guy. The Astronomical Companion. 2nd ed. Raynham, Mass: Universal Workshop, 2010. Print.
  • Astronomy Magazine. February 2013. Volume 41, No 2.
  • Astronomy Magazine. February 2013. Volume 41, No 3.
  • Sky & Telescope. February 2013. Volume 125, No 2.
  • Sky & Telescope. March 2013. Volume 125, No 3.

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