October 2025 Observing Guide
- Andrew Wood
- 9 hours ago
- 5 min read
The following describes objects in our night sky for October and is especially written for beginning observers.
Moon Phases
The Deep Sky Objects described later should be visible with the Moon present, although they will be better seen at times when the Moon is not visible. Still, don’t be put off by the Moon if the sky is clear. See what you can and try again on a moonless night.
October starts with the Moon having just passed First Quarter, becoming more gibbous each day until…
Oct 7: Full Moon – rising around sunset. Afterwards, it wanes through gibbous phases toward…
Oct 14: Last Quarter – rising around midnight. Afterwards, it wanes through crescent phases toward…
Oct 21: New Moon – rising and setting with the Sun. No moon visible all night. Afterwards, it waxes through crescent phases toward…
Oct 30: First Quarter - the Moon rises about midday and sets about midnight.
Planets
Saturn is the only bright planet easily visible to observe this month. It has just passed Opposition and is already well up in the east as dark sets in. A small aperture telescope will show the planet’s rings, currently nearly edge-on from our perspective. Titan, the biggest of Saturn’s moons, will also be visible in a small telescope. Surface features will require a larger telescope, which may also show several fainter moons.
A twilight conjunction of Mercury and Mars will occur in the late afternoon twilight in the west. They will be close from 19th – 23rd, and on the 23rd the crescent Moon will also be in the picture. This is mainly a naked-eye event, although imaging will be worth a try. You will need a fairly clear western horizon.
To view Jupiter, which rises about 1am, you will need to be out a couple of hours before dawn.
Another reason to be out before dawn is the Orionid Meteor Shower, which peaks on the 21st at New Moon and may produce 20 or more meteors per hour.
Deep Sky Objects
[Refer to the article: DEEP SKY 101 | Shoalhaven Astronomers on an external website for information about the types of Deep Sky Objects.]
Compared with the September 2025 post, the picture below shows a wider area around Scorpius and Sagittarius at 10PM Eastern Daylight-Saving time during October. This area of sky abounds in deep sky objects, mainly clusters and nebulae. If you have access to a atlas, either a book or digital, and a telescope, you can spend many nights over many years exploring this region. Those objects described here are some more bright examples which can be located with binoculars and are good objects for a small telescope.
The following are descriptions of the numbered objects [see the end of this article for a primer on terms such as magnitude, M and NGC]
1. NGC 6231, also known as the False Comet Nebula and the Northern Jewel Box, is, at magnitude 2.6, a very bright and large Open Cluster adjacent to the star zeta-Scorpii, which is at the kink in the scorpion’s tail. In a good sky its nature can be seen with the naked-eye and easily in binoculars. A small telescope at low magnification gives a great view. The Cluster is 5,900 light years away.
2. M62, also called NGC 6266, is a Globular Cluster located at the tip of an equilateral triangle with the two stars in Scorpius’s tail directly above Antares. It has a magnitude of 6.6 and is 22,500 light years away.
3. M28, also called NGC 6626, is a Globular Cluster located close to lambda-Sagittarii. It has a magnitude of 6.9 and is 19,000 light years away. [On the other side of lambda-Sagittarii, and closer to the star than M28, is another Globular Cluster, NGC 6638. At mag 9.2 it is much fainter.]
4. M11, also o called NGC 6705, and the wonderful name of Wild Duck Cluster, is a bright Open Cluster rich in stars, located in Scutum, The Shield. The main stars in Scutum are only of magnitude 4, so it a faint constellation. M11 is located nearby to beta-Scuti, the second brightest stars of the group. The cluster is magnitude 5.8 and is 5,500 light years away.
5. Beta-Sagittarii. Above the main “Teapot” asterism of Sagittarius is a faint but distinct curved group of stars in the constellation Corona Australis, The Southern Crown. Above them, in the outskirts of Sagittarius, lies its second brightest star, beta-Sagittarii. It is actually a naked-eye double, β-1 and β-2. β-1 is itself double, with components of mag 4.0 and 7.2 separated by 29”. Even a small telescope will show the fainter companion.
6. NGC 6441. I have added this as it is fainter and smaller than the objects above, but so near to the star G-Scorpii – just off the tail-end of Scorpius – it is very easy to find. Aiming a telescope at the star will show a fuzzy spherical patch nearby, obviously a Globular Cluster. NGC 6441 is magnitude 7.4 and lies 34,000 light years away.
Some Useful Terms
Aperture is the diameter of the lens or mirror that the telescope uses to collect light.
Magnitude is how bright an object is. Smaller Numbers have Brighter Magnitudes – e.g. Magnitude 1 is brighter than magnitude 2. A very dark sky will allow stars as faint as magnitude 6 to be visible. Very bright objects – bright stars and planets, the Moon and Sun, have negative magnitudes.
Magnification, or Power, is calculated by dividing the focal length of a telescope by the focal length of the eyepiece being used. For example, if you are using a telescope with a focal length of 600mm and an eyepiece of focal length 20mm, the magnification will be 600/30 = 20. This is usually expressed as 20X.
M stands for objects in the Messier Catalogue of 110 objects. This was one of the earliest lists of deep sky objects compiled in the 1700s. Most of the objects in this catalogue will also have an NGC number.
NGC stands for New General Catalogue. All Deep Sky Objects will have a catalogue number, of which the NGC is the most well-known, with more than 7,000 objects. Many brighter, more well-known objects have names such as Jewel Box, Blue Planetary etc. All of these will also have a number in one of the many astronomical catalogues.
FOR THOSE NEW TO AMATEUR ASTRONOMY
I strongly advise that you purchase or borrow books, or read online sites, devoted to teaching basic Astronomy. Teach yourself about:
Different types of telescopes
Aperture and Focal Length
Magnification
Eyepieces, Barlow lenses and filters
Navigating the night sky
Planispheres
Star Atlases
Right Ascension and Declination
Deep Sky Objects – clusters, nebulae and galaxies
Andrew Wood