With 2.793 billion km distance from the sun, Neptune is the eight and farthest planet in the Solar System. It is the fourth-largest planet by diameter and is the densest giant planet.
Appearing darker with a blueish color (caused by the presence of methane in its atmosphere) you are probably wondering with all these factors considered if you are able to observe it?
This was one of my first questions when getting into Astronomy; can I See Neptune With A Telescope? It is possible to observe Neptune with a telescope. Whilst it is definitely possible, consider that it will appear relatively small, and the power of your telescope will dictate whether you can observe the finer details like the blueish disks/ its moon Triton. Being the only planet found by mathematical prediction rather than by empirical observation; if you want to observe Neptune with ease then the best option is to use a high-spec computerized telescope. The Celestron NexStar 8 SE Telescope (available on Amazon), is perhaps the best telescope in this category.
Why Observe Neptune?
Neptune has been identified as the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet in our Solar System. It is 17 times the mass of our Earth.
Its atmosphere is made up of primarily Hydrogen, Helium, Hydrocarbons, Nitrogen and “Ices” (composed of Water, Ammonia, and Methane). Its landmass is composed entirely of ices and rock due to the temperature being around -218 degrees Celcius which is the reason in why it is often referred to as an Ice Giant. It is the Methane that accounts for the blueish color and nature of Neptune.
Neptune has a very active climate, with winds at a speed of 2,100km/s driving large storms that whirl through its upper atmosphere. The high speed winds track around the planet at speeds up to 600 meters per second – more than what occurs on any other planets in the Solar System.
With a magnitude of +8, Neptune is not visible with the Naked Eye. So if you’re looking to observe it then you’re going to need to consider your equipment and apparatus.
Can I See Neptune With A Telescope?
If you plan to observe Neptune with a Telescope, you are going to need a scope with enough power (both Magnification and Aperture) to unveil its disk-like nature in the night sky.
Keep in mind, that this is the furthest planet from the Earth, and is only roughly 2.3 arc seconds across in diameter. As an arc second is 1/60th of an Arc Minute, which in turn is 1/60th of a Degree! Even with a high-spec telescope, its important to set expectations in that Neptune will appear quite small.
So if you rely on a smaller and weaker telescope, the optics will not be able to provide you with enough light to be able to capture it, and sharpen the image enough for any real detail. If your magnification is limited, Neptune will only appear like a star.
Taking all this into account, the best telescope to observe Neptune is one that you can easily align, enables you to use higher magnification and has long focal-length and large Aperture. These factors will also enable you to closer observe Neptune’s brightest moon, Triton.
In my experience, and through my countless hours of research, an 8″ Aperture Telescope is ideal. This will provide you with much greater detail and clarity of Neptune and you will be able to see the small blue disk.
Now in terms of the Telescope itself you have a couple of options:
The first is a Dobsonian (Newtonian) Reflector:
Due to its design, a Dobsonion is optimized for observing distant or faint objects. So it would be ideal for observing Neptune. As its the furthest planet away, you will also be able to use an 8″ Dobsonion to observe all the other planets as well as deep sky objects (nebulae and galaxies) in great detail. The SkyWatcher Traditional is a great entry level choice, but the Orion SkyQuest XT8 Plus is the more premium option.
Secondly, and perhaps the more optimal choice, would be to get a Computerized Scope:
By having a GoTo mount and database (the better models having 40,000+ celestial objects +) you can automatically locate and track planets and other celestial objects for you and instantly. This is therefore ideal if you are a beginner. As Neptune is one of the most difficult planets to isolate, this is a great option. The Celestron NexStar 8 SE Telescope is one of the most well-respected scopes in this category.
Where To Find Neptune
If you are not using a Computerized Telescope (advised), then you are going to need to manually find Neptune before you can observe it.
It is much more difficult to find than the five brighter planets in the sky, all of which can actually be seen with the naked eye. Unless you have a deep understanding of the sky, generally you are going to need a map or planetarium software to find Neptune.
If you do not have the required software, Sky and Telescope regularly posts advice and maps helping you to find them.
Another thing to consider, is that from 2017 all the way up until 2024, Neptune is moving eastward from the constellation Aquarius into Pisces.
While it doesn’t typically attract much interest compared to the other and brighter planets in our solar system, Neptune is still observable with a telescope.
Despite being a distant ice giant and with therefore restraints on viewing the finer details, the subtle colors and fascinating satellites pose a great challenge to you.
Ultimately, you are going to need a telescope that provides you with high magnification and optimal resolution (long-focal length and Aperture).