What counts as deep space?
In amateur astronomy, “deep space” or “deep sky” usually means objects beyond our solar system: star clusters, nebulae and galaxies. They are faint, so the best telescope for them is generally the one with the most aperture that you can realistically transport, set up and use under reasonably dark skies.
Aperture and dark skies come first
Light-gathering power grows with the area of the mirror or lens. Doubling the aperture gathers about four times the light. That is why large Dobsonians are so often recommended for deep-sky observing.
Sky darkness matters just as much. A moderate scope under a dark sky can beat a large one in a bright suburb. If you can reach a dark site, even occasionally, you will see far more. Consider using a map of light pollution to find one, and see our dark-sky camping guide for planning a night out.
Best types of telescope for deep space
Dobsonian reflectors
A Newtonian reflector on a Dobsonian mount provides the most aperture per dollar and is easy to use. An 8-inch model is a very common recommendation, and 10-inch and 12-inch versions show more of the faint detail at the cost of size and weight. Collapsible truss designs are easier to transport. See our guide to picking a good telescope for how Dobsonians compare with other designs.
Schmidt-Cassegrain telescopes
Compact SCTs, often on computerized mounts, give a lot of aperture in a short tube. An 8-inch model is a popular all-rounder for both planets and deep-sky objects, and the GoTo mount helps find targets. They cost more per inch than Dobsonians. See best GoTo telescopes.
Wide-field refractors
Small, fast refractors give wide views suited to large objects such as the Andromeda Galaxy, the Pleiades and big nebulae. They are also popular with astrophotographers.
Smart telescopes
Smart telescopes stack many short exposures and show a growing image on a screen. They reveal color and detail in nebulae and galaxies that you would not see by eye in a small scope, and they are easy to use. The trade-off is that you are viewing a processed image rather than looking through an eyepiece.
What will galaxies and nebulae look like?
Visually, most deep-sky objects appear as faint gray patches. Bright ones such as the Orion Nebula and the Andromeda Galaxy are impressive even in small scopes, but spiral arms and color are usually subtle or invisible to the eye. Photographs and live-stacking reveal far more. Setting that expectation early avoids disappointment; what it looks like through a telescope gives realistic expectations.
What telescope do I need to see galaxies?
A 6 to 8 inch scope will show the brighter galaxies from a reasonably dark site. Larger apertures reveal more of their structure.
What is the best telescope to see everything?
No single telescope does everything. A mid-size Dobsonian is a good all-round visual choice, while imaging requires different gear.
What telescope can see the farthest?
Professional observatories and space telescopes see the farthest. Among consumer telescopes, larger aperture and darker skies let you reach fainter and more distant objects, but there is no simple distance figure you can rely on.
Useful accessories
- A low-power wide-field eyepiece
- A nebula or light-pollution filter, which helps with some nebulae, though results vary by object and sky
- A red flashlight and star charts or an app
- A comfortable observing chair
Planets or deep space?
If your interest is mostly planets, a different scope may suit you better. See best telescopes for looking at planets. On a tighter budget, see best telescope for watching stars and how much a good telescope costs.
Seeing more in practice
- Allow your eyes to dark-adapt for at least 20 minutes.
- Use averted vision, looking slightly to the side, to see faint detail.
- Observe objects when they are high in the sky.
- Avoid nights with a bright Moon for faint objects.
- Let the telescope reach outdoor temperature first.