Best Telescopes for Deep Space

Deep space refers to the distant edges of outer space. NASA tends to set this at a distance of between 16,000 and 32,000 kilometers from Earth’s surface.

The International Telecommunication Union states it starts at 2 million kilometers from the surface of the Earth.

While there is disagreement about where deep space begins, what can be agreed on is that it is very, very far away. 

Buyers Guide

Portability 

Often when you are attempting to find certain objects in the night sky, there are specific locations you need to go to to find them. These tend to be high vantage points, such as mountaintops. 

If you are to take your astronomy seriously, you will need a telescope that can be broken down and compacted for ease of transportation. 

Mount design

There are 3 main designs for mounts: Dobsonian, Altitude-Azimuth, and German-Equatorial mounts. 

Dobsonian mounts tend to be preferred by most users of large aperture telescopes. They do not track the sky, and instead, you must move the telescope in line with the motion of the celestial object.

As technology advances, Dobsonian telescopes are more commonly becoming able to track the sky and perform GOTO functions. 

Dobsonian mounts are a subcategory of Altitude-Azimuth mounts. These tend to be lighter and more compact than equatorial mounts. You must move 2 different parts of the mount at once to adjust the position of the telescope.

Equatorial mounts are much heavier than Altitude-Azimuth. You must have weights on it to counterbalance the weight of the telescope. 

Optical design

Newtonian Reflectors are the best kind for deep space viewing. This will often give you the largest price : aperture ratio. Pay attention to the focal length with this design. It can be difficult to reach the eyepiece or angle the telescope.

Schmidt-Cassegrain telescopes are less affordable than Newtonian but are still popular choices. They also have long focal lengths, but you may need a reducer or corrector to increase your field of view.

Aperture 

This refers to the diameter of the lens (or mirror) in the scope. In other words, the diameter of the surface that the refracted light is collected on. In refractor telescopes, this is the diameter of the objective lens, and in reflecting, it is the diameter of the primary mirror. 

This is one instance where size does matter! In almost all cases, a larger aperture is better. This is because the larger aperture allows more light into the eyepiece.

This extra light improves the image quality, particularly if the objects are faint. This works to produce a finer and clearer image. The standard aperture of a telescope is at least 2.8 inches or 70mm. 

Eyepieces

These are made of many lenses contained within a metal cylinder. The numerical value of the focal length is written on the side. Lower focal lengths will help with increased magnification whereas higher focal lengths are better for a wider field of view.

Changing the eyepiece is the best way to play around with the magnification of your telescope. 

Focal length

The focal length is the distance between the focal point and the objective lens. Longer focal lengths create large but faint images and vice versa for shorter focal lengths.

The focal ratio can be calculated by dividing the focal length by the aperture (in mm). The lower the focal ratio (f-number) of the telescope, the better they are for viewing objects in deep space. A ratio of f/5 is usually good for looking into deep space. 

Magnification

This is determined by the eyepiece you are using and the focal length of the telescope. Magnification is very useful for enlarging clear images, but almost useless if your image is blurry.

We have written an article on how to calculate the magnification, which can be found here. 

Electronic control

Many telescopes will have a built-in computer that will help you to locate objects in the night sky. This means that you do not have to worry about using a star map to find specific constellations. 

This is not vital for most telescope users. It is only really useful if you wish to delve into astrophotography.

Type of telescope

Refractor

These are the oldest and most traditional types of telescope. They are also known as dioptric telescopes and were most common in the early nineteen hundreds. Technology has advanced a lot since then, and most other telescopes are better.

It is a straight cylindrical tube connected to an eyepiece. At the other end, a lens is placed and this is what allows you to view the image that is produced.

Reflector

This type of telescope was invented by Sir Isaac Newton and is also known as a catoptric telescope. It differs from a refracting telescope as it uses a series of curved mirrors to reflect light that bounces off objects far away. This forms an image at the eyepiece. 

The curved mirror is located on the edge of the cylindrical surface. This creates an image on the focal plane using light reflected from objects far away. This image can also be seen directly via the eyepiece. The Hubble telescope and many other modern telescopes use this technology.

Compound

This is also known as a catadioptric telescope. This uses 2 mirrors, situated at the front and back of the cylindrical tube.

They work in conjunction with the lens to create the image.

Image quality 

The image quality must be high if you want a clear and sharp image of the night sky. As technology has advanced, the image quality of telescopes has improved.

Every telescope has a limit to how far it can look. Once this point has been passed, something known as optical aberrations begin to occur. This is when an object in the sky appears to be displaced. This is caused by the relative motion of the celestial body and your position.

You should always check the limit of the telescope. This will prevent any disappointment in the future. 

Ease of use

This is an important consideration when purchasing a telescope. If it is not easy to assemble and use, you may be dissuaded from using it as often as you intended.

If you are purchasing the telescope for a child, they must be able to set it up and operate it by themselves. 

Base support

The type of base support you will need depends on the surface you plan to set the telescope up on. It is important to have a stable base for your telescope to ensure the image you see is clear. 

You can get table supports, floor supports, and tripod stands. These should be adjustable, allowing you to change the length of the stand. We recommend checking all the different ways you can set up your telescope before purchase. 

Finder

This is used to help you track the location of specific objects in the night sky. There are 3 main types: peep sight, reflect sight, and what is essentially a mini telescope. 

The peep sight is the easiest to use and is ideal for beginners. The reflect sight projects a red laser beam into the sky. The final option uses crosshairs to precisely pinpoint the location of whatever celestial object you are looking for. 

The aperture should be larger than 25mm (1 inch).

Accessories

These include things such as base supports, eyepieces, and Barlow lenses. The most vital are the base support and tripod stand, which are used to stabilize the telescope. 

A digital monitor is a great accessory to have. This will allow you to project the image from your telescope onto a screen. This can then be recorded and shared. 

User manual

Telescopes are complex pieces of equipment which are also incredibly delicate. They must be treated with care as they can break easily if assembled incorrectly or dropped.

This can be very stressful to do if you do not have prior knowledge of telescopes. The telescope should come with a detailed user manual complete with assembly and care instructions. 

Cost

The telescope technology is very advanced and this comes with a hefty price tag. The complexity of the internal detail of your telescope dictates the price tag and usually the quality too. 

You should look at your telescope as an investment. High quality models will last for years to come and you are likely to only buy one or two in your lifetime. 

Frequently Asked Questions

How do you properly clean a telescope?

You should use a camel hair brush to clean dust particles off of the telescope lens. These can commonly be found in camera stores. There are many cleaning solutions available that are suitable for using on the telescope lens. These tend to be methanol-based.

You should always keep the lens cap on the telescope when it is not in use. We also recommend pointing your scope towards the ground. This will stop dust from settling onto the optics. 

We suggest storing any extra eyepieces in a plastic bag. We do not recommend touching the lens or mirror inside your telescope.

How to improve your stargazing experience

You should begin by lowering your expectations. The images of the night sky that you see online are taken by the Hubble telescope and you will not be able to get images of the same clarity or quality. 

Try to avoid buildings and other large objects. This is because they emit heat at night and this can hinder your ability to see stars and planets due to the increased air currents. 

Do not attempt to view your telescope through a window. This will act as an additional lens and make the viewed image much less clear.

Begin your session using the lowest value eyepiece. Counter-intuitively, this is the one that has the largest number marked on the outside. These images will be brighter and sharper than higher value eyepieces.