Some telescopes are ideal for looking at ground based objects, but not so good at the sky, some telescopes are best for viewing deep sky objects, like galaxies and nebulae.
So finding the best telescope for viewing planets is not so straightforward.
Which telescopes offer the best all round performance for viewing planets?
The following Catadioptric telescope are the ones I would recommend.
The 3 Best Telescope For Viewing Planets
Two eyepieces are included, of 25mm and 10mm, and if you have a secure enough table, it’s a great item for the money, but to get the most from it, you may want to get a good quality tripod. A barlow lens would also be worth investing in.
Its high-quality, large-aperture optics will give you stunning images. Astronomy Magazine raves that this telescope’s optics and simple design bring a “new level of joy to simple observing.”
Going up in price a bit, the Orion Skyquest XT8 is a massive Dobsonian telescope, with a 1200mm focal length, and a big 8″ aperture.
Dobsonian telescope feature rock-solid mounts, and will last a lifetime, but can be more difficult to move around because of their sheer size. They are easily to upgrade, and again, a Barlow lens would be worth adding to this telescope.
How To Choose The Best Telescope For Viewing Planets
The first lesson to learn here is to ignore the advertised maximum magnification which you will often see on a telescope. Although you could theoretically magnify a planet by 500x with a fairly cheap telescope, the image would just be a blur, not worth looking at. What you want to know is the maximum practical magnification, and that is something entirely different.
As well as power not being everything, it is also not as important to get the maximum aperture size. When viewing deep space objects, the bigger the aperture, the better, as you are gathering as much light as possible.
But for viewing planets, it’s not so important, and in fact a very big aperture telescope, looking at a relatively close object like a planet, may suffer from too much atmospheric disturbance.
What is important is the focal length, and the best telescope for viewing planets will be the one with the combination of the longest focal length, and after that, the biggest aperture, all within your budget.
You also want a rock – solid tripod to hold your telescope as still as possible. Many expensive telescopes are not used to their full potential because images shake around too much, due to a flimsy tripod, or mount.
The eyepiece size is another important consideration.
Many telescope come with two or three eyepieces included, usually of 20mm, 10mm, and 4mm. The 20mm eyepiece will give you a wider field of view at lower magnification; the 4mm eyepiece will give you a very small field of view at a high magnification.
The function of an eyepiece is to gather as much light from the viewed body in order to create a clear image. The type of eyepiece one needs depends on the f-ratio of the telescope. For instance, an f/10 telescope does not require any particular eyepiece in order to create a good image but a f/4 will need a specific kind.
When looking for an eyepiece, keep in mind the eye relief, or the distance from your eye to the eyepiece lens, as it determines if you can see the entire field of view. Eyeglass wearers, especially, need to have at least a 15mm eye relief or the outer portion of the viewing field will be cut off. Traditionally the eye relief was directly related to the focal length, but newer eyepieces differ from that method.
The eyepiece also determines the field of view. An eyepiece’s apparent field is the angular diameter of the circle of light that the eye sees expressed in degrees. The apparent view, divided by the eyepiece’s magnification determines the eyepiece’s true field of view. The true field of an eyepiece is the actual amount of area which is seen when looking through the eyepiece that is attached to a telescope.
While magnification is not the most important aspect of choosing an eyepiece, it is something that needs to be considered. One needs to decide how much magnification they desire and the focal length that such an eyepiece will give them.
If one already knows what magnification they would like, they can figure out the eyepiece’s needed focal length by dividing the telescope’s focal length into it. Likewise the telescope’s focal length can be divided by the eyepiece’s focal length to determine the magnification.
The aperture of an eyepiece is the most important element. The aperture determines how much light will be taken into the eyepiece, and thus how clear the image will be.
The aperture for an eyepiece should be determined by the power per inch and the exit pupil size. The exit pupil is the number of light rays which leave the eyepiece.
The exit pupil of an eyepiece must be smaller than one’s pupil and is calculated by dividing the telescope’s aperture in millimeters by the magnification. Or it can be determined by dividing the eyepiece’s focal length in millimeters by the telescope’s f-ratio.
There are six different types of lenses which one can purchase. They are the Huygenian, Kellner, Orthoscopic, Plossl, Erfle, and Ultrawide. The Hygenian eyepiece is obsolete now, and has an extremely short eye relief and small apparent field.
The Kellner eyepiece is three-element and the least expensive lens appropriate for serious astronomers. The apparent field of a Kellner eyepiece is about 40 degrees and it provides sharp images at low to medium powers.
The Orthoscopic is four-element and once considered the best lens available. Though the newer lenses have minimized its appeal because of its narrow field. The four-element Plossl is the most popular lens as of late.
The apparent field of view for this eyepiece is 50 degrees and the image quality is excellent along with good eye relief. While the Plossl eyepiece was once considered a luxury lens, it is now more common.
The Erfle is 5 of 6 elements, and while it offers a wide apparent field of 60 or 70 degrees, the image sharpness suffers at the edges with high magnifications.
Ultrawides can be 7 or 8 element, and offer huge apparent fields (up to 85 degrees) which some people enjoy. The light transmission can be slightly diminished because of the numerous elements but the image quality is still fairly high. The Ultrawide eyepiece can have a very pricey tag however.
Adding a Barlow lens, which some telescopes include, can double or triple magnification, and if you do not get a Barlow lens with your basic kit, it is well worth investing in one.