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I've heard that using a refractor is better than a reflector when it comes to planets to best reproduce their colors. But perhaps other factors can weight in too? For example, do you want a slow or fast f-stop to get the best view of a planet? What about eye-pieces, what style of eyepiece construction will give the best views?

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The two factors to consider in a telescope used to observe the planets are resolution and contrast. To get good enough resolution you need an aperture of at least 5 inches. In addition, the optics must be of high quality to deliver the most contrast. Despite the common recommendation of refractors, very few serious planetary observers use them, except for those able to afford large apochromatic refractors, which are very expensive. The typical amateur refractor is too small in aperture to show much on the planets. Telescopes using the Maksutov design work very well, but also become expensive and heavy in larger sizes. So, most serious planetary observers use Newtonian reflectors. Traditionally long focal ratios (f/6 or longer) perform the best, but modern short focal ratio (f/4 or f/5) mirrors can perform almost as well, so long as their optical quality is high.

In general, simple eyepieces of older design (orthoscopic, Plössl) are best because of their high contrast, but typically they have very short eye relief, so that many observers prefer more modern designs with longer eye relief, such as Tele Vue Radians.

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