While small telescopes can show a lot of objects, they may only be seen as colorless dots or smudges. Size does matter in astronomy–bigger is better in many cases.
The larger the lens or mirror diameter or aperture,
While small telescopes can show a lot of objects, they may only be seen as colorless dots or smudges. Size does matter in astronomy–bigger is better in many cases.
The larger the lens or mirror diameter or aperture, the more light your scope gathers and the higher resolution (ability to see fine detail) it has. Larger scopes also have longer focal lengths, meaning greater magnifications and image sizes are possible with both the eye and camera. Faint objects like nebulae and galaxies demand large aperture scopes. Planets need longer focal lengths for higher magnification views and large apertures for high resolution.
Nonetheless, here are some recommendations for specific scopes versus specific types of astronomical objects and observing:
- The Sun: A small scope properly equipped with a full-aperture solar filter will provide very good views of the Sun under typical daytime seeing (atmospheric steadiness) conditions. A moderate focal length will reveal granulations and sunspot details with your eyepieces. Apertures of 6 inches (150 mm) or less and focal lengths of 1000 to 1500 mm are good for looking at our closest star.
- Planets: Here you’ll need a long focal length scope to take advantage of high magnifications (when the atmosphere is steady enough to use them) to see details in Jupiter’s clouds, Mars’ features, etc. Large aperture is also great for high resolution when using with high magnifications. Therefore, the bigger the scope, the better to take advantage of good seeing for planetary viewing. Big scopes will also let you see faint Pluto, planetary satellites and minor planets. The best scopes are at least 5 inches (125 mm) aperture and 1250 mm focal length or more.
- Open Clusters: Except for the very biggest and brightest star clusters (Pleiades, Hyades, Beehive, Coma Cluster, etc.), you will need as large an aperture as possible and moderate to long focal length as well for the most interesting and sta