Useful Telescope Magnification
About Useful Telescope Magnification
When looking at the magnification of telescopes you will come across a small number of ads that talk about extremely high telescope magnification that their scopes can achieve. These types of telescopes will often have around 60mm diameter apertures, and offer magnifications of 600x or higher.
It's true that images can be magnified to that extent, but what they actually wind up magnifying is all the air turbulence in between the telescope and the object being viewed.
Whenever you are taking a look at astronomical objects, you're looking through a vast column of air that stretches to the very edge of space, and that column rarely ever stays still. In a similar fashion, when viewing over land you are frequently looking through waves of heated air which is radiating from the ground, houses and other buildings.
A good general guideline is that magnification of a telescope that is actually usable is approximately 50x per inch (2x per mm) of aperture under good conditions.
Values of 3x per millimeter or higher are sometimes quoted for ideal conditions, however these conditions are very rare. The ultimate resolution that an astronomical telescope is capable of will depend on the amount of light that it can gather.
The larger the aperture, the higher the resolution and as a result the image is far better. Having said that, there are occasions when the earth's atmosphere is so unsettled that a smaller aperture will deliver far better results as it sees fewer turbulent zones.
A simple telescope cap with a modest opening which behaves as a mask, can turn out to be a handy add-on under these kinds of conditions.
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