How to Use This Calculator
- Enter your telescope's aperture in millimeters (mm). This is typically found in your telescope's specifications.
- Input your telescope's focal length in millimeters (mm). This is also usually listed in your telescope's specifications.
- Enter the focal length of your eyepiece in millimeters (mm). This value determines the magnification.
- Click the "Calculate" button to see your telescope's current magnification and its maximum practical magnification.
Understanding Telescope Magnification
Magnification is calculated by dividing the telescope's focal length by the eyepiece's focal length. Higher magnification allows you to see finer details, but only up to a practical limit.
Maximum Practical Magnification
The maximum practical magnification is determined by your telescope's aperture. A general rule of thumb is that the maximum useful magnification is about 2x per millimeter of aperture. Using magnification beyond this limit will typically result in a blurry, dim image that offers little additional detail.
Tips for Using Your Telescope
- Start with lower magnification when observing objects like the Moon, planets, or star clusters.
- Higher magnifications work best for observing the Moon and planets, but be prepared to reduce magnification if the image becomes too faint or blurry.
- Consider atmospheric conditions - on nights with poor seeing conditions, reduce your magnification.
- Never push your telescope beyond its maximum practical magnification, even if your equipment allows it.