Why can’t I see anything using my eyepiece?
October 6, 2008
If you can’t see anything clearly through your telescope using your eyepiece, try using a different eyepiece; switch from a high-power eyepiece to a lower-power (ex: 4mm to a 20mm eyepiece) instead.
Always start with the lowest power eyepiece (the one with the highest number in millimeters printed on it). It is much easier to focus and has a wider field of view making it easier to aim the telescope. Look through the eyepiece by placing your eye just behind it, not right against the lens. Now turn one of the two knobs to the side or below the draw-tube–first one way then the other until the object is in focus.
Even with a lower-power eyepiece like the 20mm, a view can be blurry because of the Earth’s atmosphere. Heat waves and high-altitude winds move air around and cause differing temperatures of air to mix. This makes the air act like a weak lens that interferes with the light from a planet or a star by de-focusing it. On nights that are like this, the situation gets worse when you magnify it using an even higher power eyepiece like your 4mm.
Why do planets appear as small dots with Low-Power Eyepieces?
Planets are small and far enough away that they will never fill a significant portion of your field-of-view, even at you scope's highest usable magnification.
If you want to see a larger disk, you need to use a higher power eyepiece. Remember that the smaller the focal length eyepiece you use, the higher the magnification you will see in the scope.
For example, many of Celestron’s basic telescopes come with a 10mm eyepiece as the shortest focal length in the box with the new scope. Using a 5mm eyepiece instead will double the magnification compared with the 10mm eyepiece. Your scope will show a larger disk than what you are seeing now. It will still be a small disk, but you will potentially be able to see more detail than with the provided eyepieces.