Meade ETX-105EC, ETX-125EC Observation Techniques, Choosing an Eyepiece, Alignment

2.Point the main telescope at some easy-to-find, well-defined land object, such as the top of a telephone pole. Center the object, as precisely as possible, in the SP 26mm eyepiece's field of view, then tighten the vertical and horizontal locks (6 and 9, Fig. 1) so that the tube cannot move and the object remains centered (1, Fig. 7).

3.While looking through the viewfinder, turn one or more of the three front viewfinder alignment screws (4, Fig. 6), until the crosshairs of the view- finder point at precisely the same position as the view through the eyepiece of the main telescope (2, Fig. 7).

	(before
	alignment)
	1
View through the	View through the
viewfinder	telescope eyepiece
	(after
	alignment)
	2

Check that the viewfinder’s crosshairs
	Fig. 7: Aligning the Viewfinder.
and the main telescope are now pointing

at precisely the same object. The viewfinder is now aligned to the main telescope. Unless the alignment screws are disturbed or the viewfinder jarred, the viewfinder should remain aligned indefinitely.

Tip: If you plan on viewing using higher magnification eyepieces, first locate, center, and focus the object using a low-power eyepiece (e.g., SP 26mm eyepiece). Then remove the low-power eyepiece and replace it with a higher-power eyepiece; the object should still be centered in the field of view. Objects are much easier to locate and center at lower powers; higher powers are employed simply by changing eyepieces.

OBSERVATION TECHNIQUES

The ETX model telescopes can be used for immediate observation right out of the box. However, becoming familiar with the fundamentals of a telescope makes subsequent viewing easier and more rewarding.

Choosing an Eyepiece

A telescope’s eyepiece magnifies the image formed by the telescope’s main optics. Each eyepiece has a focal length, expressed in millimeters, or “mm.” The smaller the focal length, the higher the magnification. For example, an eyepiece with a focal length of 9mm has a higher magnification than an eyepiece with a focal length of 26mm.

The SP 26mm eyepiece, supplied with your telescope, gives a wide, comfortable field of view with high image resolution, while an optional SP 12.4mm eyepiece, for example, provides a smaller field of view but higher magnification when seeing conditions permit.

Low-power eyepieces offer a wide field of view, bright, high-contrast images, and less eyestrain during long observing sessions. To find an object with a telescope, always start with a low-power eyepiece such as the SP 26mm. When the object is located and centered in the eyepiece, you may wish to switch to a higher-power eyepiece to enlarge the image as much as practical for prevailing seeing conditions.

Note: Seeing conditions vary widely from night-to-night and from site-to-site. Turbulence in the air, even on an apparently clear night, can distort images. If an image appears fuzzy and ill-defined, back off to a lower-power eyepiece for a more well-resolved image (Fig. 8a and 7b).

TIPS FOR BEGINNERS

Too Much Power?

Can you ever have too much power? If the type of power you’re referring to is eyepiece magnification, yes, you can! The most common mistake of the beginning observer is to “overpower” his or her telescope by using high magnifications which the telescope’s aperture and atmospheric conditions cannot reasonably support. Keep in mind that a smaller, but bright and well-resolved image is far superior to one that is larger, but dim and poorly resolved (see below). Powers above 300X should be employed only under the steadiest atmospheric conditions.

Most observers should have three or four additional eyepieces to achieve the full range of reasonable magnifications possible with the ETX telescopes. See OPTIONAL ACCESSORIES, page 20.

Fig. 8a & b: Jupiter; example of too much magnification.

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