Meade LXD75 b c d e f g, b The four collimation screws on the diagonal mirror housing

Tip:

A useful tool for making collimation easier is to make a hole in the plastic cap that comes with the eyepiece to protect it during shipping. Use a drill to make a 1/8" hole in the center of the cap and place it over the eye- piece holder for use during the collimation procedure.

b Focuser drawtube c Diagonal mirror

d Reflection of primary mirror

e Reflection of secondary mirror (darkened due to back lighting)

f Primary mirror clips

g Reflection of observer's eye

Fig. 31b: The four collimation screws on the diagonal mirror housing.

knurled knob

thumb screw

Fig. 31c: The six collimation screws on the rear of the primary mirror cell.

b c d e f g

Fig. 31a: The view you will see while collimating a Schmidt-Newtonian telescope.

shipment of your telescope. It is only necessary for you to confirm that the telescope has not been badly jarred out of collimation, and to perform the final fine-tuning of Step 4, below.

Fig. 31a shows a correctly collimated Schmidt-Newtonian telescope, as it appears when viewed through the focuser with the eyepiece removed.

To check and, if necessary, set the optical collimation, follow these steps.

1.Observe through the focuser and orient your body so that the telescope's primary mirror is to your right, and the correcting plate end of the telescope tube is to your left. The diagonal mirror will appear centered as shown (2, Fig. 31a). If the diagonal appears off center, then adjust the 4 collimation screws on the plastic diagonal mirror housing.

2.If the reflection of the primary mirror (3, Fig. 31a) is not centered on the surface of the diagonal mirror, adjust the 4 collimation screws on the plastic diagonal mirror housing to center the reflection.

As described above, the 4 collimation screws (Fig. 31b) on the plastic diagonal mirror housing are used for two different adjustments during the collimation procedure.

Important Note: Do not force the 4 screws past their normal travel, and do not rotate any screw or screws more than 2 full turns in a counter- clockwise direction (i.e., not more than 2 full turns in their "loosening" direction), or else the diagonal mirror may become loosened from its support. Note that the diagonal mirror collimation adjustments are very sensitive: generally turning a collimation screw 1/2-turn will have a dra- matic effect on collimation.

3.If the reflection of the diagonal mirror is not centered within the reflection of the pri- mary mirror, adjust the 3 collimation screws located on the rear of the primary mirror cell.

Note: There are 6 screws (Fig. 31c) on the primary mirror cell. The 3 knurled knobs are the collimation screws, and the 3 smaller thumb screws are locking screws. The locking screws must be loosened slightly in order to adjust the collimation screws.

Proceed by "trial and error" until you develop a feel for which collimation screw to turn in order to change the image in any given way.

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