Meade 4504 instruction manual Star testing the collimation

Star testing the collimation

With the collimation performed, you will want to test the accuracy of the alignment on a star. Use the H 25mm eyepiece and point the telescope at a moderately bright (sec- ond or third magnitude) star, then center the star image in the telescope’s field-of-view. With the star centered, follow the method below:

•Bring the star image slowly out of focus until one or more rings are visible around the central disc. If the collimation was performed correctly, the central star disk and rings will be concentric circles, with a dark spot dead center within the out-of-focus star disk (this is the shadow of the secondary mirror), as shown in C, Fig. 29. (An improperly aligned telescope will reveal elongated circles (A, Fig. 29), with an off- center dark shadow.)

•If the out-of-focus star disk appears elongated (B, Fig. 29), you will need to adjust the primary mirror Phillips-head tilt screws of the primary mirror cell (3, Fig. 24).

•To adjust the primary mirror tilt screws (3, Fig. 24), first unscrew several turns the three hex-head primary mirror cell locking screws (2, Fig. 24), to allow free turning movement of the tilt knobs.

•As you make adjustments to the primary mirror tilt screws (3, Fig. 24), you will notice that the out-of-focus star disk image will move across the eyepiece field. Choose one of the three primary mirror tilt screws that will move the star disk image to the center of the eyepiece field.

•Repeat this process as many times as necessary until the out-of-focus star disk appears as in C, Fig. 29, when the star disk image is in the center of the eyepiece field.

•With the star testing of the collimation complete, tighten the three hex-head primary mirror locking screws (2, Fig. 24).

ABC

Fig. 29: Collimation.

page 36