Fixing a Loose Secondary Holder

Occasionally secondary holders will become loose and rotate freely. That's not good. Like the corrector, the secondary mirror needs to be in a particular rotational position for optical performance. It's easy to fix this problem with recent telescopes. The secondary mount is a two-piece assembly held in place by the conical baffle surrounding the secondary mirror on the inside surface. The baffle screws onto the secondary mount, sandwiching it to the corrector. Remove the corrector plate as above, and, grasping the outer surface of the secondary mirror, mount with one hand and tighten the baffle, making sure the secondary mount remains in the correct orientation. Unfortunately, some Celestron OTAs—mostly earlier ones—have secondary assemblies that are glued in addition to being screwed together. In these cases, it's probably best to consult the manufacturer.

What is the correct secondary holder orientation? On a Celestron fork mount scope, the word "Celestron" printed on the secondary holder should be right-side-up, with the tube level, and will line up with the serial number on the corrector. Some scopes may not have "Celestron" on the secondary, but there will almost always be a serial number. On a Celestron GEM OTA oriented so the focus control is level and on the right, "Celestron" will, again, be right-side-up. Meades usually do not have words or serial numbers on their secondary holders. Assuming the secondary mount hasn't rotated too far, orienting it so that the triangle formed by the three collima-tion screws has its apex pointing up will (usually) yield the correct orientation. If in doubt, you can mark the back of the secondary mirror 's backing plate. The mirror can be removed from the holder in order to examine it by unscrewing all three col-limation screws, but most users stop there and just call Meade.

Mirror cleaning? It can be done in a pinch. The best tool is a soft brush. The brush on a Lenspen will work (don't use the cleaning tip). A clean camel's hair brush is even better. If more than dusting is required, use the Meade cleaning fluid recipe. Work the same way as when cleaning a corrector, but use USP cotton balls purchased at a pharmacy rather than lens tissues. Do not apply any pressure to the fluid-wet cotton; just drag it across the primary's surface, changing cotton balls frequently and dabbing the mirror dry with clean ones when done. It's best not to try to remove the primary for cleaning; work with it in place, taking care not to spill excess lens fluid into the rear cell assembly. Again, it's almost always best to leave both mirrors strictly alone and call Meade or Celestron.

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