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Mirror clips

Started by De Lorme, 12/15/2012 11:30AM
Posted 12/15/2012 11:30AM Opening Post
Hi, Deos anbody know where to buy mirror clips for an old Odessey 17.5 mirror? The mirror is 1.5" thick.
Iv'e looked at a few home made cell designs but is there a specific one for a large mirror that can be easily made? Thanks for your help. De Lorme
Posted 12/16/2012 12:51PM | Edited 12/16/2012 05:15PM #1
With any such clips, ALL they do (or Should do) is to keep the mirror from falling out if the scope were positioned horizontal, or worse, at a greater angle(upside down). These clips should Never apply direct force to the mirror itself lest deformation of the mirror's figure occur with detrimental effects on the image; IOW always loose-fitting. So, you should be able to fabricate clips from sheet-metal, wood, or plastic using ordinary home tools & a hand drill for screw holes. Even simple blocks of wood attached to the inside of the tube or mirror box above the mirror will provide this fall-out prevention function; they needn't be attached to the mirror support itself. Alternatively, don't tip your scope to horizontal (and eliminate diffraction-creating clips in the optical path). Apply self-stick felt furnaure pads (a local Hardware store item) to the mirror-side of such clips to avoid scratching the mirror coating in the event the mirror does contact the clips. IOW you do not need mfg-specific clips for this purpose & making such clips for an already at hand mirror support is far simpler than making an entire support which also requires clip fabrication. For transport, a secured full mirror cover will protect against fall-out & protect the mirror surface as well = better than clips for this purpose.
Posted 12/16/2012 07:41PM | Edited 12/17/2012 07:02AM #2
For any size mirror, the simplest & easiest to construct is an over-sized flat triangle of wood under the mirror. The cut-off *points* of the triangle are the mounting points & can be supported parallel to the optical axis by bolts & nuts (like *legs* protruding behind & attched to rear of mirror box). Springs over the bolts under the board work well with smaller mirrors or nuts on each side of board with bolt passing thru allows mechanical push-pull alignment that remains aligned when screwed down snug despite travel vibration (use washers under the nuts to spread load across more wood). Anchor the bolts to either the mirror box or cell board with adjustment provided at the other ends of bolts; which end depends on what is convenient to your situation/arrangement. Size the wood thickness & bolts to the mirror; if they look flimsy they are & likewise if they look sturdy enough. An index mark on the mirrors' side (or back, if view holes are cut into mirror board & mirror box) along with a corresponding mark on the cell allows returning to collimated position if travel rotates the mirror in it's cell. Heavy-duty felt furnature pads may be used to support the mirror (underneath) & inverted L-shaped blocks of wood standing on the *point* ends serve as both retaining clip & side supports (padded with pieces of furnature pads). Precision construction is un-neccessary since the mirror should Not be clamped tight to cell, but remain loose-fitting. The larger the mirror, the more underneath support pads used. I used such a home-made push-pull cell for decades & never needed to re-collimate unless the mirror was removed.