8″ (Eight Inch) T.D.E. “Turned Down Edge” Ring / Mask Improves Primary Mirrors – Sharpening Rings, Mirror Clip Mask for Reflector Telescopes


Fix a turned down edge, stop mirror clips from affecting your imaging etc.. by installing a TDE Ring / Mirror Clip Mask.

Easy to understand instructions, illustrated.


CNC Laser Machined, Flat Black Sharpening Mask

During the mirror grinding process and figuring, it is very common for mirrors to have a “Turned Down Edge” or a larger “Rolled Edge” (which is more severe).  This causes the image to deteriorate and look “fuzzy” at the eyepiece, have a “soft edge” or there is a “hairy” edge inside focus.

A tried and tested solution is to install a “TDE” Mask, or “Sharpening Ring”, which simple makes the undesirable part of a mirror (in this case, the outer edge) unable to affect the image.

Astro Dog’s TDE Sharpening Masks are highly accurate, laser cut, flat black on both sides and are made of good quality quality thick 3mm Acrylic right here in Australia.

What you will get

1 x 8″ TDE Ring

Specifications : 203.2mm diameter – ID : 196.85 / OD : 222.25


  1. Remove the screws from the bottom of your tube
  2. We recommend installing a tape, then cutting it so you can clearly see the way to put the tube back.
  3. The rings will sometimes cover the mirror clips also, if not, you may be able to shorten the clips slightly by trimming the rubber slightly.  Keep in mind, doing so may mean that the mirror is at increased risk of being dislodged and is at your own risk.
  4. Put a small blob of silicone or similar next to the cut hole.
  5. Install on top of the mirror clip.  You can use something like kilometrico pen caps between the top of the rubber mirror clip and the mask to keep the distance the same.
  6. Adjust the ring so it is exactly even.
  7. Done!



Additional information

Weight .5 kg
Dimensions 28 × 18 × 10 cm


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