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Dobsonian Mounts
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Standard Solid.
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Mount stands to raise height.
Mirror Cells and
Image Sharpening
Mirror Masks for TDE.
Remove Mirror Clip Diffraction.
Aperture and Solar Masks.
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Altitude Bearing Selections.
Teflon.
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Clamshell Rings for EQ Heads.
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Mirror Masks


Prototype 10" mirror mask.


Drawing details.

Mirror Masks
$20.00 In stock.

Mirror masks can help improve telescope performance by correcting for Turned Down Edge (TDE). If you would like a mirror mask that aslo eliminates diffraction anomolies induced by mirror clip overhang, we can create a custom design for you.

Masks reduce mirror size by 1/2" while negligably reducing limiting magnitude as shown here.

Constructed of 1/8" thick black acrylic, masks are stiff, light weight and have a non-reflective matte side. Slots are cut that allow you to center the mask on the mirror's edges. Small notches provide a mark for locating the mask on top of mirror clips. Attaching them with any adhesive such as Velcro dots.

Mirror Size
Mask Inside Diameter
Mask Outside Diameter
6.0"
5.5"
7.0"
8.0"
7.5"
9.0"
10.0"
9.5"
11.0"
12.0"
11.5"
13.0"
12.5"
12.0"
13.5"

Order
$20 each. 
Mirror Size
Ph# for shipping documents
Shipping $6 in CONUS for up to two masks.
We will send you a separate PayPal shipping invoice.

Detail of flat black and gloss sides.

12" and 6" masks shown.
Turned Down Edge

Authoritative optical tester Dick Suiter discusses masking mirrors (see #2) to improve image quality.

"Turned down edge (TDE) Outside of proper parabolization, edge problems are the most common maladies afflicting mirrors. A turned down edge, or TDE, is a narrow zone, no more than 1/8 inch [3mm], at the extreme edge that turns downward, focusing long. If the zone is wider then it is called a rolled edge. Rarely the extreme edge will turn upward, focusing short. This is called a turned up edge." - Mel Bartels