Fix Turned Down
Edge (TDE)
Mirror
masks can help improve telescope performance by correcting for Turned
Down Edge (TDE). If you would like a mask that
also eliminates diffraction anomalies
induced by mirror clip overhang, or have a different diameter
mirror, we can create a custom design for you. For example, a customer
asked writing: "The star test shows that my new GSO Dobson has
some TDE. GSO uses metric dimensions and the diameter of the mirror
is 200 mm not 8 in (203 mm)."
If your mirror has TDE, masking the outer 1/8" (where TDE usually
occurs reduces your theoretical limiting magnitude but assures a sharper
image:
| |
Limiting
magnitude
|
|
Mirror
diameter
|
Without
mask
|
With
mask
|
|
6.0"
|
13.61
|
13.43
|
|
8.0"
|
14.24
|
14.10
|
|
10.0"
|
14.72
|
14.61
|
|
12.0"
|
15.12
|
15.03
|
Constructed
of 1/8" thick black acrylic, masks are stiff, light weight and
have a non-reflective matte side. 0.25" holes 120 degrees apart
allow you to precisely center the mask at the mirror edge. Attach using
small Velcro dots on top of mirror clips.
