Turned Down Edge

Hello all!

How do TDE show up in a Newtonian scope? I mean at actual observing at high power.The out of focus patterns are well known;sharp diffraction rings out of focus and fuzzy, almost washed out inside focus.

-Magnus

I recall encountering an 8 or 10" newt whose primary had a known bad TDE.
The owner had a removable edge mask and could demonstrate the TDE by
removing the mask. With the mask present, you could discern an appropriately
picked faint target near a brighter object. Remove the mask and it became
significantly more difficult. With the mask in place, the scope performed
nicely, just with a reduced aperture. With the mask gone, it was not unlike
a fairly dusty mirror.

Dan

Everything will have a faint but broad halo.
It can be difficult to see, since it will
smoothly fade to nothing, and be similar to
scattering in the eye or slight atmospheric haze.