How do I check for scratches on the surface of the coatings? When I tried the flashlight test on my meade sct UHTC optics, I found MANY, MANY surface scratchmarks that I didn't make. Also, when the corrector fogs up, they appear.
scratch marks on corrector surface
Started by acgtek, 12/06/2003 06:40PM
Posted 12/06/2003 06:40PM
Opening Post
Posted 12/06/2003 07:01PM
#1
Argh!!! The dreaded "flashlight test" strikes again!
Problem with the flashlight test is that it
has no calibration and is far too sensitive.
If you thought of sticking the flashlight against
your eye as "1" and then thought about the
(hopefully) faint little scratches, one realizes
there is actually very little light involved
with the scratches ... maybe 0.001 or 0.1% of
the light (or at least I hope thats the
case for your corrector).
Better test is too point the scope at an illuminated
blank wall, take out the eyepiece, and look in the
back. If you can't see the scratches from back there,
I wouldn't worry about it. This method does provide
some calibration (the illuminated wall).
All optical surfaces have some amount of imperfections
(unless you get laser-grade optics for 10 times
more $). So long they don't show up at the
back end of the scope, you should be OK.
Problem with the flashlight test is that it
has no calibration and is far too sensitive.
If you thought of sticking the flashlight against
your eye as "1" and then thought about the
(hopefully) faint little scratches, one realizes
there is actually very little light involved
with the scratches ... maybe 0.001 or 0.1% of
the light (or at least I hope thats the
case for your corrector).
Better test is too point the scope at an illuminated
blank wall, take out the eyepiece, and look in the
back. If you can't see the scratches from back there,
I wouldn't worry about it. This method does provide
some calibration (the illuminated wall).
All optical surfaces have some amount of imperfections
(unless you get laser-grade optics for 10 times
more $). So long they don't show up at the
back end of the scope, you should be OK.
Funding Member
