From: "Bob Walker" 
To: "ATM Group" 
Reply-To: "Bob Walker" 


I tried a new method of strain testing on my brand-new secondary.  Dropped
it 4' onto concrete.  The resulting chips out of the edge are perfectly
semicircular, so no strain, right?  The reason for the drop might prove
instructive.  Most of you probably know that silicone glue ages once the
tube is opened, and after a long enough time it won't harden, even though
it remains flowable in the tube.  When it reaches this stage, it usually
has a semi-granular texture, sort of like tapioca pudding.  What I just
found out the hard way is that it can look quite normal and still refuse to
harden. So, the moral of this story is, when gluing something really
important, like a mirror to its cell, don't use an old tube of silicone. 
Splurge.  Blow three bucks on a new tube.
All in all, a cheap lesson.  At least it didn't fall six feet onto my
primary!  ...speaking of which,  my first scope project, underway for over
a year now, is in usable form, though not finished.  An uncoated 16"
f/5.4 mirror works just fine for viewing Mars.  I can see more detail than
with my 8" SCT even with the chipped secondary and collimation only a
vague theoretical concept.  Much refinement to follow!

 *  Best regards, Bob
*
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