Re: Lenses Are On Order

[Chris Albertson <chrisja@jps.net>]

Tom Droege wrote:
> 
> The subject says it.  I have grabbed the Tiger by
> the tail, and we are now in for a ride with our very
> own optics.  Let's hope it is a good decision.  40
> lens sets are on order.  

I don't know if you got my comments about this or not.
I used an untested e-mail setup.

First off this is good but unexpected news.  I thought
you'd go with camera lenses at first.

My comment was that these lenses will need frequent cleaning.
The 135mm lens I have now was in need of cleaning as it had
more dirt on the fron element then I'd like.  I now have a
52mm "super multicoated" clear "filter" that will make normal
cleaning easy as it can be removed and placed under running
water to clean or at $20.00 replaced if damaged.  At my location 
cleaning is required about weekly.  After a month you can 
write with your finger in the dirt.

The reason I bring this up is that I have seen what frequent
cleaning can do to a muticoated optical surface.  It wears the
coating off at best or scratches it at worst.  There are two
easy solutions (1) cut threads in the lens barel to allow
installation of a protective filter.
The Mk IV would require a 125mm filter (I think.)  A good one
costs just under $100.00  or (2) Tell the coating designer to
use something very hard as the last coating layer even if it
compromises the optical design.  Operators can be carful but
"dirt happens". 


-- 
   --Chris Albertson             home: chrisja@jps.net        
     Redondo Beach, California   work: chris@topdog.logicon.com