Hi Bob,
You want to get something along the lines of ebay item 272331719376 or 
262202931320.  The boom is pretty important, otherwise how do you get your 
boards under the microscope if they're not very small?  Some time ago, I got a 
Bausch & Lomb Stereo 3 with 10X oculars and a 0.5 barlow.  The zoom scale on 
the scope reads 0.7 to 3.  This, combined with the 10X oculars gives it a zoom 
range of 7X to 30X.  This is a bit strong for doing PCB work, so the 0.5 barlow 
cuts that in half to 3.5X to 15X which is just about right.  I leave the boom 
at the right height to do soldering on the bench, but don't have the lateral 
thumbscrew on the boom tightened, so I can move the scope left and right or out 
of the way.  I wouldn't pay extra for a fancy light system like you'll see on 
many auctions.  Instead, I bought an LED light ring to go around the barlow 
lens on the bottom.  It has a brightness control, so it works out well.

As far as the board suppliers, I tried ExpressPCB at first, but they're pretty 
expensive, and you're stuck with their board size.  So, I switched to 
OshPark.com.  They don't supply proprietary board design software, which is 
fine, because there is a free version of Eagle, or you can use Kicad like I do. 
 (Kicad can output Gerber files.)  I believe that both Mouser and DigiKey have 
free board design software, as well.  But, the risk with those is that they 
either go away or become pay systems.
Bob - AE6RV
 -----------------------------------------------------------------
AE6RV.com

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      From: Bob Albert via time-nuts <time-nuts@febo.com>
 To: Discussion of precise time and frequency measurement <time-nuts@febo.com> 
 Sent: Thursday, August 11, 2016 12:24 PM
 Subject: Re: [time-nuts] Working with SMT parts.
   
What are the important parameters regarding purchase of a stereo microscope?  I 
see some on ebay for around $50; are those good?
Bob
 

  
  
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