[Leica] My Nikon 5 cm BL finder restoration

[vick.ko at sympatico.ca (Vick Ko)]

Wow, remember the days when being a photographer meant being a chemist, 
as you should do your own development?

Well, imagine if you also "made your own optics".

For those who don't know, I bought the housing of a Nikkor 5m Brightline 
finder.  Typically, this item is worth $2K if complete.  My finder was 
missing its entire front optics.

See these two ebay auctions to get an idea:
1.  Item number:190484845353 - my finder.
2.  fully kitted  - Item number:230567786121
    The seller is a m*ron - the kit might be worth $8K because it is 
complete.  This is the only time I've ever seen the complete kit.

So, trying to transplant lenses from other Nikkor and Leica brightline 
finders hasn't worked.  But, I now, after disassembling the Leica SBOOI, 
I now know the optical design of the Nikkor unit.  The beauty of the 
design is that it is just plano windows, except for the mirrored surface 
that projects the brightlines.  And so obvious that it should be plano, 
as the finder is 1:1 magnfication - no lensing is done !

And, for the shear fun of it, I've been modifying an SBOOI optical head 
to fit the Nikkor (as I await other finders to try; their "in the 
mail").  And, I am trying to achieve this "at home".

  I cut 3 mm off the flat end of the SBOOI optical head, with a tungsten 
hacksaw blade.  I was amazed that it worked at all.  I'm now trying to 
repolish the optical flat onto the prism.

Now, this is, and isn't, black magic.  There is a history of home 
telescope making.  Just that I've never done it.  And it is ironic that 
I used to work at Leitz Midland, where there were entire shop floors 
dedicated to polishing prisms.  I'm trying to repolish the flat, in my 
kitchen (thank god my family has "gone away" this weekend).

So, what are my findings?

-this is fun.  And you learn a lot
- hardware stores have far too few neat stuff.  Can only get emery paper 
to 440.  Need much finer.
- why don't people make things any more?  Ottawa has a telescope store 
(Focus Scientific), but only deal with "ready made".  What happen to 
those, that appreciate the joy of making your own mirror and telescope?
- trial and error can be frustrating.
- I can get the prism flat (but with oh so horrible scratches)
- I can get better flat finishes, with fewer scratches
- I can't get a good polish yet.  Maybe I'm using the wrong compound 
(car polishing compound)
- I have cerium oxide "in the mail" - thank god for ebay and mail order

....Vick