[ATM] Ross null test - would this surplus shed lens work?

[Mark Cowan]

Hi Gil:

Do what Ric recommends re. the FL - it's a little long
for the size...maybe.  As to the material, there's no
problem with fused silica - just use the proper
refractive index in the position calculation.  And
post your results, it sounds like that could be a
really nice lens for a Ross Null setup...

Best,
Mark Cowan
Salem, OR

--- Gil McFarlane <gilboastro at yahoo.com> wrote:

> I would like to try the Ross null test - but
> spending
> $500 for a lens is out of my budget.  I found this
> lens at Surplus Shed ($22.50) - looks about right. 
> What do you think?  Is there a problem that it is
> fused silica rather than BK7?  (I am unlikely to
> work
> on mirrors larger than 12").
> 
> 
> - Gil
> 
> 
> FUSED SILICA PCX 75MM DIA, 250MM FL, 
> "Manufacturer's part #01 LQF 249. Original unit
> price:
> $220.00! 75mm diameter x 250mm focal length made of
> fused silica. Design index of 1.4601, design
> wavelength of 546.1nm. Clear aperture of 67.5mm,
> centration is 3 arc minutes. Center thickness is
> 9.3mm, edge thickness is 3mm. Edges are ground and
> beveled. An amazing price on a new precision fused
> silica lens!"
> 
> http://www.surplusshed.com/pages/item/pl1029.html
> 
> 
> 
> 
> 
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