Re: [ATM] [atm_free] Re: The 16 inch Ultrathin ronchi pics

["Vladimir Galogaza" <vladimir.galogaza@zg.htnet.hr>]

Rick wrote:
>From the discussion on the interferometer group if the two beams from the
>cube exceed 5mm you induce astig. just by the limitations of the Bath.Now
your
>setup, from the photos I've seen the seperation of the cube from the
reflective
>mirror is more like 12-16mm.


David Rowe has expresion for Astigmatism of Bath, induced by COC
measurement.

OPD=D^2.d^2/16*Lambda*R^  ( Lambda waves)
I think that this is maximum OPD for this mirror (central ray and edge ray
OPD).

For David Davies mirror

D= mirror diameter  (403 mm)
d= beam separation (12-16 mm,  RR)
Lambda= 630 nm
R=2808 mm

OPD = 0.1  - 0.2 waves
I think this may be called Peak to Valey (PV). (Is that true David ?)

Dale reported Astigmatism  magnitude of 0.75   waves.

Regards
Vladimir.




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