Hi,
I am trying to know the orion St120 flat field circle size without flattener. anyone know what is the size of it? anyone have image sample without flattener?
thanks
Kimo
anyone know ST120 flat field
- orly_andico
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Re: anyone know ST120 flat field
Refractors have a field curvature equal to their focal length. The ST120 is f5 I suppose so 600mm focal length.
It will need a flattener for any decent size chip. For a small chip like an ICX285 I think you can get away without one.
Rule of thumb, any refractor below 1000mm will need a flattener for 4/3 or DSLR chips. Unless it's a flat field refractor like a televue or Takahashi.
It will need a flattener for any decent size chip. For a small chip like an ICX285 I think you can get away without one.
Rule of thumb, any refractor below 1000mm will need a flattener for 4/3 or DSLR chips. Unless it's a flat field refractor like a televue or Takahashi.