would adding a iris help?

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would adding a iris help?

Post by highfnum » Wed Sep 30, 2015 8:28 pm

would adding an a variable iris between slit and collimator lens help with
either focusing or contrast

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Re: would adding a iris help?

Post by Merlin66 » Wed Sep 30, 2015 11:17 pm

I think the best you could hope for would be a possible reduction in scattered light.
The long slit used on the SHG means that the effective light cone between the rear of the slit and the collimator is larger than on a normal astronomical spectrograph. Joe uses a field lens just behind the slit to improve the possible vignetting on his large Littrow design.
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