Sensitivity of a telecentric assembly to tilt
(Copyright Christian Viladrich)
Telecentric systems for solar observation
Tilted telecentric systems
Focuser "droop" case: What happens when a telecentric system is tilted ?
Suppose the telecentric assembly and the
etalon are aligned along the same optical axis, but with a tilt i
relative to the telescope optical axis.
In the following OSLO simulation (Newton 300 mm f/5.5 with 5x
telecentric) the telecentric system is tilted by 2° relative
to the telescope optical axis (solid line pink color).
Light comes from the left side.
![](Newton-300mm-tilt-2d.jpg)
The chief rays angle is no more normal to the etalon, but tilted by an angle on the order of i/M. This angle is relatively constant over the field covered by the camera.
Here are the results of the simulations of two configuration using ray-tracing software.
![](Tilted-telecentric-simulation.jpg)
The tilt of the chief ray results in a blueshift of the CWL and a
broadening of the FWHM of the etalon which can be calculated with the
formulae given on this page:
../FP.htm
Noteworthy, in both simulation the degradation of image quality
(spherical aberration, astigmatism, etc.) due to the telecentric tilt
is very limited.
f/5.5 Newtonian telescope with 5x telecentric, no tilt:
![](N300f5.5-tele5x-no-tilt-spot-diagram.jpg)
f/5.5 Newtonian telescope with 5x telecentric tilted by 2° on optical axis:
![](N300f5.5-tele5x-tilt2d-spot-diagram.jpg)
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