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.

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.

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:

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:

f/5.5 Newtonian telescope with 5x telecentric tilted by 2° on optical axis:

Return to solar page

Return to home page