incorrect third order aberrations in reflective system

[ajwitte]

Checklist

• I have searched the existing issues and discussions for a similar question or problem.
• I have read the documentation and tried to find an answer there.
• I am using the latest version of Optiland (if not, please update and retry).
• I have tried to reproduce or debug the issue myself before opening this.
• I have included all necessary context, such as version info, error messages, or minimal reproducible examples.

Bug Report

Describe the bug
In version 0.5.6, I am getting 0 for all seidels() except S5 for a cassegrain-like system. I don't think it is the same as issue #300 because I have multiple fields and because my invariant() is nonzero. This issue reproduces with the similar system optiland.samples.telescopes.HubbleTelescope.

To Reproduce

from optiland.samples.telescopes import HubbleTelescope
HubbleTelescope().aberrations.seidels()
# => array([0.       , 0.       , 0.       , 0.       , 0.0014539])

Expected behavior
The HubbleTelescope is a two-mirror system so more of the aberration coefficients ought to be nonzero.

Environment

• Optiland Version: 0.5.6
• Python Version: 3.10.11
• OS: Windows 11

[HarrisonKramer]

Hi @ajwitte,

Thanks for reporting this. I verified I get the same output for the Hubble example. I will look into this more closely, but I agree it is unexpected.

Do you happen to have the expected Seidels for this system, or, have you manually performed the paraxial calculations to determine them?

Regards,
Kramer

[ajwitte]

Thanks for the response!

As it happens... I came across this while working on some code to do third order analysis in SymPy. I don't have a lot of confidence in my own code yet although I have checked it against some textbook examples and was starting to cross check against Optiland. When I analyzed the Hubble example (except with a flat image surface) I got the following, which seems relatively sane:

[2.80642536737430e-6,
 -0.000337323248399191,
 0.00145177193503105,
 0.0128411858196848,
 0.00213750162702670]