Match DESI arc lines selection to improve wavelength solutions

[ajmejia]

In PR #129 we tested the improved routines for wavelength/LSF fitting on our original selection of arc lines across different channels, with no significant improvements.

As an experiment in the NIR channel, we matched (as much as possible) DESI arc lines selection. This (combined with fitting a higher polynomial degree) lead to an improvement of ~0.03 (from 0.07 to 0.04) Angstroms in some cases. We can match DESI's selection in all remaining channels. This should significantly improve b channel wavelength residuals.

Related to this, the following are the remaining bugs in wavelength fittings in different cameras:

Clear outlying fibers in b3:

Systematic offset in some fibers (possibly block boundaries) in z3:

Clear break close to the middle of the chip (fiber ~331) while fitting a 5th order polynomial in z1:

The last one we explored a bit more. We tried replacing lines that show this bimodal behavior in the residuals with no success. This feature is present in all calibration epochs only in z1.

[ajmejia]

The bug in z3 is happening in sky fibers and could be a instrument feature being captured by the wavelength and LSF fitting.

The b3 one, seems to be related to a absorption-like feature that appears in fibers around 372 in arc line 3593 Ang.

[gblancm]

If the z3 problem happens only in sky fibers than it is most likely not associated with a detector artifact. I would suspect a problem with the initial guess being kind of far away after you jump over the gap from block to block.

…

On Fri, Aug 23, 2024 at 12:39 PM Alfredo Mejia-Narvaez < ***@***.***> wrote: The bug in z3 is happening in sky fibers and could be a instrument feature being captured by the wavelength and LSF fitting. The b3 one, seems to be related to a absorption-like feature that appears in fibers around 372 in arc line 3593 Ang. — Reply to this email directly, view it on GitHub <#131 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AIOKNY2237WP77JJJYVB6X3ZS5QUHAVCNFSM6AAAAABMEX4ZVSVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDGMBXGQZTMMBUGY> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

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[ndrory]

We consider this fixed in 1.1dev. Further improvements to wavelength solutions, if needed, should open a new issue.