Differences

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--- arces [2026/01/30 01:27] – holtz
+++ arces [2026/01/30 04:34] (current) – external edit 127.0.0.1
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 ===== ARC Echelle Spectrograph (ARCES) =====
+The ARC echelle was constructed for the 3.5m at the University of Chicago in the 1990s.
+[[https://www.apo.nmsu.edu/mainpage/arces/arcesguide/|ARCES instrument manual on APO website]]
 ==== Features / issues ====
+* the traces and ThAr lines can move around over the course of a night. The reason has never been completely understood.
+  * This leads to issues with conventional 2D flat-fielding since it is possible that pixels with flux in an object spectra will not have pixels with a lot of flux in a flat-fielded image.
+  * This also affects the ability to get precision velocities. More frequent ThAr frames may be required, or you may wish to try to use telluric absorption to correct for wavelengths; see {{:wiki:arces:echelle_dispersion_note.pdf|note by Patrick Gaulme}} with his conclusions about the nature of the shift.
 * ARCES has a small aperture, giving a very short "slit". Sky is difficult, if not impossible, to detect/subtract
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 ==== Other resources ====
     * {{:wiki:arces:telluric.pdf|G. Catanzaro's spectra atlas of atmospheric telluric lines}} provides a great resource to identify the telluric lines in the ARCES data.
+    * {{:wiki:arces:pych_cr_removal.pdf | Paper on a possbility for removing cosmic rays from individual images}}
+==== Files ====
 {{medialist>wiki:arces:*}}