Special Note Concerning Some Flux Spectra Obtained during Campaign 61

Special care should be used when comparing some spectra obtained on UTC 2014 May 26 and 27 with spectra from other epochs. Although the sky was essentially photometric on both of these nights, smoke from large forest fires in northern Arizona drifted over Kitt Peak. As a result, spectra of several blazars may be found to be redder than on other nights during Campaign 61. The effects of the smoke varies from object to object and is impossible to calibrate out of the flux data given the existing calibration observations. It is recommended that, if possible, spectra obtained during these two nights be checked against spectra taken on other nights during the campaign to determine if you wish to included these data in your analysis.

Polarization measurements and spectra are unaffected by the smoke. In addition, the differential photometry obtained during these nights is valid.