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The enhancement of carbon-14 in tree rings around AD 774/775 has generatedwide interest in solar activity at that time. The historical auroral recordshave been examined critically. Of particular interest was the "white vapour"observed in China on AD 776 January 12/13. Both Usoskin et al. (2013, Astron.Astrophys. 55, L3; U13) and Stephenson (2015, Adv. Sp. Res. 55, 1537; S15)interpreted this record as an auroral display. Subsequently, Neuh\"auser andNeuh\"auser (2015, Astron. Nachr. 336, 225; NN15) proposed five "criteria" forthe likeliness of aurorae and on this basis rejected an auroral interpretation.Instead, they interpreted it as a lunar halo, and suggested there were noauroral records as a proxy of solar activity in the interval AD 774-785. Weconsider if their "lunar halo hypothesis" and their auroral criteria could beof use in future researches on historical auroral candidates. We first show acounter-example for the lunar halo hypothesis from a parallel record on 1882November 17, which was seen as a whitish colour, in the southerly direction,and near the Moon. We then consider NN15's criteria on colour, direction, andsky brightness and investigate other counter-examples from early-modern auroralobservations. We also consider the extension of the white vapour in AD 776according to the distribution of Chinese asterisms, and show that its largeextension was inconsistent with the lunar halo hypothesis. Conversely, thestreaks of white vapour penetrating the eight Chinese asterisms can bereproduced if we consider auroral-ray structures at altitudes between 97 km and170 km, along geomagnetic field lines between the L-shells L=1.55 and 1.64. Ourinvestigations show that we should consider candidate auroral records inhistorical documents not on the basis of the newly suggested a priori criteriaby NN15 but on all the available observational evidence.

Do the Chinese Astronomical Records Dated AD 776 January 12/13 Describe an Auroral Display or a Lunar Halo? A Critical Re-examination