Arabic transliteration question

1
The Arabic word commonly Latinized as hyleg (etc) is vocalized by some (e.g., Neugebauer, Pingree) as hayl?j, and by others (e.g., Holden, Dykes) as h?l?j. Considering that the Persian word from which the Arabic is derived has hi- (as does the late borrowed Sanskrit form), the latter variant seems to me most likely to be right. Does anyone know whether the vocalization hayl?j is actually given in any text or dictionary?

2
In case this question is of even marginal interest to anyone else, I may note that Paul Kunitzsch (Mittelalterliche astronomisch-astrologische Glossare mit arabischen Fachausdr?cken, 1977) says that both vocalizations occur, but that h?l?j is preferable as being closer to the original Middle Persian word, and that the medieval transcriptions all reflect a pronunciation with ? rather than ay.