2. The first star of Capricornus is according to my astronomy book Gredi (α), but we can see ξ is rising a few days earlier: 
At
the
other
end
of
Capricornus
is Deneb
Algiedi
(the
Tail
of
the
Goat,
δ),
which
is
marking
the
last
part
of
the
constellation
figure
(although
μ is
a
few
days
later).
Allen:
"Deneb Algedi is the transcription by Ulug Beg's translator of Al Dhanab al Jady, the Tail of the Goat; changed to Scheddi in some lists, - a name also found for γ." "These [α¹ and α²] are the Prima and Secunda Giedi, or plain Algedi, from the Arabian constellation title Al Jady." "In Persia it [Capricornus] was Bushgali, Bahi or Vahik, and Goi; in the Pahlavi tongue, Nahi; in Turkey Ughlak; in Syria, Gadjo; and in Arabia, Al Jady, usually written by us Giedi; all meaning the Goat, or, in the latter country, the Bādan, or Ibex, known to zoologists as Capra beden."
The name Deneb seems to be only a technical term for the end of a constellation; we can see it here evidently marks the tip of the right horn. The zodiacal sign of Aries is very similar to the head of the Ibex:
"Aratos called it Άιγοκέρως, the Horned Goat, to distinguish it from the Άιξ of Auriga, as did Ptolemy, but Ionic writers had Άιγοκέρευς; and this word, Latinized as Aegoceros, was in frequent use with all classical authors who wrote on astronomy. The Arabo-Latin Almagest of 1515 turned this into Alcaucurus, explained by habens hirci; and Bayer mentioned Alcantarus. Eratosthenes knew it as Πάν and Άιγι-Πãν, the Goat-Footed Pan, half fishified, Smyth said, by his plunge into the Nile in a panic at the approach of the monster Typhon; the same story being told of Bacchus, so that he, too, always was associated with its stars." (Allen) |
