Hi! As already discussed in Episode 13 around the 1:22:00 mark, "red Borgil" is normally associated to Aldebaran, with other candidates being Betlegeuse and Mars. I think Betlegeuse can be easily discarded, and Mars is normally discarded due to two reasons:
1. Although it can be seen around midnight in late September below the Pleiades (Remmirath) and above Orion (Menelmacar), this is rarely the case.
2. The name for Mars is elsewhere (Morgoth's Ring) given as Carnil/Karnil.
I have read an interesting article (https://funkmon.wordpress.com/2014/01/06/identifying-borgil/) where it states that, since Carnil is Quenya for "red star", and Borgil is Sindarin for "red star", the association of Carnil with Mars would be an argument for identifying Borgil as Mars, not actually against it. I must agree here, as I think it would be unusual to give the exact same name in Quenya and Sindarin to two different stars.
As to the first counter-argument, I have been checking the night sky eastwards as seen from Oxford on every September 24th at midnight during Tolkien's life, and in 1943 Mars appears exactly where Borgil should be: between the Pleiades and Orion, at the same apparent height as Aldebaran. The nearest nights where this also happens (although not as perfectly aligned as in 1943) is 1928 and 1958. I attach an image of the sky on that night, but you can check it too at https://in-the-sky.org/skymap.php. Could it be possible that Tolkien took note of the position of the stars that same night, hence referring to Mars rather than Aldebaran? If one tried to describe the midnight eastward sky based on that night, I feel it would be difficult to give the "red star" title to an entity other than Mars. Or was that passage already fixed and not re-visited after that date, making this theory absoulte nonsense?

1. Although it can be seen around midnight in late September below the Pleiades (Remmirath) and above Orion (Menelmacar), this is rarely the case.
2. The name for Mars is elsewhere (Morgoth's Ring) given as Carnil/Karnil.
I have read an interesting article (https://funkmon.wordpress.com/2014/01/06/identifying-borgil/) where it states that, since Carnil is Quenya for "red star", and Borgil is Sindarin for "red star", the association of Carnil with Mars would be an argument for identifying Borgil as Mars, not actually against it. I must agree here, as I think it would be unusual to give the exact same name in Quenya and Sindarin to two different stars.
As to the first counter-argument, I have been checking the night sky eastwards as seen from Oxford on every September 24th at midnight during Tolkien's life, and in 1943 Mars appears exactly where Borgil should be: between the Pleiades and Orion, at the same apparent height as Aldebaran. The nearest nights where this also happens (although not as perfectly aligned as in 1943) is 1928 and 1958. I attach an image of the sky on that night, but you can check it too at https://in-the-sky.org/skymap.php. Could it be possible that Tolkien took note of the position of the stars that same night, hence referring to Mars rather than Aldebaran? If one tried to describe the midnight eastward sky based on that night, I feel it would be difficult to give the "red star" title to an entity other than Mars. Or was that passage already fixed and not re-visited after that date, making this theory absoulte nonsense?
