Your interest in the link between th Horus Myth and the "Christian Mythology" perhaps clouds your judgment. 

 I say this because most people who come to learn more about the link between Horus and Jesus, and who use terms like "Christian Mythology" tend to simply want to cement their view about how Christianity originated from Earlier pagan myths and to flesh the idea out. This tends to especially be true of those who claim an interest. 

 I realise this isn't assuming good faith, but its difficult to when you've faced this sort of thing before. 

 The truth is, there is no link between Horus and Jesus. Everything you have heard in Zeitgeist about it, and later in Religulous, is based on rubbish, that is completely unsupported by actual primary sources. 

 If you go to your local library and read any book on Egyptian mythology they have, you will not find mention of the specific similarities, like the virgin Birth of Horus, or his Crucifixion. Nothing about it is mentioned in any mythology book you care to look at. These parallels are only found in books that draw a direct link between Jesus and Horus. In other words, Christ Myther books. Thats the only place you will find the similarities discussed. 

 You won't find it in anything else, from the popular works of Victoria Ions to Oxfords Egyptological volumes. Each and every damning similarity used to show the link simply vanishes into thin air when you compare the claims to the Myth of Horus as presented by Scholarly works. IT becomes a Phantom you pursue into the shadows that grow long and dark, but lack real substance. 

 This Phantom can be pursued even to the original sources themselves, and translations of all can be found if you look, most online as they are now public domain. Here even there is only emptiness to greet the claims. 

  The Parallels between Jesus and Horus simply do not exist. If you want to study the origins of Christianity, then study it from the writings of the Church Fathers, the Bible (Yes I know how dreadful, using the Bible to study the History of Christianity), and modern Scholars who are recognized in the fields. Not all of whom are Christians themselves, and none affording a place at the table for consideration of the Christ Myth idea in general, much less the parallels suggested by you for inclusion regarding how Jesus and Horus are similar. 

 The truth is, there is no link between Jesus and Horus, and the Parallels in Zeitgeist and Religulous, and The Christ Conspiracy, and The Pagan Christs, and others, are nonexistent when you do real studies. In fact, they originate with 19th century Poet and Theosophist Gerald Massey, himself not an Egyptologist, and whose ideas are rejected and ignored by real Egyptologists. 

 If you want to study the Origins of Christianity, as I said earlier, study it from real sources. If you want to study the links between Christianity and Horus, there is nothing to study. 

  
 -SKills.