Here's the link to the ISOS project which allows access to the digital photographs of each page of the various manuscripts (MSS) in various collections in Irish libraries, universities and academies.
from this introductory page link click "next" and it will take you this page (or go directly to the below linke)
From here you can click into the online catalogues of the various institutions where ancient MSS are kept. From here you will be able to view MSS of your choice - such as The Book of Ballymote (contains the ogham tract), Lebor na hUidre - Book of the Dun Cow (contains the Táin Bó Cuailgne saga), The annals of the four masters, the Book of Armagh (Contains St Patrick's breastplate), etc etc.
The digital photos are of high quality and give you a good appreciation of the beauty and skill of the scribes who created such manuscripts.