I'm not sure if it's customary to post code here or not, so for now I will leave it out, but if anyone wants to see how I did it I'll be happy to update.
Our first clue in this puzzle comes from:
The linked Wikipedia page, which gives a rather enticing way of converting from symbols to Latin characters in this picture: The characters in the OP are (pretty much) consistently written, so I made a Mathematica program to split the OP into its letters and then see what Latin character it corresponds to.
When we do that, we get a pretty big chunk of text:
chocfez okcor cpeoekhy chocfez
chocfez okcor ofcheor
chocfez okcor ofcheor okoldy
chocfez okcor cpeoekhy chocfez ykchdy
oekey okcor ofcheor cpeoekhy otcedo
okialy okcor ofcheor chocfez cpeoekhy
chocfez cpeoekhy ofcheor otcedo
chocfez ofcheor okcor otcedo
otydy okcor chocfez okialy otydy oekey
olor oekey okcor chocfez okialy otydy okcor
chocfez ofcheor otcedo
okialy okcor chocfez
cpeoekhy chocfez okcor ofcheor cpeoekhy otcedo
okialy chocfez cpeoekhy chocfez okcor oekey olor
chocfez oekey okcor ofcheor okialy
chocfez okcor ofcheor otcedo ofcheor ykchdy qoeeodcey
chocfez cpeoekhy octeey cpeoekhy otcedo
okcor ofcheor ykchdy cpeoekhy okcor
okcor ofcheor ykchdy ofcheor cpeoekhy ofcheor otcedo
okcor ofcheor ykchdy qoeeodcey otcedo ofcheor
chocfez okcor oekey okcor ofcheor ykchdy
otydy okcor chocfez cpeoekhy octeey
okcor ofcheor cpeoekhy otcedo
chocfez okcor ofcheor ykchdy
oekey okcor chocfez ofcheor cpeoekhy
dm ymzjv kj zoamioi dm zoami apq moyqzmoyqod oiq movqdxmvv
I'm sure you can see patterns in there already, but first and last lines of that especially look very different from the rest, so let's focus on those:
"Seon heofonsteorran" is Old English, meaning (roughly) "See the stars". The last line seems to be a different cipher from the rest of the text, which would make sense as it is also a separate image in the OP.
Based on the hint given in the comments:
The OP says "It fell out of page f68r1.", which is one of a few 'star guides' in the manuscript. It turns out that everything other than the first and last lines here is not encoded latin characters, but actual names of stars from the manuscript. Each line gives us a list of stars. For example, the last set of stars:
Corresponds to these stars in the diagram:
Which, when connected, give the letter N.
Proceeding similarly for the other sets of stars in the text (through a combination of Mathematica and tedious manual labor) gives us a 26-letter string:
This string contains every letter exactly once, suggesting a map to the alphabet, or substitution cipher:
And we can use that cipher to decode the very last message:
Our very last line:
"dm ymzjv kj zoamioi dm zoami apq moyqzmoyqod oiq movqdxmvv"
"se regol to gamenan se gamen mid eardgeardas and ealdspell"
Which is again Old English, meaning "The guide to playing a game of worlds and fairytales/stories". This immediately brings DnD to mind, but looking at the relevant xkcd's alt text, I think a different version is used here:
Druids and Dicotyledons
Or, using the manuscript's language:
Which is consistent with the cut-off text at the bottom.