The analyses of a text #1

The narrator recalls his childhood; now he is at the boarding school near London, and today is his birthday.

How well I recollect the kind of day it was! I smell the fog that hung about the place; I see the hoar frost, ghostly, through it; I feel my rimy hair fall clammy on my cheek; I look along the dim perspective of the schoolroom, with a sputtered candle here and there to light up the foggy morning, and the breath of the boys wreathing and smoking in the raw cold as they blow upon their fingers, and tap their feet upon the floor.
[David Copperfield by Charles Dickens]
I think "ghostly" modifies "frost."
So I was wondering why it is "the hoar frost, ghostly," not "the hoar ghostly frost."
And I'd like to know if "to light up" modifies "candle," means "in order to light up."
Thank you in advance for your help.