[General] 【at】its biggest and brightest or its biggestand brightest?

[XW Rogers]

:-? I came across a sentence as follows:
On this day, the moon is said to be its biggest and brightest.

The book from which the sentence comes is intended for students, so I wanna make certain.

 

[Raymott]

The book from which the sentence comes is intended for students, so I want to make certain.

"On this day, the moon is said to be at its biggest and brightest."
It only makes sense with 'at' in it.

 

[Matthew Wai]

Will it make sense if "at its" is omitted?

 

[Raymott]

Will it make sense if "at its" is omitted?

Possibly. I'm having trouble with the "It's said to be". Surely astronomers know by now exactly when the moon is going to be at its biggest and brightest. I believe the sentence is more correct with "at it's" in it.
You could say, "On this day, the moon is said to be bigger and brighter than on any other day."