The saga of the Hubble telescope is quite a story
It started off with a major flub with the lens grinders.
Well not the grinders actually.
Those lappers did their job-precisely.
They were just given the wrong coordinates by some one in the blueprint department.
That caused a miscalculation in the grind/lap of this enormous glass disc.
Why ?
Because their null corrector was imprecise.
What’s null corrector?
Well its precise measuring device, a metal tube,
about the size of a beer keg,
with measuring lazar lights/
It kind of acts like straightedge.
Some one over looked a critical measurement by about an inch.
Anyway from this small imprecise beginning,
As we all know
when grinding glass,
the imperfection only gets magnified.
Well that not exactly right.
The lens was perfectly ground- imperfectly.
Out on the edge the lens was off by about 2.2 microns.
Not sure how minute 2.2 microns are?
According to the book it amounts to
A microscopic error in 70 million dollar grinding operation.
Didn’t get those first scratches out from the 180grit going to the 220 grit on your rock?
Well we all know how those minute scratches turn into deep ugly gouges magnified by our beautiful loving care serious oxide lamb skin polish.
Back to the 220!
Nose to the grindstone syndrome.
Back to the Hubble
This beautifully crafted 8 foot diameter lens was sent up to space as the Hubble telescope.
All went smooth as the Hubble was released from the space shuttle cargo bay
to orbit 400 miles high above earth.
Excited engineers, back on earth, eagerly awaited the first sent back pictures.
High anticipation!
And what do they get?
Blurry images! .
UUUUUUUUUUHHHHHHHHHHHGGGGGGGGGG!
We have problem Houston!!!
Mr Magooo
ground the lens.
But the fix these engineers accomplished (2 years later)
to correct this incorrect beautifully lapped lens is a marvel of ingenuity. Really!!
I won’t try to explain it because I already munched the above explanation above. Ha
But COSTAR was the fix.
I read about this in this book
Which is very informative and a precise description.
highly recommend reading by the mohs…
ground the lens. 
Uncle Albert...
all day
I distinctly remember forgetting that!