The humble Bridgeport and the Hubble telescope

[The_Yellow_Ardvark]

https://www.nasa.gov/content/hubbles-mirror-flaw

Ultimately the problem was traced to miscalibrated equipment during the mirror's manufacture. The result was a mirror with an aberration one-50th the thickness of a human hair, in the grinding of the mirror.

 

[fizzy]

https://www.nasa.gov/content/hubbles-mirror-flaw

Ultimately the problem was traced to miscalibrated equipment during the mirror's manufacture. The result was a mirror with an aberration one-50th the thickness of a human hair, in the grinding of the mirror.

That is a lot in optical terms.
Even amateur DIY scopes are far far better than that.

 

[daleyd]

That is a lot in optical terms.
Even amateur DIY scopes are far far better than that.

Better than 1 nanometer? Over a size like this?

 

[mtt.tr]

Everything in that picture is bloody amazing.

Yes it was made to the wrong measurments but bloody accurately wrong.

I don't know the the first think about lenses seems like which craft to me, i do know the precision is beyond just about all other manufacturing

 

[fizzy]

Better than 1 nanometer? Over a size like this?

YES!

They made it accurately enough - just not to the right spec.

The mirror is 240cm - a tiddler compared to some of the land based systems. 800cm is about the limit of a single mirror system - the bigger mirrors are segmented.

 

[pressbrake1]

Everything in that picture is bloody amazing.

Yes it was made to the wrong measurments but bloody accurately wrong.

I don't know the the first think about lenses seems like which craft to me, i do know the precision is beyond just about all other manufacturing

Lapping is a very accurate process
Jo blocks are one very common example

 

[mtt.tr]

Lapping is a very accurate process
Jo blocks are one very common example

I concede that but they are pretty small. Lapping a 10ft across lens is beyond my scope of imagination.

 

[daleyd]

YES!

They made it accurately enough - just not to the right spec.

The mirror is 240cm - a tiddler compared to some of the land based systems. 800cm is about the limit of a single mirror system - the bigger mirrors are segmented.

I know, I used to work for a company that made them - at one time we were actually part of the group that made the Hubble mirror (Pilkington - Perkin Elmer, PPE) but was just Pilkington Special Glass when I worked there in early 2000's

My point is that the mirror was never "out" by 1mm, it was "out of shape" by 1 micron. So, yes an embarrassing error that shouldn't have happened but not really comparable to making a small mirror.

 

[mtt.tr]

I know, I used to work for a company that made them - at one time we were actually part of the group that made the Hubble mirror (Pilkington - Perkin Elmer, PPE) but was just Pilkington Special Glass when I worked there in early 2000's

My point is that the mirror was never "out" by 1mm, it was "out of shape" by 1 micron. So, yes an embarrassing error that shouldn't have happened but not really comparable to making a small mirror.

Holding 1 micron over that distance is very impressive.

 

[daleyd]

Holding 1 micron over that distance is very impressive.

When I worked there we made some blanks for Lawrence Livermore University, something to do with fusion research IIRC - the tolerance on those was amazing, and that was before they went for polishing and whatever else after. The normal stuff we used to make for Canon etc was a walk in the park after that

 

[fizzy]

I know, I used to work for a company that made them - at one time we were actually part of the group that made the Hubble mirror (Pilkington - Perkin Elmer, PPE) but was just Pilkington Special Glass when I worked there in early 2000's

My point is that the mirror was never "out" by 1mm, it was "out of shape" by 1 micron. So, yes an embarrassing error that shouldn't have happened but not really comparable to making a small mirror.

No it was the measuring equipment that was out by 1mm.
But whatever the reason the mirror was giving useless images next to unusable.
They must have been so dissapointed after all that work and over 1 billion spend.
Shouldn't have happened.