This reminds me very much of grinding limestone slabs in the printmaking studio: http://instagram.com/p/fGcGwdwAT1/
(Printmaking studios make good hackerspaces, and lithography has fun Chemistry involved. Etching has a little too.)
How do you turn a chunk of glass into a telescope mirror?
11–20 of 36 posts
Re: How do you turn a chunk of glass into a telescope mirror?
#12Yes but can you make a mirror like Kent did in Real Genius? "KENT: See! Do you have any idea how hard it is to make a film virtually 100 per cent reflective, one micron thick and apply it to a mirror this shape?" http://fringe.davesource.com/Fringe/Entertainment/Scripts/Re...
That may be the line in that script but it wasn't in the actual film. He just says something about making the "phase conjugate tracking system mirror" or something to that effect. That must have been some sort of "working script" as I recognize many other lines that were different or omitted in the final film.
Re: How do you turn a chunk of glass into a telescope mirror?
#13Earlier quoted context omitted.
Why did you eat the grinding powder?
It is sticky, very hard to wash and gets everywhere.
It is also dangerous to inhale these powders. They are very fine and very abrasive.
One needs to maintain a clean-room environment, both for the protection of the mirror from dust, and of yourself from the abrasives.
Re: How do you turn a chunk of glass into a telescope mirror?
#14I have grinded two 8" mirrors. The first one took three years (calendar time) and was a disaster. Lots of scratches on the mirror and astigmatism. I didn't give up though. Built a second one, applying all tricks that I learnt during the first experience. It turned out very good and only took an year to make. The linked page doesn't talk about the most painstaking part: the figuring and polishing of the mirror. A good…
OT: You are the second poster in this discussion to use 'grinded', instead of 'ground', as the participle of grind. I'm just curious whether that's telescope lingo or just your word choice?
I don't want to call it an error, exactly, because it seems to be part of a trend of verbs being regularised in American English. Lit => lighted etc. I read a novel the other day (Brandon Sanderson's new effort) that repeatedly used 'shined' instead of 'shone' and it was oddly distracting. I wonder how long it will be until all verbs are regular?
Re: How do you turn a chunk of glass into a telescope mirror?
#15A few more resources here: http://www.telescopelab.com/index.php?page=testing How to make blanks: http://www.mdpub.com/scopeworks/blanks/index.html
Probably more for inspiration than for tips: Opticks by Isaac Newton. He does go into detail as to how he ground his lenses, but that advice may be a bit outdated.
Re: How do you turn a chunk of glass into a telescope mirror?
#16I have grinded two 8" mirrors. The first one took three years (calendar time) and was a disaster. Lots of scratches on the mirror and astigmatism. I didn't give up though. Built a second one, applying all tricks that I learnt during the first experience. It turned out very good and only took an year to make. The linked page doesn't talk about the most painstaking part: the figuring and polishing of the mirror. A good…
OT: You are the second poster in this discussion to use 'grinded', instead of 'ground', as the participle of grind. I'm just curious whether that's telescope lingo or just your word choice? I don't want to call it an error, exactly, because it seems to be part of a trend of verbs being regularised in American English. Lit => lighted etc. I read a novel the other day (Brandon Sanderson's new effort) that repeatedly us…
http://grammarist.com/usage/grinded/:
"Grinded might be considered incorrect in some contexts, but it has grown more common over the past several decades. It’s especially common in American sports commentary and writing, where grind means to overcome adversity by playing hard."
And no, I don't think all verbs will become regular. Ew verbs tend to be, and it is easier for non-native speakers to have regular verbs, but verbs like 'to be' or 'to have' will keep aiming for conciseness (even though we have "me be hungry" as a sort-of counterexample)
Re: How do you turn a chunk of glass into a telescope mirror?
#17I have grinded two 8" mirrors. The first one took three years (calendar time) and was a disaster. Lots of scratches on the mirror and astigmatism. I didn't give up though. Built a second one, applying all tricks that I learnt during the first experience. It turned out very good and only took an year to make. The linked page doesn't talk about the most painstaking part: the figuring and polishing of the mirror. A good…
OT: You are the second poster in this discussion to use 'grinded', instead of 'ground', as the participle of grind. I'm just curious whether that's telescope lingo or just your word choice? I don't want to call it an error, exactly, because it seems to be part of a trend of verbs being regularised in American English. Lit => lighted etc. I read a novel the other day (Brandon Sanderson's new effort) that repeatedly us…
[deleted]
Re: How do you turn a chunk of glass into a telescope mirror?
#18I have grinded two 8" mirrors. The first one took three years (calendar time) and was a disaster. Lots of scratches on the mirror and astigmatism. I didn't give up though. Built a second one, applying all tricks that I learnt during the first experience. It turned out very good and only took an year to make. The linked page doesn't talk about the most painstaking part: the figuring and polishing of the mirror. A good…
OT: You are the second poster in this discussion to use 'grinded', instead of 'ground', as the participle of grind. I'm just curious whether that's telescope lingo or just your word choice? I don't want to call it an error, exactly, because it seems to be part of a trend of verbs being regularised in American English. Lit => lighted etc. I read a novel the other day (Brandon Sanderson's new effort) that repeatedly us…
I didn't consciously use 'grinded'; my mind just blurted it out based on what I may have read before. Thanks for pointing it out; though I do wish for a more regular English grammar.
Edit: I also just realized I typed "an year". This one was just sloppy.
Re: How do you turn a chunk of glass into a telescope mirror?
#19A few more resources here: http://www.telescopelab.com/index.php?page=testing How to make blanks: http://www.mdpub.com/scopeworks/blanks/index.html
Probably more for inspiration than for tips: Opticks by Isaac Newton. He does go into detail as to how he ground his lenses, but that advice may be a bit outdated.
Best classical reference (yet somewhat more modern than Newton) is:
How to make a telescope by Jean Texereau
Re: How do you turn a chunk of glass into a telescope mirror?
#20A few more resources here: http://www.telescopelab.com/index.php?page=testing How to make blanks: http://www.mdpub.com/scopeworks/blanks/index.html
Probably more for inspiration than for tips: Opticks by Isaac Newton. He does go into detail as to how he ground his lenses, but that advice may be a bit outdated.
Gordon Waite's cheap DIY spherometer tutorial: https://www.youtube.com/watch?v=htBx5SRFeMI&feature=related