BBC Sky at Night Magazine presents How to Grind a Mirror

BBC Sky at Night Magazine presents "How to Grind a Mirror". This is an instructional video by Terry Pearce and Simon Lang. You can see the full length (40 mins) version at www.bbcskyatnightmag.com/mirror_video.asp To subscribe to the popular magazine click here https://www.subscribeonline.co.uk/bbc-magazines/subscription.cfm?mag=SKAN&...

Category:

Science & Technology

Tags:

• Sky
• at
• Night
• Mirror
• Telescope
• grind
• BBC
• magazine
• Terry
• Pearce
• Simon
• Lang

[Skygeezersi]

Thx for your comments, this short's a taster for the longer 40 minute version. You can make grinding machines to lessen the load however unless you want to make lots of mirrors or big ones it's impractical. Grinding to achieve a spherical curve is surprisingly easy...the polishing and parabolic 'figuring' is where you have to be more careful but it can all be done by hand. Seeing stars and planets your own mirror is profound...you in touch with your universe. 200mm mirror achievable in 5 days.

[david85allen]

The full video is here. I found it after about an hour looking - just search for p0iyRgRhvLk in youtube.

[gettingahandle]

all this so his wife can see her face more clearly. what vanity

[MrUnclestupidhead]

And I thought it took months!

[rapsod1911]

Where I can find full video?

[bethpage89]

@DanFrederiksen:

The tile grinding tool is made conave so it is the mate of the roughly concave mirror. They mutually grind each other, and mutually spheroidal shapes naturally result.

Parabolization is done by polishing against the pitch lap.

With a 1 meter mirror the parabolization is begun during the grinding, because in that case the thickness of the glass to be removed is too much to be done by just polishing on the pitch lap.

[ParaglidingManiac]

How much does a mirror blank cost?

[DanFrederiksen]

don't those grinding tools require enormous precision when done like that??

I don't understand why people don't make some kind of grinder on a pivot such that the shape shows up naturally and could even be powered so as to not require enduring manual labor. that way it should also be straight forward to make 1meter mirror or even larger

[2plus2is9]

looks like a lot of work!

[demjp8RqDA]

BBC just mixes like that, who knows why. I have a number of BBC productions on DVD where I can barely hear the narrator over the music.