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They Just Began Casting the Giant Magellan Telescope’s 5th Mirror. What a Monster Job.
Universe Today ^ | 11/7/17 | Evan Gough

Posted on 11/08/2017 8:10:47 PM PST by LibWhacker

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To: LibWhacker

This sucker won’t even start to come online until 2023.


21 posted on 11/08/2017 10:27:18 PM PST by lefty-lie-spy (Stay metal. For the Horde \m/("_")\m/ - via iPhone from Tokyo.)
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To: zeestephen

Any imaging success you get from CCD’s will only be improved by focusing incoming light using large mirrors. It makes sense to use both, which is what modern telescopes generally do.


22 posted on 11/08/2017 10:56:21 PM PST by Telepathic Intruder
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To: crz

We looked into making our own 8” mirror so the kids could see Halley’s Comet back in 1986. The basic grinding process was simple. As you got closer to the final surface shape, you had to wet the surface to make it reflective, then look at a sheet of graph paper placed several feet away.

Any mirror distortion was evident in the reflected image.

Once the reflected image was correct, you had to send the mirror off to have it coated.

We ended up buying an 8” silvered mirror and constricting the rest of the telescope.

http://www.scopemaking.net/mirror/mirror.htm


23 posted on 11/09/2017 1:09:02 AM PST by BwanaNdege ("The church ... is not the master or the servant of the state, but the conscience" - Luther)
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To: LibWhacker

Bump!


24 posted on 11/09/2017 1:23:57 AM PST by 4Liberty (MSM = Democrat' PR firm. Mainstream "news" = Fiat news.)
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To: zeestephen

As a physics Ph. D., I’m going to venture to say “No”, as to the general idea, because CCD’s don’t preserve phase information the way mirrors and lenses do.

“Let us now praise optics”


25 posted on 11/09/2017 3:05:59 AM PST by dr_lew (I)
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To: BwanaNdege

My best friend was part owner of a ship repair company with 4 other guys, one of them was into telescopes. They would grind their mirror, not sure of the size, at their meetings pushing and pulling back and forth. Took them awhile.

They used a sonotube?, one of those molds for pouring concrete pilings, as the body and built a Dobsonian? telescope that was very large. You had to stand on a stepladder to see into this thing.

I’ll never forget seeing the Orion Nebula through it. It looked just like the pictures in astronomy class I was taking at the time. I was amazed at the quality of the images, especally as it was a DIY project.


26 posted on 11/09/2017 3:38:20 AM PST by Comment Not Approved (When bureaucrats outlaw hunting, outlaws will hunt bureaucrats.)
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To: Telepathic Intruder

The CCD’s are chilled to reduce thermal noise. A computer is used to integrate the image - it gets to the point of counting individual photons hitting each pixel.


27 posted on 11/09/2017 6:52:02 AM PST by Fred Hayek (The Democratic Party is now the operational arm of the CPUSA)
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To: crz; Chode; Squantos; All
VERY, VERY CAREFULLY with Fine Polish Compound and LOTS of furry Bunny 🐰 wabbits. You hold them by the feet, dip their back into the Compound just a bit and Start Polishing.
28 posted on 11/09/2017 9:45:35 AM PST by mabarker1 (Progress- the opposite of congress)
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To: LibWhacker

Very Cool....
Thank You


29 posted on 11/09/2017 9:47:43 AM PST by mabarker1 (Progress- the opposite of congress)
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To: Comment Not Approved

Well, you’ve got me motivated now. I’ll have to consider building a telescope with the grandkids.

This time we’ll grind our own mirror! Last time we were in Kenya & the hassles shipping a DIY mirror out to be silvered mandated a ‘store-bought’ mirror.

Sonotubes are a great idea for the larger sizes, perhaps wrapped in a layer of fiberglass cloth & resin to make it water-proof. We used 8” aluminum irrigation pipe, IIRC.


30 posted on 11/09/2017 10:20:39 AM PST by BwanaNdege ("The church ... is not the master or the servant of the state, but the conscience" - Luther)
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To: dr_lew
Thanks, Doc.

I have always had great difficulty in understanding light, specifically, the particle-wave duality and the multitude of energy levels.

By “phase information” I presume you mean something like infrared, visible, ultraviolet, etc.

My original thought on this subject was, “Why not cover acres of ground with CCDs instead of spending 20 years casting and grinding mirrors?”

I had always assumed the issue was computer processing power for trillions and trillions of pixels.

31 posted on 11/09/2017 2:10:04 PM PST by zeestephen
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To: LibWhacker

960 inches or 24,384mm for the entire telescope.
24,384mm / 25mm = 975x magnification.
I guess we still won’t be seeing Martians.

Calculating Magnification
The magnification is the telescope focal length divided by the eyepiece focal length, in millimeters.

Magnification = Telescope focal length ÷ Eyepiece focal length

For example, if you use a telescope of 1000mm focal length with a 25mm eyepiece, the magnification would be 40x (1000mm ÷ 25 = 40). Doubling the power gives you one-fourth the image brightness and reduces the sharpness by one half.
https://www.telescope.com/Telescope-Power-Magnification/p/99813.uts


32 posted on 11/09/2017 2:47:32 PM PST by minnesota_bound
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To: Fred Hayek; zeestephen

But as always, the more photons the better when it comes to imaging dim objects farther out in space than anyone has yet seen. And for that you need more surface area, which means larger mirrors. CCD’s are the modern equivalent of photographic film; they just count photons, and need something to focus them first to form a meaningful picture.


33 posted on 11/09/2017 3:03:21 PM PST by Telepathic Intruder
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To: mabarker1
oh YEAH?

34 posted on 11/09/2017 3:32:26 PM PST by Chode (You have all of the resources you are going to have. Abandon your illusions and plan accordingly.)
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To: Telepathic Intruder
Re: “CCD’s are the modern equivalent of photographic film; they just count photons, and need something to focus them first to form a meaningful picture.”

Thanks - that's helpful.

Is it possible to mass produce an inexpensive lens for CCDs?

35 posted on 11/09/2017 9:34:32 PM PST by zeestephen
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To: zeestephen

If I knew how to make lenses cheaper, I would patent it before telling you. But I don’t think lenses themselves have changed in the last few hundred years.


36 posted on 11/09/2017 9:58:56 PM PST by Telepathic Intruder
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To: zeestephen
By “phase information” I presume you mean something like infrared, visible, ultraviolet, etc.

That's not it. "Phase information" charactises "coherence", as a laser, for example, is a coherent beam of light. This is what allows it to produce interference patterns.

You can shine a laser through a lens, and bounce it off mirrors, and this coherence will be preserved, but CCD's require absorption of photons, and so the information thus recorded is reduced to INTENSITY, as opposed to AMPLITUDE, which preserves or carries "phase information". So a surface of CCDs can never duplicate an optical mirror surface.

This is according to my own understanding, and I stand ready to be corrected, ( but it would take some doing! )

37 posted on 11/10/2017 9:12:17 PM PST by dr_lew (I)
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To: dr_lew
Thanks. That's helpful.

An earlier Comment said that a CCD was like the raw film in a camera - it just “counts” the photons.

It requires a lens to create a photograph.

So, tomorrow, I will be at You Tube watching educational videos about phase information, interference patterns, and amplitude.

38 posted on 11/10/2017 9:42:10 PM PST by zeestephen
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To: brytlea; cripplecreek; decimon; disndat; KoRn; Grammy; steelyourfaith; Mmogamer; dayglored; ...
Thanks LibWhacker. Ping to APoD members.

39 posted on 11/11/2017 1:00:35 PM PST by SunkenCiv (www.tapatalk.com/groups/godsgravesglyphs/, forum.darwincentral.org, www.gopbriefingroom.com)
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To: Comment Not Approved

“Dobsonian” -

That is a type of mount for a Newtonian. It was designed by John Dobson, well known amateur astronomer. I met him once at The Orange Blossom Special starparty in Florida. He was interesting, but, a bit of a mooch.

I’ve been using a scope for 45+ years now, and, have never seen any value in grinding my own mirror, when there are so many folks out there that make good ones relatively cheap. It takes all kinds though.

Now building a scope around a mirror is another thing all together. My current scope was hand made by a late member of our club. It’s a fine machine all together, but, the mirrors were bought, not, ground by hand.

All that said, the most important thing is once you get it ready, to go out and use it. Even in the suburbs there are things in the sky to see.


40 posted on 11/11/2017 5:10:11 PM PST by Conan the Librarian (The Best in Life is to crush my enemies, see them driven before me, and the Dewey Decimal System)
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