Cold War Spoils: Amateur Builds Telescope With 70-Inch Lens

First time accepted submitter 192_kbps writes "Mike Clements, a long-haul trucker from West Jordan, Utah, built the largest amateur telescope ever with a whopping 70 inch primary mirror he purchased at auction. The entire telescope is 35 feet tall, 900 pounds, and he hopes to tour it in parks. As a hand-turned Dobsonian the telescope lacks the photographic capacity and tracking required for professional astronomy but the views must be breathtaking." (Are there other compelling candidates out there for "largest amateur telescope ever"? The 71" scope listed by nitesky.org appears to be dormant.)

Comments

Did he buy the mirror, or make it?

[DaTrueDave]

This is unclear to me:

"One of the riskiest parts of the project was turning the huge 70-inch piece of glass into a mirror by applying the silvering himself."

vs.

"Clements bought the 900-pound mirror — which was originally destined to go into space as part of a spy satellite until the edge of it was chipped during its manufacture — after it was auctioned off."

Re:Did he buy the mirror, or make it?

[Anonymous Coward]

He put a reflective metal coating on a purchased piece of glass with the proper final curvature.

Re:Did he buy the mirror, or make it?

[pla]

I took that to mean they just cancelled the satellite project after casting and polishing the mirror but before silvering it.

Alternatively, the intended use may have involved some classified exotic coating that serves some special purpose and they needed to strip the coating before selling the mirror at auction.

Re:Did he buy the mirror, or make it?

[Frobnicator]

I read it the same way.

They probably cut the mirror and polished the glass, and then the edge chipped.

A chip in the glass could be a fatal injury for a spy satellite as the article suggests was the intended use. Such telescopes use active optics to improve image quality; they apply pressure over the glass to bend it slightly. A chip could have micro-cracks and other damage that would easily spread across the surface. Without the actuators deforming the glass the image won't be as clear, but it would be good enough for a hobby telescope.

Once the glass chipped they likely just stopped the process, so the new owner would need to add the mirror surface on his own.

Re:Did he buy the mirror, or make it?

[Hadlock]

If you stick a 900 lb piece of glass on top of a rumbling shaking rocket and expose it to 5Gs of acceleration, rapid heating and cooling cycles etc, you probably don't want a chip in the glass where forces can propagate a crack. It's easier to make a new one rather than wait for it to fail in space.
 
For something that will only see occasional use with slow temperature changes it's ideal for a "low cost" telescope. It will still fail eventually, but it won't shatter in orbit while imaging a North Korean missile base (or whatever).

Re:Did he buy the mirror, or make it?

[necro81]

Reflecting telescopes use front-side mirrors. The glass is just there to provide the shape; it is not part of the optical path.

Re:Did he buy the mirror, or make it?

[Jeremy Erwin]

because a 70 inch reflector is interesting, but a 70 inch refractor is extraordinary. By not making the type of telescope clear in the headline, the submitter is practicing good click bait techniques. Not nearly as enticing as "Charlize Theron NSFW", but...

Re:Did he buy the mirror, or make it?

[mcmonkey]

"Charlize Theron NSFW"

I keep clicking on those words, but nothing happens :(

Re: Did he buy the mirror, or make it?

[send2erik]

No, you try to outpedant them by pretending that it doesn't matter.

Re:Did he buy the mirror, or make it?

[wagnerrp]

A chip in the glass could be a fatal injury for a spy satellite as the article suggests was the intended use. Such telescopes use active optics to improve image quality;

Why? It's in microgravity and temperature controlled. There's not going to be any sort of variation during operation to make active optics worthwhile. It's certainly not going to be adaptive optics, because you're moving across the atmosphere too rapidly to have any hope of keeping up with localized distortions. The only reason I could see it being useful is it would allow for more lax manufacturing tolerances, since you could fine tune it once you hit orbit.

Re:Did he buy the mirror, or make it?

[grep -v '.*' *]

"Charlize Theron NSFW"

I keep clicking on those words, but nothing happens :(

.... that you KNOW about :)

Re:Did he buy the mirror, or make it?

[umafuckit]

A chip in the glass could be a fatal injury for a spy satellite as the article suggests was the intended use. Such telescopes use active optics to improve image quality; they apply pressure over the glass to bend it slightly. A chip could have micro-cracks and other damage that would easily spread across the surface. Without the actuators deforming the glass the image won't be as clear, but it would be good enough for a hobby telescope.

Once the glass chipped they likely just stopped the process, so the new owner would need to add the mirror surface on his own.

Not so. Firstly, adaptive optics is still fairly rare and likely this mirror was never intended for use in such a telescope. Secondly, the mirror deformations on a telescope with adaptive optics are not done at the primary mirror (the large chipped one) but at the secondary or even tertiary mirror. It's much easier to do this on a small, thin, mirror than large, thick one. Finally, a little chip is no big deal. You just coat the mirror as normal then paint over the chipped area. You'll never see the difference. There are observatory mirrors out there into which someone unloaded a hand gun. They work just fine.

Re:Did he buy the mirror, or make it?

[HuguesT]

State of the art spy satellite require active optics because they look at things through the atmosphere. Not upward like a ground-based astronomy telescope, but downwards.

Re:Did he buy the mirror, or make it?

[Deadstick]

Why? It's in microgravity and temperature controlled.

When you're in orbit, "temperature controlled" is a slippery concept. You've got direct sunlight on one side, dark space on the other side, temperatures to the fourth power fighting it out, and no air to redistribute heat -- and an hour later, the sides will have switched.

Re: Did he buy the mirror, or make it?

[wagnerrp]

No. That's called adaptive optics, and it only works for ground based telescopes. There's no way in hell you're going to be able to adjust the mirror for atmospheric distortions when you're flying past it at 8km/s.

HST comparison, really?

[Arkh89]

According to TFA : enabling users to see constellations previously visible only through the $2.5 billion Hubble Space Telescope
Hahaha, but no...

Re:HST comparison, really?

[Virtucon]

Riiight.. I mean the guy lives in Utah so there are dark skies close enough to him but I'm plagued with air pollution and light pollution in my area and have to go at least 3 hours away to get a decent night of observation. Even then you still have upper atmospheric interference at times whereas the HST doesn't have any of that. The other problem I'd see with a Dobsonian of this size is maneuvering it and hauling it without damaging it. Props too him though for building it though, I wonder how many times he had to go to Home Depot to finish it?

Re:HST comparison, really?

[bruce_the_loon]

I think the problem here might be the word 'constellation'.

And that they're claiming it outperforms any of the other terrestrial telescopes from 70.1 inches up to the 409 inch Gran Telescopio Canarias, and presumably any bigger ones still being built.

Re:HST comparison, really?

[gandhi_2]

Actually, west jordan is in the massive sprawl complex that stretches from North Ogden to Nephi. He would probably have at least a couple hours drive to get up past Park City, Heber, Payson, or out towards the west desert, Tooele, or even Dugway He will have some driving if he wants darkness. Utah'ns in general take a "consumptive model" view of nature, and aren't big into reducing pollution, let alone LIGHT pollution.

Daily Mail is like National Inquirer

[Joining Yet Again]

Just a heads up for you non-Brits. There will be truth in this article... somewhere.

Re:Daily Mail is like National Inquirer

[HornWumpus]

FYI over the last 10 years or so the 'National Inquirer' has done more genuine 'investigative reporting' then the New York Times.

They have the nerve to report stories that 'the powers that be' have put an embargo on.

Re:Daily Mail is like National Inquirer

[GodfatherofSoul]

Let's not get hyperbolic. As many problems as I have with the NYT, a couple of sex scandals involving politicians doesn't measure up to what the NYT does every day. Now, take a look at what the Enquirer reports on every day.

Re:Daily Mail is like National Inquirer

[Jeng]

Yes, the National Inquirer may do more investigative reporting, but if no one believes it because 90% of what they report is false then who gives a fuck?

Re:Daily Mail is like National Inquirer

[GodfatherofSoul]

I won't matter what I reply with because you've already invoked the "real Scotsman" fallacy in your question. Anything posted won't count to you.

Largest Amateur telescope.

[Anonymous Coward]

Technically Lord Rosse (https://en.wikipedia.org/wiki/William_Parsons,_3rd_Earl_of_Rosse) was an amateur, and his telescope was 72 inches.

Re:Largest Amateur telescope.

[SuricouRaven]

It's not as impressive as it sounds. The title is heretitary, so it basically means 'My ancestors were filthy stinking rich, and I probably am too.'

When we want to grant someone a title of respect, they get the 'Sir' before their name, not Lord. You have to earn that one personally, not just get born into it.

Re:Largest Amateur telescope.

[careysub]

Lord Rosse's telescope used a cast speculum metal mirror, basically pewter, which had a reflectivity of 66%. Glass silvering technology had not been developed to a level adequate for astronomical mirrors. As a result the light gathering power of the 72" Leviathan of Parsontown was equivalent to a 58" mirror of 100% reflectivity. Clement's mirror is coated with silver, and with even a mediocre silvering job a reflectivity at least 90% should be obtained. This makes his mirror equivalent to a 66" mirror of 100% reflectivity, so it is a more "powerful" mirror.

Isn't there even one picture through it?

[Dr. Manhattan]

How hard is it to rig up a camera adapter? That'd help demonstrate exactly how powerful it is...

Re:Isn't there even one picture through it?

[BullInChina]

Even with tracking capability, which isn't that hard for a dobsonion, alta-azimuth mounts like this suffer from field rotation effects and exposures longer than about 30 seconds are not ideal. But you can take many 30 second exposures and stack them to give you something resembling a much longer exposure. The stacking de-rotates the images and aligns them.

Re:Isn't there even one picture through it?

[jeffb (2.718)]

Or you can build a rotating camera mount, or insert a rotating element in the optical path. Either way, you're supporting and moving a relatively small weight, so it's a much easier task than building the main drive.

Re:Isn't there even one picture through it?

[careysub]

Taking short exposures and processing them on a computer is the "poor man's adaptive optics". A very powerful technique (if the object is bright enough) is too take a large number (thousands) of short exposures, then sort through them for a "lucky" image - one in which the atmosphere is momentarily stable. Multiple lucky images can be stacked together to get longer exposures. This really is a very powerful technique, not requiring extremely expensive high precision tracking hardware.

Bad Headline: Mirror Not a Lens

[crunchygranola]

Here is the scoop on the 70" telescope. Mike Clements purchased a polished but uncoated mirror that is 70" across that was intended for a spy satellite project that was cancelled. A huge uncoated mirror is not a telescope anymore than (car analogy - wait for it...) a V8 engine is a racecar. Building a good performing telescope (collimation tolerances are measured in thousandths of an inch) is a significant task, a huge telescope like this is a major engineering feat. What's more this is a transportable telescope. It is possibly the biggest transportable telescope in the world. This telescope is more powerful than any telescope that existed before 1917 (when the 100" Hooker telescope saw first light).

Successfully silvering the mirror using updated 19th Cedntury mirror coating technology was nifty too.

Re:Trust me

[olsmeister]

No, but oriented in the proper way, you can start fires at random locations all over their property, causing them to believe that they have poltergeists.

Some further info...

[Zarquon]

Cloudy nights thread and a another news article.

It was silvered with a spray-on solution using a weed sprayer; much too large for the regular vacuum deposition chambers.

-R C

Re:Not a Lens

[BullInChina]

No not really the same thing at all. Both strategies will form an image but the physics are different. The mirror reflects the light via a paraboloid and thus forms the image without any chromatic abberation. For the lens to form an image the light must pass through the glass and because the speed of light in the glass depends on the wavelenght, the refractive index is slightly different for every wavelenght and the therefore the lens will show significant chromatic abberation. This is assuming that it is a single lens. Multiple element lens are possible to design with different refractive indicies that will minimize this effect but they are much more complex and expensive. Oh by the way the largest refractor ever built is the Yerkes telescope which is only 40" in diameter. Anything larger would distort under it's own weight.

Hats off to this man! And for once, the Eds..

[Bearhouse]

Truely "news for Nerds". Brings back fond memories of building 'scope and staring at the skies with my father.
This man has drive, dedication and the ability to both conceptualise and physically realise his dreams.

Instead of bullshit "surveys" with no-longer-funny "CoboyNeal" options, here's a serious suggestion - how about we instigate the /. annual "Nerd" awards?

Fuck it, this is going way offtopic, but I don't care...categories anyone?

Pics

[Flere Imsaho]

You don't really appreciate what an awesome amateur effort this is until you see pics http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/6146228/page/0/view/collapsed/sb/5/o/all/fpart/2/vc/1

Being the owner of an 8" Schmidt–Cassegrain scope, this blows my mind.

70- inch mirror, not "70 inch lens"!

[192_kbps]

Right after submitting this I noticed my goof in the title. As a refracting telescope the primary optical device is a mirror, not a lens. Slapping myself in the face.

Re:70- inch mirror, not "70 inch lens"!

[bruce_the_loon]

You might owe yourself another slap. It's a reflecting telescope. Grins.

My big lens story

[mknewman]

Years and years ago, around 1976, I had a tube type TV that went fritz so I took it to an Austin, Tx TV repair shop. The guy took it in the back to work on and while he was doing it I looked around his shop and there were quite a few very nice amateur astronomy photos, Jupiter, Saturn, the Moon and such. I was taking some astronomy classes at UT. When he came out we got talking and he told me he was into astronomy. Now, this shop was a WRECK, much like most TV repair shops I have ever seen. pretty much a dump. He asked me to come in the back to 'See something'. The guy was about 6'6" tall and BIG, and rough looking, and I am NOT, so I declined, but he insisted so I finally went through a maze of old junk, narrow dark halls, and finally got to the back of the store. I was kinda scared. He pointed to something on the ground. It was a round plug of glass on a large wooden palate. My jaw dropped, I asked him if it was what I thought and he confirmed it was a slug for a 6 ft telescope. I believe he said he got it at auction when a Swiss observatory had two made and the first worked out, so he got it cheap. It was unfinished, just a blob of glass, but at the time I'd only seen telescopes in the 36" range and this was huge! He was grinning ear to ear, and I was astounded. I believe his name was Chuck Knesek but I may be wrong or only close. It's been 35+ years. I never saw him again. If anyone knows what happened to him or his slug I'd love to know.

Re:Like HST (but not in a good way)

[the_other_chewey]

Remember how when it first went up, the hubble had problems focusing clearly? The designers forgot that its mirrors would be deformed/reshaped by the lack of gravity. Essentially, the hubble's primary mirror was optically designed to work as a telescope mirror on earth, not in space.

Uh, no. That would've been an amateur mistake to make and didn't happen.
Instead, the amateur mistake made was not to properly verify that the grinding
machine was actually grinding correctly. They even ignored measurments by
another instrument showing a faulty shape, assuming the instrument to be faulty instead.
And skipped the final post-assembly check to save time and money.

The mirror simply was ground extremely precisely into a wrong shape, and nobody noticed.

But as always in cases like this, the whole story is more complex and consists of a lot of
things not going as planned. It's a good and instructive read.