Sunday, February 21, 2010


Down with Love

Sure am. The older I get, the more I think it's the one thing us sentient primates have going for us as we revolve endlessly around our puny G2V star. Love. It really does make the world go ‘round. Love is great, even, yes, the love of a young amateur astronomer for shiny new telescopes. Like the amazing Celestron Pacific Blue and White tube Schmidt Cassegrain telescopes.

“Blue ‘n Whites? What the hail are you a-talking about Unk? Celestrons, everybody knows, have mostly come with orange, black, and gray tubes. Oh…white…yeah, the brand-spankin’ new Celestron Edge HDs. They have white tubes, don’t they? Is that it?” Nope. Well, yeah, the new Celestrons have white tubes, but it ain’t them I’m talking about. What I am talking about is Celestron’s first line of SCTs, the C6, C8, C10, C12, C16, and the vaunted and legendary C22 that ruled the roost during the company’s first heyday in the 1960s.

These were the first Celestrons to make li’l Rod’s heart go pitty-pat, the Blue ‘n Whites, so called because their gleaming white tubes were set-off by luscious royal blue mirror cells and mounts. Actually, I didn’t know they were BLUE and white for quite a while. All I had to go on was the black and white pix in Sky ‘n ‘Scope. I certainly couldn’t afford one of my own to examine, seeing as how the C10, the most popular Blue and White, went for about two stinking grand in those days of yore.

What’s got me to reminiscing about the early times of everybody’s favorite CAT company? This is the Big C’s 50th year, and one of the things they have done in acknowledgement of that milestone is run a full page ad in the January 2010 Sky and Telescope featuring pictures from their storied past. I have had a lot of questions about one of those pictures: “What IS that great big SCT in the ad, Unk Rod? What is it, huh, what is it?”

So I figger it’s time to edumcate you sprouts about the history of one of the big players in the amateur astronomy game. I certainly won’t be able to do much more than summarize here, though; if you’re fascinated by Blue ‘n Whites or the Orange Brigade that followed them, I heartily recommend Bob Piekiel’s ebook Celestron: The Early Years (available through Astromart). Bob is DA MAN when it comes to Celestron history. I can at least hit the high points, this week and next, however.

OK, but what’s with the “Down with Love” stuff? If you’re as old as Unk, it’s possible your Mama made you squirm through some of the Doris Day/Rock Hudson sex comedies at the moving picture show just like Rod’s Mama did. Well, a few years back Director Peyton Reed made a spoof-cum-loving homage to those corny films of a simpler time with Down with Love, which starred Renee Zellwegger and Ewan McGregor. Not much of a movie, I ‘spose, but cute enough. Unk and Miss D went to see it mostly for nostalgia’s sake, and it turned out the filmakers had at least done that real well. A scene near the end prominently features a beautiful Blue and White Celestron C10.

Yes, Celestron has, hard as it is for me and my contemporaries to believe, accumulated half a century of history. That history began modestly with a young southern California electrical engineer, Tom Johnson. Tom, who owned a small company, Valor Electronics, which was producing power supplies and similar items for the burgeoning California high-tech/aerospace industry, decided he’d like to have a telescope so he and his kids could have a look at the night sky.

Mr. Johnson must’ve been pretty tickled with telescopes and astronomy, since he didn’t stick with the little 4-inch he bought for him and his younguns. Before long he was building his own telescopes, and, in an amazingly short period of time, he was showing off a home-brew 18-inch Cassegrain at star parties (yes, there were star parties, a few, even way back when). An 18-inch telescope was a huge—to put it mildly—amateur instrument for the time, and Tom’s big dog garnered a lot of attention, including an article in the March 1963 Sky and Telescope.

All the publicity and interest his ATM masterpiece generated got Tom to thinking. Might there be a market for semi-mass-produced large telescopes? Something for small colleges and the like, who wanted capable telescopes, but who couldn’t dream of calling somebody like Boller and Chivens and forking over a hundred grand. Certainly, he thought he could do better than the shaky, old fashioned Newtonians some of the amateur-oriented telescope makers were offering to schools. Maybe even better and more convenient than his cool Cassegrain.

Why not something like a Schmidt Cassegrain? A lotta folks think Tom Johnson invented the SCT. He didn’t. The melding of the telescopes of Schmidt and Cassegrain had happened some time earlier—advanced ATMs had been showing lovingly crafted chef d’oeuvre SCTs at places like Riverside and Stellafane for a while. After all, making Schmidt’s camera into a visual scope is a pretty doggone obvious thing to do. Do that and you get a highly portable telescope with a nice low-coma (relatively speaking) field. No, Tom didn’t invent the SCT—what he did was make it practical.

I shouldn’t have to tell you CAT fanatics—you vet’rans, anyhow—that the problem when it comes to making an SCT is that consarned corrector plate. Lotsa wet-behind-the ears novices assume it’s just a piece of flat glass that holds up the secondary. Not hardly. SCTs use fast (f/2, or thereabouts) easy to machine-make spherical primary mirrors. You can use a spherical mirror to look at the sky, but unless its focal ratio is up around f/10 plus, images are a mess. You get spherical aberration, the problem that devilled the pore Hubble Space Telescope when it was first launched. It’s somewhat like chromatic aberration in that all the rays of light delivered by the mirror don’t come to focus in the same plane, resulting in punk images.

Bernhard Schmidt’s revolutionary idea, which came to him not long after World I, was the corrector plate. It’s a thin, flat-appearing lens. It is a lens, though, which is high in the middle, lower out toward the edge, and high again at the edge. It’s what the bright boys call a “complex 4th order curve.” For ignorami such as Unk it’s enough to say that the corrector undoes the mirror’s spherical aberration. Or, if’n you wanna get slightly more technical about it, what it does is introduce a negative amount of spherical aberration, enough to cancel out the positive spherical aberration inherent in the primary. It works amazingly well, but, as hinted above, it has a problem: a corrector is hard as heck to make.

One way you can make a corrector is by hand-grinding, polishing, and figuring one. That is hideously difficult, so difficult that even that one-armed optics wizard, Bernhard Schmidt, figgered he’d need to come up with a trick. He did. His method, which is still used, is to place a corrector blank in a special fixture, a “vacuum pan.” The blank forms one wall of a vacuum chamber. After a vacuum is “pulled,” the exposed side of the blank is polished flat. When the vacuum is finally released, the blank almost magically assumes the correct shape for a corrector. It sounds easy, but in practice it's most assuredly not. You have to apply the correct vacuum and maintain it exactly, which is not easy to do. That is only the start of the complications. Doable, but more suited for custom one-offs than for the mass production Tom Johnson envisaged.

While waiting on the delivery of an expensive custom-made corrector plate he had ordered from a big optical house, Mr. Johnson put on his thinking cap and started messing around in Valor Electronics’ primeval optical shop. By the time the corrector arrived, he didn’t need it any more. He’d cracked the “code” for mass producing corrector plates.

Johnson’s method was not completely different from Schmidt's. He still pulled a vacuum against a blank. The “outer” side was polished flat, and when the vacuum was released he had a corrector. But there was one very important difference. Instead of using a vacuum pan, Johnson pulled the blank against a premade glass “mold,” a thing he called a “master block.” A master block was and is (Celestron uses the Johnson method to this day) a precision-made corrector form figured into the opposite of the shape desired for the finished lens. It’s easier, far easier, to get correctors right quickly using a master block than a vacuum pan.

Corrector-making still ain’t easy, even with the aid of a master block. Firstly, a master block has to be made and made exactly right. Then you run into problems like maintaining perfectly even contact between block and blank. Everything has to be kept nearly clean-room clean. Specks of dust trapped between the master block and corrector blank will result in contrast-reducing bumps in the finished corrector plate. For these reasons, amateurs or anybody else making one-off correctors still use the vacuum pan method. But in a factory setting, Tom Johnson’s master blocks worked well and simply, allowing him to spit out corrector plates with near abandon. That solved, the rest of the telescope was fairly easy to do, even if it took Celestron some cutting and trying to arrive at the design which has spelled “SCT” for the last 50 years.

The first “Celestron,” to take on form and substance, the Celestronic 20, don’t look much like the telescopes we’ve come to know and love. It was a big, hulking mutha with a long tube. It was an SCT, true, but it was prominently mentioned in its few ads that it could also be easily converted to Newtonian or to Schmidt Camera operation.

From what I can determine, the Celestronic never made it past the prototype stage. Oh, Valor ran some smallish ads, but apparently nobody dared order a big mama from this unknown little firm--not yet--so no production Celestronic 20s were ever built, and it was eventually disassembled and sold as parts. The Celestronic, which was really just a prototype anyway, was shortly replaced by the much more SCT-looking C22 (T.J. had found a stash of 22-inch rather than 20-inch blanks and decided to use ‘em). Oh, and the name on the ads that continued to appear in Sky and Telecope evolved from “Valor Electronics,” to “Celestron Pacific, a Division of Valor Electronics” to just “Celestron Pacific.”

And suddenly these white-tube/blue trim scopes began to sell. Largely because the C22, which cost an astonishing 35 grand (equivalent to 250,000 or MORE 2010 dollars depending on how you calculate such things), was soon joined by more affordable little sisters: a C16, a C12, a C10, a C8, a C6 and even a C4). None of them was exactly cheap, with the most popular of these Blue and White beauties, the C10, costing about the same as a new Volkswagen Beetle. Nevertheless, in addition to schools, a few amateurs, mostly those approaching the Johnny Carson class, could afford ‘em and bought ‘em. If nothing else, the Blue ‘n Whites caught the eyes of rank and file amateurs, ensuring we’d be ready for Celestron when Celestron was ready for us.

What were the Blue and White scopes like? You may be able to find out for yourself. A substantial number of C10s were made. They are not exactly a common item, but they do turn up at star parties once in a while, and it’s even possible to find ‘em for sale at prices that are pretty reasonable considering how much they cost when new. They are, ya see, not exactly antiques, nor are they exactly collectors’ items. Their owners tend to use them, and used C10s are priced as working telescopes rather than as heirlooms. A C10 in decent operating condition may sell for not much more than $1500 - 2000.

What will today’s amateur get for that money in terms of performance? Naturally, you can forget fancy electronics and high tech coatings, but these telescopes stand up well. The optics are almost always first-rate, and the scopes include features not seen in the Orange Tubes—or even the most modern Celestrons. One big plus is their lack of focus shift. Modern SCTs focus by moving the primary mirror back and forth via a single threaded rod. That works, but tends to push or pull the mirror slightly out of level with regard to the baffle tube it slides on. Despite the fairly tight tolerances of today’s Celestrons, that makes the images move back and forth in the field as you turn the focus control. The Blue and Whites also used moving mirror focusing, but rather than one threaded rod to move the primary, they used a set of three belt-connected spindles, eliminating focus shift.

That’s not the end of their niceties, either. In addition to collimation by adjusting the secondary mirror as in modern CATs, the Blue and Whites had primary mirror adjustments as well. And, while, no, they didn’t have much in the way of electronics, some of the scopes’ drive systems were decidedly more advanced than the “plug in, she runs, unplug she stops” of the Orange Tubes that followed them.

Optically, the Blue and Whites, are quite impressive. Find yerself a good condition C16, and by the time the night is over, you may forget you are using your granpappy’s telescope. Only slight downcheck here is that the focal ratios of most Blue and Whites come in at f/12 rather than f/10. That’s not a huge field-penalty, though, and may contribute somewhat to their unusually good performance. Some of the smallest scopes, by the way, could be ordered in differing ratios; the C6 could be had either in the “astronomy/telephoto” speed of f/10 or in the “guide scope” focal ratio of f/20.

So why in the heck have most of us never seen one of these wonderful telescopes in person? They didn’t last long. Celestron began to phase ‘em out in 1970, and by the end of that decade they was Gone Pecans. The reason being that the company had decided to change gears. It became obvious the SCT design potentially had wide appeal, and that if Celestron could offer telescopes that were at least realizable dreams for the average amateur astronomer, they could clean up. So were born the vaunted Orange Tubes, starting with the familiar C8 in 1970.

Before Celestron could sell SCTs to Mom and Pop Amateur for “reasonable” prices, they had to figure out how in tarnation to do that. The answer, not unexpectedly, was “simplify, simplify, simplify.” Starting with the lovely three-spindle focuser. That was gone, replaced with the single spindle model we still know and cuss. In truth, if everything is done properly, the system works pretty well, it must be admitted, and is capable of keeping that annoying movement during focusing to under 1-arc minute.

What else? How about the adjustable primary mirror? Johnson and company (which now included Alan Hale) had decided not only would having both an adjustable secondary and primary be confusing for the average amateur, it was really not needed. As long as the optical system, primary, secondary, and corrector, was properly assembled, the scopes could be perfectly collimated with just the secondary. Easier for owners—and cheaper for Celestron.

A few other things went at this time as well. The drive for the C8 was, as above, plug-to-go-unplug-to-stop, the mounts were leaned-up a bit, and some frills that were deemed unnecessary given the engineering advances Celestron had made over the previous decade were discarded—the spring-assisted mirror fixture in the primary cell, which was intended to improve focusing/mirror stability, for example.

With the sound of an air boat roarin’ from the swamp, out came the Celestron C8 “Orange Tube.” I doubt I have to tell you why this scope has become known and loved as the Orange Tube (Celestron never referred to it that way officially back then); a look at its picture tells the tale. What is not sure is why Johnson decided to paint his new telescope orange. To stand out from the crowd of 1960s white-tube telescopes? Because he got a good deal on orange paint? Who knows? Whatev’, it was a beautiful thing, with its sand-cast drivebase and fork, and hit amateur astronomy like a ton of bricks.

Not that all of us—or many of us—could afford one, mind you. Once you paid for everything, you’d be forking over close to 1000 1970 buckeroos, which is equivalent to about 5,000 of our microscopic dineros. Unk, for example, paid less than two thousand for a very good condition Ford Mustang at about that time, and found it rather difficult to come up with that sum. Still, the cost of the Orange Tube was something most of us could at least imagine accumulatin’. The pluses the C8 brought to the table seemed well worth it as the 70s rolled on. I mean, can you imagine packing a 1960s-style 8-inch f/8 Newtonian into the back seat of a Chevy Vega? I thought not. We couldn’t either. Despite the slightly scary price-tag, the C8 began to sell like the proverbial hotcakes, and the company’s competitors began to drop like flies.

So well did the C8 do that Celestron was soon adding to the OT stable. First there was the C5, followed shortly by the C14 at t’other end of the aperture scale. A few years down the line, Celestron filled-in with the much-loved C11. All these telescopes were much like the C8, with only the C14 adding more features. Even the 14-incher, with its more complex drive system and a few other frills (like a tube that was designed to be removed from the forks for easier transport), is much more like an Orange Tube C8 than a C16.

Celestron discoed through the 1970s seeming to go from strength to strength. The competition? They fell like dominoes. Criterion tried its own SCT in a bid to compete, failed badly with the Dynamax, and was soon on its way to the knackers at Bausch and Lomb. Other renowned names like Unitron, Cave, and Starliner either fell by the wayside or reduced their output so much that they might as well have. The amateur’s best friend, Edmund Scientific, held on to its astronomy business, but maybe just by the skin of its teeth. As the 1970s closed, Celestron was on the top of the world, Ma.

Tom Johnson must be a believer in Unk’s fave saying, “The Only Enemy of Good Enough is More Better,” because the company adhered to that for a cotton-pickin’ decade. Oh, they added new products—Schmidt cameras and a cute li’l 90-mm MCT amongst other things—but the bread and butter, the SCTs, remained mostly unchanged until disco well and truly began to suck. Other than minor changes in paintjobs and castings, an Orange Tube was an Orange Tube for ten years.

Then, in 1980, the changes began to come thick and fast. Startin’ with Tom Johnson’s decision to sell the little old telescope company from Torrance. Tom had given his all for over twenty years, and who can deny he deserved a retirement? Certainly, if I’d a-wanted to sell a telescope company, this is the time I’d have chosen, with the notorious comet Halley loomin’ on the horizon. The buyer? A Swiss manufacturing/holding company called “Diethelm.” At first, this seemed perfectly fine, with the Swiss bunch assuming a hands-off attitude and letting the capable Alan Hale run Celestron. More—and not always favorable—changes were soon making themselves felt, however.

The first of which was the coming of the first real competitor Celestron had faced. Another California telescope company that, like Celestron, was the dream of a starry eyed engineer. For more on the story of the coming of John Diebel’s Meade, I’ll, if’n you don’t mind a little book plugging, refer you to my Choosing and Using a New CAT. For now, it’s enough for you to know that Diebel brought forth an SCT that was not only as good as a C8 (after a little tweaking); in some ways it was better. Celestron did react, though it took a while, leadin’ me to believe they’d been blindsided by Meade to some degree. When the dust settled, the Orange Tube C8 was gone. Celestron had a new and slightly more advanced scope, the Super C8, which soon evolved into the Super C8 Plus. Thus began the game of SCT one-upmanship that’s continued e’en to this day.

You’d a-thought Comet Halley woulda been great for Celestron, that it would have provided more than enough new telescope customers to make up for those Meade had siphoned off. And it did—for a while. What caused the Halley Debacle that troubled amateur astronomy and its premier telescope maker for at least another decade was Celestron’s overall strategy regarding the comet craze—or rather their lack of one.

What happened was Celestron decided to make hay while the Sun shone. Not a bad thing, maybe, if they’d kept their wits about them—and their quality up. They didn’t. Instead, Celestron began to kick SCTs out the door in ever-increasing numbers and to such an extent that they wore out not just their tools but their workforce. QA didn’t just suffer; by the height of the Halley madness, it went completely by the boards. That is why, younguns, you’ll hear us ol’ curmudgeons down to the club warn y’all off “Halleyscopes,” telescopes produced during the period when Celestron’s (and Meade’s) quality was at a low ebb, a period that went from about ’85 to ’90. Not that Celestron didn’t produce some good scopes and many average ones during that time, they did. But there were plenty of bow-wows.

Even more serious, Celestron made the wrong assumption. They assumed Comet Halley would create so many new amateur astronomers that they’d be able to continue selling at a breakneck pace. Uh-uh…nosir buddy. If you were around and in the astronomy game at the time, you are aware Comet Halley turned out to be a distinctly average comet for amateurs and a complete bust for the public. West had put on an incomparably better show a decade previous, and Hale-Bopp would do the same a decade later. Me? I was happy enough with what I had already known wouldn’t be a great appearance for Halley. The public?

Not So Much. Quite a few of the SCTs bought for Halley went right back to the dealers. Others went into closets and attics where they remain to this day. None of which is surprising, since I can’t think of a poorer-suited instrument for looking at a big, diffuse comet. Certainly, nobody was running out to buy new Celestrons (or Meades). In the wake of tons of Halley junk, ever’thing from comet coloring books to comet wine, the Bubbas and Bubettes on the street had had enough astronomy. Amateur astronomers? Even in those benighted times, the word got out—by word of mouth and by means of our little mimeographed club newsletters—don’t buy an SCT right now.

Which left Celestron where? Ah, muchachos, that is a story for next time...

Great article Unc!
So if I'm imagining this right, the focus mechanism on the original blue/white amounted to three spindles that supported the mirror, and these spindles were threaded into drums that were all connected by a toothed belt, like a Harley's "chain", and the focuser knob bit into this belt and caused all three drums to rotate and push the mirror back and forth.. and the spindles could be individually turned so that the primary's collimation could be set - sounds good and actually pretty simple - that would be a great selling point for a modern SCT..

Never have seen a blue/white but would love to own one some day..

Hey, what a great history. My father is the owner of a Celestron C8 prototype. He was asked to use it and give feed back on the scope prior to production. He would like to sell it would you know of any collectors that might be interested in it?
Thanks for posting the interesting stuff.

It is an informative article that contains some unique information. The fact that Celestron once made a 4" SCT came as a complete surprise to me.

Today no company makes a 4" SCT and the only affordable cats with that aperture are Maksutov's including Celestron's. It would be interesting to know why Celestron switched from the C-4 to the C-90.
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