04 Feb 2000 From: "Eastman, Jack F" Subject: Work of the Devil Once upon a time, long, long ago yours truly was engaged in helping Tom Johnson, then owner of Valor Electronics etc, fuss with a new and interesting telescope design. I ran into Tom at a LAAS star party where he showed up with an 18-inch Cassegrain. What a monster! Aperture fever in those days quit at 12.5" mainly due to a giant cost leap between the price of 12.5" ($21) and 16" ($175) mirror blanks This 18" telescope appeared on the cover of Sky & Tel for March 1963. Tom had read of the Schmidt Cassegrain telescope design, and its superior performance. He read, I think, Baker's paper, and the superior performance was the flat aberration free field of Baker's photographic telescope. The commercial SCs bear no resemblance to the Baker design. Tom began fiddling around with the Schmidt correcting plate and tried to figure out how to produce the nasty 4th order curve on that glass. His fiddling led to a serious breakthrough in the producibility of these correcting plates, and allowed for rapid quantity production of these things. Tom got the bright idea of trying to market the idea, and began advertising the "Celestronic 20" using his 18", now Schmidt Cassegrain, as a prototype. By now I was on the scene and we procured 22" blanks, to be edged to the 20" mirrors, and began the arduous task of figuring the master plates for the correctors. The mirror blanks came from Hayward Scientific Glass, and were nice and round with slightly tapered edges. They required no edging, and thus was born the Celestron 22. While we were building a couple of these monsters (One ended up at Tom's private observatory in Palos Verdes, One went to Beloit College. (replacing a 9" Alvan Clark) the other one came to the Museum of Natural History here in Denver) Tom thought of a couple of other designs for this telescope. One was a 10", f/2 primary f/13.5 overall, and we did a 4" f/3 - f/15 and a 6", I think it was f/2 - f15. (We later did both a 4" and 6" at about f/8 for photo use) Somewhere along the line, and this was before we had a production line going, Tom got the bright idea for the infamous 4" off axis. The parent system was a 12" f/1 primary [Kiss of Death #1] and, I think, an 8X secondary magnification.[Kiss of Death #2] We had off axis mirror blanks cast (they looked like horse's hoofs) and began to make the master for the 12" correctors which would be "cookie cut" to the 4" aperture. The corrector blanks couldn't take the "bend" and invariably broke at the 70% zone. This was solved by grinding and figuring half the correction on the plate, then flipping it over on another master for the remainder of the correction. [Kiss of Death #3, getting the two sides centered to what no doubt oughtta be small numbers of wavelengths of green light] One of the 'nifty ideas' was that the finder was a 30mm(?) aperture f/7 (It may have been a 50mm aperture) coaxial with the axis of the main telescope, which worked at something like f/21. The scene brightness from the finder swamped the main telescope, so when the object was centered a shutter was flipped down in front of the lens, and the light from the main telescope reached the eyepiece. For bright, small objects, like Jupiter, one could see both the finder and main image at the same time. Well, we make a couple of sets of optics and some tube parts and all and build one of these beasts. It was a serious bear to align and collimate. [Kisses of Death #4,5,6,7,8,...N, well you get the idea] Not only were there the usual degrees of freedom (tilt of the Primary and Secondary mirrors, Decenter of the Secondary and Corrector) but now there was rotation around the aperture for both the primary and corrector, and the beam walked across the secondary as the spacing was changed for focusing. I don't recall if we moved the mirror spacing on this thing for focus or not. To what tolerances to these adjustments need to be made and maintained? You don't want to know! And I really don't, but if someone suggested angles to arc seconds and displacements to small numbers of wavelengths of light I wouldn't argue. I did a tilt and decenter for the ubiquitous C-8, and to maintain 1/4 wave, decenters of the secondary or corrector came out the order of +/- 2um. That's 4 waves of visible light!!, and the C-8 is really benign compared to this system! I seem to remember, that as the C-8 mirror spacing is changed (for focusing) it takes only a couple of millimeters before you have 1/4 wave of spherical aberration. I need to rerun those calculations. We assembled one of these beasts and it took Tom and I almost all day to tweak it up on the bench. Tom took it home that night, and said it gave satisfactory images of Saturn, but only after considerably more tweaking. It needed to be heavily tweaked again the next morning back on the bench. This little pig was sensitive to everything, maybe even the position of Charon relative to Pluto! If I had known then what I know now, and had access to GENII or ZEMAX a couple hours of analysis would have put the nails in this thing's coffin once and for all. Now that I think about it, maybe I'll try a ZEMAX model of this thing! But not 'till I've had several margaritas. Along about this time we received our first, or nearly the first, order for one of the "table Top Tens" A gracious little old lady wanted to get a very good telescope for her grandchild for a graduation present. She ordered a 10". Meanwhile we had sent our ad photo copy to Sky & Tel for the next issue, with text to follow shortly The ad included a 10", 6" 4" and "the beast" When we determined "the Beast" was unbuildable it was too late to pull the photo if we wanted to make the upcoming issue of S&T Oh what to do?? Tom had a stroke of genius. We'll price the damned thing out of existence, so when we sent the text to S&T we priced "The Beast" at 5- or 6 times that of the 10. Good, that ought to kill it, and we'll pull it for the next and all following months. Dead! Good! End of problem! Not so fast!?! Remember the little old lady? She apparently got wind of our insane price, and thought "More money, must be better" and changed her order accordingly. Oh #$(words you don't hear in Church)@#. It took heroic convincing and cajoling, even the bald faced admission that this was an experiment, and no! really, we couldn't build one at ANY price, before she reluctantly went back to the 10" Whew! There is a lesson here, something about test it before you fly it, maybe...(Hey, Mars '01 guys! Are you listening??) Anyhow that's the saga of a ghastly little telescope as I think I remember it. Cheers, FJE ---- 21 Feb 2000 As suspected, there's more. While sitting around the library at Chamberlin, after last Friday's meeting, some of us were rooting around in the old Sky & Tel.s. Sure enough, that ad I had referred to was in April, 1965, p249. It showed the "table top Ten", the 6", on its pier mount, the 22", with Tom Johnson standing next to it, and "The Beast". From that photo, it looks like there is a knob on the back for moving the primary mirror for focus. A small lever can be seen near the finder's objective, this for the shutter used to close off the finder after locating the target. The secondary magnification was apparently 8.333X. (Even worse than the 8X!) In your initial question, you mentioned a couple of prices (?). Those, it turns out, were for the 10" ($1670) and "the beast" ($2600) I had thought we priced the 4"OA much higher than that, in the effort to kill it. Apparently not. While poking through that issue, another ghost from the past came up, Eastmann Optical of Manhattan Beach. (same issue, p 246) That is a story in itself, of literally sniffing out a fellow telescope maker, followed by many years of a wonderful relationship and it turning sour. The nutshell version follows. One night while observing with some friends in our backyard, in Manhattan Beach, we thought we smelled the unmistakable odor of cooking optical pitch. We lived about a mile South of the Standard Oil refinery in El Segundo (renamed El Stinko, due to that refinery) We'd get the stink if the wind was out of the North. This particular evening we really thought the smell was optical pitch. We began walking North and after a few blocks we saw, through an open garage door, someone setting about to pour a polishing lap for a huge 10" (it may have been a 12.5") mirror. We (we were all still in high school at the time, a 6" was standard, an 8" considered big.) introduced ourselves, and so began a wonderful friendship. Elmer would seemingly do anything to help us bunch of brats, and after the umteenth time I asked for help making some little part, he said you've seen me do this enough times, go out to my shop and make it yourself, and so I learned to run his lathe. My parent's probably were sorry this ever happened as they got no rest until I had my own lathe, drill press mill etc. Over time we did acquire everything but a mill. Elmer is the "benevolent neighbor" I mentioned in my article on the 12.5" reflector. Time passes, I am about ready to graduate from UCLA, and the army was breathing heavily down my neck. Elmer was thinking of producing a small telescope commercially. He asked if I had any objections if he used the name Eastman Optical, no doubt trying to capitalize on Kodak's fame and fortune. At first I thought not really, but who knows? I may want to go into the business myself, and I'd sure like to use my own name, so I said I'd rather you not, for those reasons. My dad, however, had more serious concerns. I was fairly well known by this time in amateur astronomy/telescope making circles, and my dad reasoned if for any reason Elmer screwed up, what Eastman in Manhattan Beach would 'they' come after. He (my dad) said not only "no" but "hell no". Elmer did it anyhow, using two "n"s. Unfortunately after that, the relation with Elmer went downhill, there were to come other disputes (Elmer was also our insurance agent) Ill health? alcohol? Family problems? who knows. Eastmann Optical, mercifully, did not last and we never had any heartburn from it. >From the "old History" brain cells... FJE