- The Ages of Astrophotography 1839-2015
- Stardust Gallery LED Lightbox and Metallic Print Review
- Rayox Saddle Review
- MoonLite NiteCrawler Focuser
- Celestron Cometron 7x50s Review
- Astro-Devices (of Ukraine) Parallelogram Standard II Pro
- Review: Explore Scientific 16”, Europe edition, late 2016
- VITE 2X Barlow Lens Review
- Sky Commander Review
- Wireless Control of Canon EOS DSLRs with DSLR Controller and TP-Link MR3040 W...
- Review of the 18” f/5 Otte binodobson
- Wireless Telescope Control for Celestron (and Compatible) Scopes
- A Review of Teeter STS18
- MesuMount 200 Review
- First Light with the Prototype 8x42 Space WalkerTM 3D Binoculars
CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.
Discuss this article in our forums
by Gil Violette
There was a time in my life, many years ago, when I worked for a telescope company. I was a telescope enthusiast at the time, one of my early obsessions in a life of serial obsession.
The company was Criterion Manufacturing, a small family owned company in West Hartford, Connecticut.
It was a stroke of luck that Criterion was in my backyard. At that time, there were only four telescope making firms in the United States. One was in New Jersey, and two were in California. I didn't realize how lucky I was.
I do now.
This is the story of my time at Criterion.
Ever since I was a kid, I've had an interest in telescopes. I bought my first telescope while still in high school, it was a 4-1/4" f/10 Newtonian from Edmund Scientific. It was my first experience with a German equatorial mount - something I would get to know a lot better at Criterion.
When I bought the scope from Edmund, I ordered it COD - cash on delivery. When the scope arrived, they asked for $10. I gave them the cash. The scope price was $160, so after a couple of days, I sent Edmund a check for the price of the scope. They returned the check, saying it was a duplicate payment. Lucky me!
One night, I was set up to see a close Jupiter-Mars conjunction. It was an early morning event, and I had to set up halfway down our street to get a clear view. I was on the sidewalk in front of our neighbor's property. The planets were so close, they were in the same telescopic field of view - a rare event.
While I was out there, two cops stopped by. I showed them the planets and the moon, and one of the cops told me his theory about UFO's. A memorable evening for a teenager in the 1970's!
After high school, I was working full time and living with my parents. Lots of cash and no expenses. I sold the Edmund scope to a friend, and bought an RV-6 from Criterion. I picked it up at the factory in West Hartford. It was a good scope, but I don't recall any noteworthy observations - at least none with police involvement. I was working third shift at the time, so I really didn't spend any time observing with the RV-6.
I also owned an Edmund Astroscan in the late 1970's. It was a good little scope, but is unusable without a finder, which they later added.
It was with those two telescopes that I watched the Venus occultation by the Moon on a cold winter's morning in 1978.
I don't remember if I saw an advertisement for an opening at Criterion, but I do remember giving them my application. Somehow, they hired me, and I put in my two week's notice at my night shift job.
I didn't own a car yet, so I had to ride a bus from East Hartford to Hartford, and then catch a second bus to the plant in West Hartford. It sounds inconvenient, but it really wasn't - the trip was only 30-40 minutes each way. Connecticut Transit was (and still is) a very good public transportation company.
I was a 19 year old factory worker, and I was working at Criterion Manufacturing, a family-owned telescope company in West Hartford, Connecticut. There were only a few scope making companies around, notably Cave, Celestron and Edmund Scientific.
I remember discussing a holiday weekend occultation when I went in to work, and besides one fellow in our machine shop, I was the only one at Criterion who saw the occultation. That is when I began to realize that everyone else who worked at Criterion was not as obsessed with their products as I was.
Later on, I shot a roll of 35mm film at the plant. The embedded photos in this document are in no particular order, as they were all taken on the same day. I was working as the lead assembler iin the Dynamax area on the day I took the photos.
The first photo is of the RV mount assembly line – my first job in the plant. The pedestals are on tables to the right, and the components are in baskets to the left. There were 21 stands, so 21 mounts could be built in a production run.The OTA's for the RV-6 were built on the tables on the far right hand side of the photograph. The optics department is behind the blue wall.
The table tennis table doubled a a poker table for the occasional lunch time game.
Prior to the table tennis table, there was just an empty place on the shop floor.
I would assemble the mounts every day for several months, doing the occasional optical tube assembly and packing all of the mounts that I built. All of the assemblers at Criterion packed their own products.
The next photo was taken from the same location on the floor, but facing in the opposite direction. The machine shop is partly in view. At Criterion, we machined most of our own parts, and our metal parts were made from cast aluminum.
We didn't make all of our parts. Several components were imported from Japan - primarily the Dynamax baffle tubes and secondary holder assembly, along with the secondary spider and holder for the RV-6. All of our knobs and gears were imported.
Criterion was a very small company. Two people built the RV line, three people built the Dynamax line. There were three machinists, and four or five in the optics shop. One man built all the Dynamax tripods. One shop foreman, an office manager, a couple of office staff, and the owners. That was it.
We really were just a bunch of kids at Criterion. We would hold company Olympic Games, with the staff competing at lunchtime in such events as foosball, table tennis and miniature golf. I actually became quite skilled at foosball and table tennis. One of our co-workers had lent me a full-sized foosball table, and it was in my parent’s basement. At that time, there were nightclubs in the city with foosball tables, and if you could play well enough, you could get time on the tables. I was always able to play at these clubs.
After a while, I moved over to the Dynamax mount assembly bench - a job I really enjoyed. That area is pictured in the next photo - barely. The blue bench on the extreme right hand side is where the Dynamax mounts were built. The green rack held our optics.
We would open up the boxes and mount all of the Dynamax optics on that ugly green cabinet. You can see some baffle tube assemblies on the left hand side of the background rack.
We ground and polished all of our own glass, with the exception of the Dynamax secondaries - those were purchased fully coated from Japan. All of the coating of our house glass was subcontracted.
While I worked in the Dynamax mount assembly area, I bought a Dynamax 8 at company cost - about $450. I remember the day that our optical assembler said he was building my scope. By this time, I owned a car, so I didn't have to lug the scope home on the bus.
The Dynamax telescope
A lot has been written about the Dynamax telescope, not all of it good. Some of the rumors about the line were the result of effective advertising by our competition, most notably the "cardboard tube" garbage. The RV tubes and the Dynamax tubes were made from the same material, purchased from the same vendor. Tough, lightweight, and easy to work with.
I've owned two Dynamax scopes, and I've looked through hundreds of them - mostly when I was one of the optical assemblers in the Dynamax area. We made some good scopes and some bad scopes, our small company was subject to variation in quality like every other factory in the world. If I were to buy a used Dynamax, I would insist on testing it visually, simply because I would be buying a 30 year old used compound telescope. There were many fine scopes made by the plant.
You can argue all day long about whether one thirty year old product was of a particular build quality, but it's a moot point. The staff at Criterion worked very hard. My perspective was different, however, since I was an enthusiast of their products (telescopes) in general. As an enthusiast, I can tell you that we built those scopes to the best of our ability, and we stood behind every product we shipped.
The Dynamax that I brought home with me worked pretty well, I got a lot of use out of it. I photographed a lunar eclipse at one-thirty in the morning, and went to work at the plant the next morning at seven o’clock.
I also had some outstanding views of Jupiter with that scope, and I was able to see Saturn’s backlit rings – those were surprisingly easy to see.
It was about that time that I moved into Dynamax optical assembly. After learning that assembly process, I could break down and reassemble the entire instrument – something that I’ve never forgotten.
The optical assembly of the Dynamax was pretty simple, you build the primary, install it, assemble corrector/secondary, install it, and then star test the instrument. Adjustments were made by rotating the corrector, and changing optical components if necessary. It would take from one to four hours to build one, and after you have an acceptable image, you cleaned the living hell out of it and lock everything in place. Two assembled scopes a day was a pretty good output, because there were a lot of little assembly operations that we all helped out with.
This was my assembly bench in the plant. It was as steady as a rock – until the local train ran by. I’d place a telescope mount with its empty tube up on that stack of cinder blocks, and assemble and install the optics. The 8” tube assembly you see was our artificial star – it was like looking through a telescope into another telescope – which had a laser shining directly into its eyepiece. It made an excellent artificial star.
Optics at Criterion
My understanding of the optical fabrication at Criterion is observational – I never worked in the department. I understood enough about telescopes to be able to figure out what was going on, but it would be a misstatement to say I was an active participant in the optics shop. I helped out with some operations from time to time, but we all did.
Our RV-6 blanks arrived, and we placed them in a modified Bridgeport-type machine. The workholder spun while the tool head was in motion, inside a thick steel tray. You wouldn’t want to be around this machine if it throws a piece.
That machine is pictured here.
After removal from this machine, the mirrors were edged in a steel bowl with an abrasive mixture. From there, the pieces went to a grinding room. If my memory is correct, the first grinding tool was made of metal. The pieces were held by a weighted moving arm, and the tool would spin while the piece was moving across the tool – all in a wet mixture of slurry and grinding particles.
The RV grinding room was kept totally separate from the polishing room – probably to prevent contamination by abrasive particles, and because of the larger number of pieces that were required for that line versus the Dynamax line.
In this next photo, the steel bowl that we used for grinding the edges of the machined glass is in the background, In the foreground are some of the grinding laps. RV-6 mirrors are in process in the rack on the right hand side.
When parts went into the polishing area, there were a number of similar pieces of machinery – weighted moving arms that moved the glass across a spinning pitch lap – all in a cerium oxide slurry. Correctors were polished in a large machine – the lap for the correctors was probably three feet across. The lap rotated, and the piece sat in between steel arms – vacuum sealed to a glass block.
The correctors were attached to a large glass block. The block had a piece which had a mirror-image figure of the aspheric lens, and was channeled to allow a vacuum seal. The corrector blank would be hammered into shape while a vacuum was drawn. Special lighting would allow the operators to see how well the glass was adhering to the tool. After mounting, the part would be polished. When polished and removed, the curve would be transferred to the polished side of the glass, and the mounted side would be flat.
The infamous lawsuit between Criterion and Celestron was about this method. We used an extra piece of glass in our tool, Celestron didn't. The lawsuit probably contributed to some of Criterion's difficulty, it had to be a financial drag on the small company, regardless of the outcome of the litigation.
In the foreground of the next photo, you can see some of the glass blocks for corrector fabrication. The polishing machine is in the background. On the left is a tube used for optical testing – it kept the air steady.
There are metal grinding laps for the correctors on the left foreground. On the right hand side is the polishing area for the primaries. You can see a lot of RV-6 primaries in process, and the polished pieces are quite different in appearance from the unpolished pieces.
After the correctors were polished, we would mount them in this modified drill press. The diamond tip would bore out the secondary opening in the corrector. (There was a time when I used the "doughnut holes" for poker chips in games with my friends). We would then use a rotating manual tool to cut off 1" from the outside diameter of the corrector plate - a risky operation. When done properly, you'd end up with a corrector plate with a deadly sharp outside diameter. One last edging took care of that, and voila' – an aspheric telescope lens!
The boring of the center hole, if not set up properly, could greatly affect optical quality of the scope. It is important to keep the optical center and the mechanical center the same while you are working the piece. Photo is of setup for 8” corrector.
The biggest quality issue I saw at the eyepiece manifested itself as scattered light at focus. It was intermittent, but we had to work with the material we had. Any astigmatism that we found was easily rotated-out during assembly.
The Dynamax 6 optics were unbelievable - they almost assembled themselves. All the Dynamax 6's leaving Criterion during my time had very good optics. We hardly ever built them, certainly we made many more 8" scopes.
The product had minor design changes going on all the time. Some were cosmetic, such as different color schemes. There were some that were functional, though. As an enthusiast, I had opinions about those kinds of changes.
Because of my unique circumstance of being a Dynamax owner and the product's lead assembler, I undertook the task of making my Dynamax 8 the perfect telescope. I literally hand picked every part. The primary was a non-standard thickness, and the corrector came from a scope that was returned to our factory. One look through that piece of glass, and I knew. It went into my scope the next day.
My role at Criterion changed as time passed. I started to get involved with customer support - specifically handling complaints about quality and offering technical advice. This would prove to be helpful years later, when looking to replace my Dynamax. Showing that I had no appreciation for anything, I had sold the scope, figuring that I could build myself another one at any time.
Criterion was changing for other reasons, too. The company was for sale. The owners of Criterion were having some business difficulty, readily apparent to the workforce (me) as reduced hours, a brief layoff, and the occasional rubber paycheck.
Bushnell, a division of Bausch and Lomb, bought our little family business.
After The Dynamax
I never liked the 4" Schmidt-Cassegrain. It was the worst of all possible scopes, too small for high power, and too slow for low power. Plus, you could never get your head under the thing. And, the finder scopes were useless. I did have a small role in the development. When we produced our first production corrector plate, they gave it to me for cutting it to final size. I cracked the piece when cutting the center hole – using the equipment pictured previously. It certainly wasn’t deliberate; I was as upset as the managers were. But it was a sign of things to come.
B+L had us change the design - making it completely black, and emphasizing visual appearance over visual performance. I never saw a 4" Schmidt leave that shop that had optics that were any better than fair. However, the OTA of the Criterion 4" was one of the best telephoto lenses available at the time.
I was transitioning to indirect labour, responsible for purchasing and inventory. I used an early version of Lotus for an inventory system, and it worked pretty well. But B+L operated with a degree of professionalism that I did not possess - at least not at that age.
The company purchased a CNC lathe – and this piece of equipment was used to fabricate almost all of the OTA of the 4” – along with many of the parts for the 6” and 8” line that were sourced from Japan. Scheduling this machine was one of my primary duties. I also had to purchase all the raw material that the machine consumed.
We started to make our own visual backs, and we always had a more difficult time with the threads on the homemade versions of the part. We also made the secondary holder, block and baffle for the 6” and 8”. Then, we started trying to make some big parts – namely the corrector plate cell for the 8”.
The Japanese version of the corrector plate cell held the plate in place with eight screws. It is instantly recognizable by the engraved lettering on the retaining ring face, along with the eight socket cap screws around the edge. The serial number on every corrector cell is the same, by the way. The in house version of the same part had a large threaded ring which screwed into the cell to hold the corrector – a design that is greatly inferior. Trying to use rotational force to lock a piece of glass in place – without it moving? Poor design. Unfortunately, design decisions were being made by people who had no experience (or interest) in amateur astronomy.
This is where the quality of the bigger scopes suffered – the parts we made in house were never a good substitute for the ones we sourced internationally. The major change that affected the 6” and 8” scopes were the in house fabrication of the baffle tube and slide, along with the corrector plate cell. The underlying cause of the quality issues could have been a result of poor engineering (raw material selection), poor programming, or both.
I would never see the Criterion 8000 or 6000 leave the factory. I would say that I give no regard to the opinion that the 8000 and 6000 scopes were of a better quality than the Dynamax 8 and 6 scopes. Too many design changes were made that affected the “assemble-ability” of the telescope, and all of these affected performance.
I was frustrated with the change in direction, so I asked if I could build a Dynamax 4 out of 100% scrap parts and keep it. They said yes, so I built a unique Dynamax 4. Even that scope only had fair optics. (The only thing noteworthy I saw with that scope were the comet impact sites on Jupiter in 1994. In the 4", the dark spots were just barely visible). I eventually sold that scope.
Within a year, the company moved the plant across the river to East Hartford. It was a beautiful building, but it didn't matter, because a month later, I was gone.
I had seen an advertisement for a job that looked just like mine. It was a blind ad, so I applied.
When they called me in to let me go, the B+L dude says, "You saw the ad, you responded to it."
So, I applied for a job that I already had, and I didn't get it. Lucky me!
A year later, B+L closed the business. I had the opportunity to visit the plant one last time – meeting with the fellow that replaced me. He told me that a small group of investors wanted to buy the business, but B+L declined their offer. Another former employee described throwing many Criterion 4000’s into a scrap bin.
One of my colleagues at Criterion bought a healthy part of the inventory, and he sold equipment at Stellafane for a number of years. He had a clever method – he tagged boxes that he wanted, and paid the scrap dealer for those boxes – doubling the scrap dealer’s money.
Telescopes after Criterion
My tiny DX-4 was my only telescope for a while, although I built two 12-1/2" reflectors over the years. (Sonotube good, truss bad).
I eventually sold the DX-4 and bought a 10" Meade Starfinder. Kind of like an RV-6's bigger brother. It has excellent optics and has worked well, but as the years have gone by, I always wanted my Dynamax back. I knew the likelihood of finding the exact scope I had was “remote”. I was reluctant to buy one sight-unseen, as I like to look through a 30 year old compound telescope before buying it.
From the time I left Criterion in 1985 until the fall of 2012, several things happened. Some of those things, like the invention of the Internet, are important to my story.
I had caught an article on a popular astronomy website about the Dynamax product line. In the article, the author mentions me by name because I helped him with his scope - while I was the Criterion customer support guy. The article was a few years old, but I asked the admins to forward my contact info. They do, and I begin a dialogue with the fellow. I have a few spare parts from 30 years ago, and this author had a scope that could use a couple.
Fast forward a year, and the author of the web article wants more parts for a scope he just bought. I half-jokingly suggest he sell me the scope, and I'll put the parts on myself. He agrees.
And, that's how I got my Dynamax 8 back. It was built at the time I was working in the Dynamax area, although I have no way of knowing what part of it that I built – mount or OTA. It's not the same customized one I owned before, but it's in fine shape and has good optics. No scattered light. I had just enough spare parts for a tune-up. Lucky me!
- Darren Drake, rolo, desertrefugee and 17 others like this