Criterion Dynamax 8 Schmidt Cassegrain Telescope
Posted 07 May 2017 - 01:15 PM
Isn't it a beautiful world! Everyone is entitled to there opinion, I can only speak from personal experience. I was never fortunate enough to have had the wealth it took to buy a large wonderful telescope such as a Orange Tube Celestron C-8 or Dynamax 8. I am sure I would have been in love with either offering. I had only owned a few (1970's) Sears Discoverers and a 4 1/2" Tasco Reflector which are collectable and somewhat respected today. Of course they were department store junk then. excessive useless magnification, etc. Of course some of this low priced garbage made of plastic today does make us old guys see things in a different light. I learned so much from the use of those Sears and early Tasco scopes and enjoyed them so much, I saw so much with such small apertures. don't get me wrong I own a few modern scopes with plastic parts made in China with computerized mounts and they have come a long way and are very very nice.
Today is a different matter. I have a huge hoard of vintage telescopes of many different sizes and shapes I have an SPC8 and a Powerstar C-8. the SPC8 was purchased in the 1980 during the Halley Craze. The optics were about average for the time, one of the astro magazines did a review of the Celestron C-8. Even with there conflict of interest ( Celestron advertising in the magazine) they pronounced the optics having a rough figure and the optics were just fair. I never owned the orange tube scopes, or a Dyna-max can't voice an opinion.
I will not base my opinion on what I have heard second hand, I do own a Bausch & Lomb 8000 early eighties I purchased it from a guy on Craigslist, it was from sunny southern California and arrived in the huge box on my porch about 10 years ago. My first impression was this thing is built like a two ton truck. I did a lot of cleaning checked if everything was OK. The dry climate and attic it was stored in had been good for the mirror coatings, just a slight dusting very nice overall. Upon setting up the and some playing around and checking out the smoothness and feel of the controls and the feel and stability of the drive base and fork bearings really surprised me, solid and very smooth movements. I read something about spindly shaky undersized forks, not so on the B&L 8000 built like a truck can't speak for the dynamax.
Under the stars first light was slightly disappointing, fuzzy out of focus stars. I let the scope cool down longer it yielded some improvement. I decided to aim the scope at Vega and check the inside and outside of focus patterns, the optics were out of colimination. I removed the corrector blew out all the dust inside installed it back into the OTA. The next clear night set up with the tools needed to colliminate the optics, several hours later they were as close as I could get them in the field. What a difference it blew the old SPC8 optical tube away. The optics seemed to snap into focus, bright clear images.
The Golden Pyramid Tripod was ahead of its time mine was clearly label Criterion Scientific Instruments but had the Black Plastic coating on the cast parts. The Tripod is very heavy duty and solid, I soon found the lack of a wedge was the weak spot on the mount. The hinge design with the cast bars that attached by hardware on each side to set the latitude of the observing site. I found that this caused the only shake in the mount and forks. later B&L remedied the situation and put a standard wedge on top of the tripod and it was solved. I found that by adding serrated washers under the knobs that locked it in place I could get it to stabilize and stay at the right latitude.
Awhile later I attended an estate sale in a waterfront home. In an upstairs room sat a late 80's Powerstar C-8. The scope came with every accessory ever made and had a slew of high end eyepieces (for the 80's). it was complete with a norton star atlas and so much stuff. all for $300.00, how could I walk away? After getting it home I noticed how much lighter the scope seemed compared to the B&L 8000 It was built much lighter than the 8000 which made it easier to haul around. But it was not built like a truck, so much for the supposed spindly forks on the B&L misinformation I had read. The forks and drive base were lighter and The slow motion actions felt sloppy compared the action on the B&L 8000, I think it is the extra mass and tighter tolerances.
Under the stars the optics were a total wash. It was obvious that the colimination was way out. when I got the OTA in the house I noticed I could grab the secondary holder and move it from side to side in the corrector plate, seems the wonderful folks at Celestron used a glue to hold the baffle tube in place. It had broken down and let go. I had to remove the corrector plate, luckily there is plenty of information on the net on how to do this.The factory rotates them to the best orientation for performance, to make along story short I used shims and RTV Silicone and glued the the secondary baffle back in the exact center of the corrector plate replaced it into the OTA. The next clear night with tools in hand I used a star near the zenith to colliminate the secondary as well as could be done in the field. The optics in the late 80's-90's C-8 OTA were wonderful clear and sharp. The dry storage had preserved the special coatings.Things would snap into focus. It was nothing like the OTA that came with the SPC8.
I have a B&L 8001 I will talk about it another time. The point I am trying to make is all of the companies at the time were hit and miss on optics. There is a lot of misinformation out there, and I had a friend who said this and that. I looked thru one at a star party it was garbage. I chose not to listen to everything I read. When buying vintage equipment of any brand name, you should check them out before buying them. Expect to make some adjustments. I am positive that Criterion, Celestron, and Meade have some wonderful vintage scopes out, there is some garbage. But don't pass up a second hand scope because you heard they were the scourge of the earth in optics. Find Out For Yourself. You might be pleasantly surprised! If you can't afford the latest and greatest so what enjoy the hobby.
Maybe I will do a review on my 1987 Questar i found on craigslist for $400.00 recently.
- Herr Mario, Karl Fabian and Gil V like this
Posted 22 March 2018 - 06:18 PM
I recently was considering buying one of these Dynamax 8 Schmidt Cassegrain until I came across this article. Thank God for the Internet and Cloudynights, As I read through the article I realized everything mentioned regarding a perfect storm was in fact the reality of my experience . The truth is when I first saw it I was going to buy it based on looks alone. I thought the controls and the table wedge and even the color gave me the opinion of old time quality . Yet as hard as I tried I could not get it to focus or stop moving the fork was like a tuning fork . I passed on the deal and ended up buying a 10" meade classic Schmidt Cassegrain . I no longer wonder if it was my eyes that was the problem because I'm seeing things really clear now.
- highfnum and Herr Mario like this
Posted 28 March 2018 - 04:57 AM
I still have my dx8
Because its infamous
But I use my mak7 c925 and c11
More often now
But once in a while I take dy8 out
It's old sync drive still works
Rest of scope is great
But that corrector plate
Problem hurt rep