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Criterion DynaMax 8

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#26 JohnnieS

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Posted 12 August 2021 - 05:21 PM

I bought one new in 1977 it came with the shower cap cover from the factory



#27 Stevegeo

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Posted 13 August 2021 - 07:30 AM

Must be the DELUX. Model ....lol ..


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#28 CltFlyboy

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Posted 13 August 2021 - 08:16 AM

Heck, I’ve had two classic orange tube C8s, a 1977 and a 1983? IIRC, and neither were anything special. 

The C8 I have came from a friend who got it back in the late 70's or early 80's. It had sat unused until two years ago when I asked if I could borrow it. The corrector was badly fogged, and the mirror had a fair amount of spotting too. I carefully cleaned it up and rebuilt it. I've got to say that it has some of the most impressive, tack sharp views from any C8 I've used - he got lucky with getting a good one. Now I just need to get it back to him so he can enjoy it. Putting it on that Meade field tripod without the wedge was one of the smarter things I did - you can easily carry it out as a package and use it for visual in alt-az mode, or if  you want to track, simply raise the base to the right latitude and you're in biz. 

 

My ploy to "borrow" it was so that I could get it functional for his enjoyment - mission accomplished.


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#29 kansas skies

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Posted 13 August 2021 - 11:45 PM

Although I've never had the opportunity to use a B&L DynaMax 8, I do have some experience with a Criterion 4000. As I remember, although it was possible to focus the scope easily, the image presented was akin to trying to observe through a window screen - very soft and not well defined at all. It really was not a pleasant scope to use. That being said, I'm a huge fan of both Celestron and Meade SCT's. I've owned two C8's, one being a 1984 black Super C8 (that I purchased new) and the other being a second-hand 1978 orange tube, which I still own. The Super C8 had optics to die for - absolutely perfect. I spent many, many hours with my eye glued to the eyepiece of that scope and was always very satisfied with its performance. I owned it for about eight years, and only sold it due to the financial difficulties I was having at that time. Letting it go was definitely a low point in my life.

 

I've owned my 1978 C8 for a little over eight years now, and although I don't think the optics are quite as good as those of the Super C8, they're not far behind. Whether they're 1/4 wave, 1/2 wave, 1/20 wave, or even a whole wave is completely irrelevant to me, as the scope's optics far exceed my expectations for image quality. My main criteria for acceptance is that the visual image delivered by any of my scopes is sharp and clear at 50D under perfect conditions. For a C8, that's only 400x. Both of my C8's easily went to 566x with no image breakdown. The planets would begin to dim quite a bit, but the image held true. The only problem is that there just aren't that many nights around here that allow for pushing a scope that far. Generally, 240x to 320x is a reasonable upper limit.

 

My 12" Meade has optics that are similar to my old Super C8. This is probably due more to the coatings, since the orange tube is not coated at all of which I'm aware. At 600x on Mars, Jupiter, or Saturn, the 12" is simply magical.

 

All this being said, I do understand why people have issues with SCT's, and I fully realize they're not for everyone. They're a royal pain to thermally stabilize, and this can literally take hours to accomplish. On some nights, the temperature changes so fast that the optics never catch up. Prior to settling down, the image suffers. A defocused star usually exhibits a waterfall effect during this period, and until that disappears, the image will not be stable. Under these conditions, the first diffraction ring has a tendency to dance like crazy as well. It's my understanding that this is due to the thermal boundary layer on the surface of the primary mirror. Until this settles down, close doubles tend to be a wash-out. Only after the scope adjusts to temperature can an assessment be made of seeing conditions. If the seeing conditions permit, collimation needs to be tested. Perfect collimation is a must with an SCT to ensure maximum performance. In my opinion, thermal issues are the biggest problem related to an SCT. While still just as relevant with a Maksutov, they tend to be a little more problematic with an SCT.

 

Speaking of Mak's, I owned a 7" Meade Mak for a couple of years, and found its performance to be very close to that of the C8. For that reason, I decided I didn't need both. After a few nights of comparison and evaluation of the optics, I decided the C8 had a slight edge in performance, so I let the Mak go. Although I really liked the Mak, I still don't regret this decision.

 

I only offer this information in the hopes that anyone interested in acquiring an SCT is not discouraged by some of the more negative reviews. From my experience, if one sticks to Celestron and Meade, while avoiding the few Halley years, most of these scopes are capable of exceeding ones expectations when given a proper chance. And, if you find that the SCT is not the scope for you, they tend to be fairly easy to sell. In my opinion, they offer a lot of scope in a fairly small package.

 

Bill


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#30 Terra Nova

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Posted 14 August 2021 - 09:10 AM

The C8 I have came from a friend who got it back in the late 70's or early 80's. It had sat unused until two years ago when I asked if I could borrow it. The corrector was badly fogged, and the mirror had a fair amount of spotting too. I carefully cleaned it up and rebuilt it. I've got to say that it has some of the most impressive, tack sharp views from any C8 I've used - he got lucky with getting a good one. Now I just need to get it back to him so he can enjoy it. Putting it on that Meade field tripod without the wedge was one of the smarter things I did - you can easily carry it out as a package and use it for visual in alt-az mode, or if  you want to track, simply raise the base to the right latitude and you're in biz. 

 

My ploy to "borrow" it was so that I could get it functional for his enjoyment - mission accomplished.

I think there’s a lot of variation in the optical quality of the orange tube USA-made C8s. Unfortunately much more so than the current Synta crop which, from all accounts is consistently good. My brother’s early ‘90s C9.25 is without a doubt the best of any Celestron SCT I’ve ever looked thru. Simply superb, refractor-like views.


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#31 highfnum

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Posted 14 August 2021 - 02:03 PM

c925 one of my favorite scopes at least of the SCT types


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#32 rcwolpert

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Posted 14 August 2021 - 04:28 PM

c925 one of my favorite scopes at least of the SCT types

Mine too.


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#33 Neptune

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Posted 01 October 2022 - 08:56 AM

I was interested in this topic as I have a chance to acquire a Criterion Dynamax 8 in near mint condition complete with drive corrector, camera adapters, finder scope, wedge, tripod, 6 Criterion eyepieces & case.  It looks so good!  Owner wants $400 for the whole package. A metal tag on the base, serial number 4027.  Strangely enough, I do not see a lens cap with it.

 

I have always liked the look of this scope.  It is as everyone else has said, futuristic looking.   I had many chances to purchase one of these back in the day.  In 1977, I  choose for my first real scope, a C-8. Even though I was a newbie, I believe it had just average optics, but boy did I have fun with that scope!

 

I have read all the reviews on the Criterion Dynamax 8.  It's just heart breaking.  I wanted it to be optically as nice as it was to look at.  It's just so disappointing.  If I wasn't married I would purchase it just to let it sit in the living room corner with a pin spot light shining on it, to be gazed upon like a piece of art work in a museum.

Attached Thumbnails

  • Criterion Dynamax 8 .jpeg

Edited by Neptune, 01 October 2022 - 08:59 AM.

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#34 Terra Nova

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Posted 02 October 2022 - 06:39 PM

They are very pretty pieces of astro art. Instruments, unfortunate they are not.


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#35 photoracer18

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Posted 05 October 2022 - 04:37 PM

Yes I agree 100%  on your statement ...

 

   " If you setup a DX-8 next to a telescope of the same aperture and use a magnification of over 100x  but with true 1/8 wave optics while observing say Jupiter  you will see the difference. The image will be like the picture quality  in an old analogy TV picture in the DX-8 vs a modern HD picture in the scope with the true 1/8 wave optics. Many need to see a side by side view to see what they are missing."

 

A side by side test is needed ,   I would like to see an orange C8, black C8, Meade 8 and Dynamax 8., maybe a few more ..against each other ,  a shootout of the 8's....  bring it on!!

 

Fully collimated  each  of course ..

 

Is this a challenge? 

Not really. There are people on this forum who used to work for Criterion and then B&L building their scopes. I was an early RV-6 owner, but my first SCT was an early C8 so I never tried the Dynamax 8 until I had already found out about the corrector plate issue. But I bought one cheap just to have it a couple of years ago off CL.


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#36 luxo II

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Posted 06 October 2022 - 05:44 AM

A side by side test is needed ,   I would like to see an orange C8, black C8, Meade 8 and Dynamax 8., maybe a few more ..against each other ,  a shootout of the 8's....  bring it on!!

 

Fully collimated  each  of course ..

 

Is this a challenge? 

A neighbour has a DX8 and a while back I thought I had succeeded in persuading him to bring it out and setup. Until he had a look at Saturn through my scope, after which he politely declined to set his up, which I think says enough, and I don't ask.

 

OTOH There's a set of Meade ACF optics up for grabs on AM, and I'm wondering if they could be transplanted into either an old Meade 2080 or a DX8 OTA.


Edited by luxo II, 06 October 2022 - 05:46 AM.


#37 davidc135

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Posted 06 October 2022 - 02:01 PM

The DX-8's primary is a little slower and the OTA longer than a Meade or Celestron and so some surgery would be needed.

 

David


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#38 Goofyboy1

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Posted 14 August 2023 - 05:59 AM

Hello everyone,

 

a few days ago I bought the Dynamax 8” because my eyes felt on the case with all the optics and color filters and 90 degree piece. I paid €200,- for the tripod, case with filters, oculars and more and the scope. 
 

now I’m wondering how I can restoration this scope the best way. The tube is loose from the base and was glued with silicone and that is in my opinion the best way… now I’m looking for information how too restoration this scope en optics and how to clean them.

 

I read everywhere that the optic is terrible and I’m wondering if it’s possible too reshape it and give it an new coating so it’s will performance as good as possible.

 

how can help me?

 

kind regards


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#39 davidc135

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Posted 14 August 2023 - 10:31 AM

Hello everyone,

 

a few days ago I bought the Dynamax 8” because my eyes felt on the case with all the optics and color filters and 90 degree piece. I paid €200,- for the tripod, case with filters, oculars and more and the scope. 
 

now I’m wondering how I can restoration this scope the best way. The tube is loose from the base and was glued with silicone and that is in my opinion the best way… now I’m looking for information how too restoration this scope en optics and how to clean them.

 

I read everywhere that the optic is terrible and I’m wondering if it’s possible too reshape it and give it an new coating so it’s will performance as good as possible.

 

how can help me?

 

kind regards

Do you have any photos?

 

I'd test it out at low, medium and then high power before removing anything.

 

The corrector plus 2ndry can be removed and the corrector plate cleaned with acetone then soapy water, finally pure water. I doubt if there are any coatings on the plate, hopefully the mirrors are in good shape.

 

Most of the optics problems are usually due to the poorly made corrector plates which unfortunately can't feasibly be improved. It would be better to start from scratch but it's a really tough one.

 

David


Edited by davidc135, 14 August 2023 - 10:35 AM.

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#40 Sketcher

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Posted 15 August 2023 - 11:33 PM

I bought one new in 1977 it came with the shower cap cover from the factory

What a coincidence!  I bought mine new in 1977 -- and yes, it came with the shower cap cover as well.

 

I didn't part with my Dynamax-8 until 1995.  Sometime prior to that I also had a 10-inch Newtonian that was better at everything visually; but not as portable as the D-8 and not as practical for (old-fashioned) astrophotography and outreach with school students.

 

The optics in mine were not very good, especially when it came to planetary use; but it was still a telescope that got a great deal of serious visual use.

 

Shortly after the telescope purchase, I ordered the Criterion Golden-Pyramid tripod -- and that I still have!  That tripod has been used with multiple telescopes and has even been used for a few non-traditional (non-astronomical) purposes.

 

Even though the optical quality of my D-8 wasn't all that great, it was still a functional telescope.  I used mine to photograph the February 26, 1979 total solar eclipse.  My photos turned out so well that after seeing them, a photo lab rejected the photos taken by a friend (who used a 3.5-inch Questar) in favor of mine to reproduce and sell to the general public even though they had previously agreed to sell the Questar photos -- until they saw my photos.  Of course, this wasn't because the D-8 was better than the Questar, but more due to the photographers and to their different choices in film.

 

I used a fine-grained color slide film (Kodachrome 64).  The lab sent my slides to a custom lab to make a set of large-format negatives that were then used to make prints of various sizes up to 11x14 inch.  I still have the original slides, the large negatives, and some of the prints.

 

My friend had used a coarser-grained 400 speed film.

 

I combined the features captured in some of my photos (I used a large range of exposure settings) into a single painting where I tried to accurately depict the corona's structure as well as the prominences -- along the sun's eastern limb when they were at their best and along the western limb when those were at their best:

 

Totality Feb26 1979 Sketcher

 

I've never let poorer quality optics get in the way of making the most of a telescope!


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#41 Astrogeordie

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Posted 16 August 2023 - 05:21 AM

Nice to read about this instrument.

 

I got one a few years ago, but it was the later version of Bausch and Lomb, called "8000 professional". I did some intensive maintenance on it, and I have lots of images of dismantling the tube and the mount. I had to get the secondary re-coated. Optically this instrument is quite good and far superior of the two Bausch & Lomb model 4000s I have (102/1200mm). I made a 2" adapter to replace this really stupid diagonal which bears a tiny prism and vignets any wide field eyepiece, so now I can use a 2" diagonal. I put it onto a wedge I purchased 2nd hand (you can see it in the 2nd picture, no clue which brand this is) and adapted it to a Sky-Watcher EQ6 tripod. In this configuration it is my telescope for outreach and star parties. Just tomorrow I will take it to Dalby Starfest here in the UK.

 

Apparently, after Bausch&Lomb took Dynamax over, the quality issues have been fixed and some really nice instruments got delivered. This was also when the rare 6" version appeared (model 6000). Sadly, shortly after the production of all of those discontinued.

 

I was surprised by the fork, which with its lattice work looks flimsy. It is quite a solid casting and for all it still swings, it seems more stable than the Celestron 8 version.

 

1_cindy_before_small.jpg

 

IMG_0815_small.jpg


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#42 Bomber Bob

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Posted 16 August 2023 - 02:04 PM

I coulda / shoulda called my 1974 DX8 The Heart-Breaker!  One beautiful Classic Rig:

 

DX8 - Golden Pyramid Tripod S01.jpg

 

Excellent mechanicals, Questar-like axes + instant grip clock drive...  BUT... the awful Corrector made it a niche scope, suited to faint fuzzies only...


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#43 pyrasanth

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Posted 20 August 2023 - 05:40 AM

I was really fond of my Dynamax 8 but was forced to sell it in my youth due to too much spending and not enough common sense with finances.

 

I had some very nice views of star clusters and since I did not know the difference between good or bad optics at that time I don't know if I had a good or bad example.

 

I did manage to blow up the PSU by plugging the power connector in backward- it was really badly keyed and could be plugged in either way.

 

I opened up the control box to look at the connections and it looked like it had be soldered by an Elephant- there were great big blobs of solder everyehere- some of the worst electronic assembly I'd seen as I was an RAF technician at the time.

 

The golden tripod was nice & solid and those sharp feet really stuck into soft ground really well. 

 

I guess I have a great sentimental attachment to my old D8- I hope the new buyer loved it as much as me.

 

Here is a picture of the old love from a previous post https://www.cloudyni...es/?hl=+dynamax


Edited by pyrasanth, 20 August 2023 - 05:52 AM.


#44 Gil V

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Posted 20 August 2023 - 07:45 AM

Good to read about my favorite telescope once in a while.
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#45 DAVIDG

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Posted 21 August 2023 - 11:13 AM

 I was at Stellafane this weekend and got 3 more Dx-8 correctors from  the person that bought out what was left of Criterion when they closed. I'm going to test them and maybe there is good one in this batch or one that won't take much to clean up, in my quest to have an optically excellent DX-8

 

                - Dave 

 

dx8 correctors.jpg


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#46 Gil V

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Posted 21 August 2023 - 12:07 PM

Good luck with those correctors! I can’t remember the last time I saw three of those in one place like that.

The one marked “small” - if the OD was cut incorrectly - it would be really interesting to figure out how to install it.

#47 Piggyback

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Posted 21 August 2023 - 12:18 PM

Criterion Dynamax 8 ATT Essen 2019_01red.jpg

 

I was tempted to buy this one. Offered at an astronomy trade fair in Germany I still kick myself for not jumping. Looked brand new.


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#48 DAVIDG

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Posted 21 August 2023 - 12:32 PM

Good luck with those correctors! I can’t remember the last time I saw three of those in one place like that.

The one marked “small” - if the OD was cut incorrectly - it would be really interesting to figure out how to install it.

 Hi Gil,

   The one marked "small" maybe a 1/16" of  an inch  smaller in diameter then rest so if it happens to be good I don't see a problem mounting it .

   The person I purchased them from had a case full of them. I asked about the figure on the secondaries and he wasn't  sure what they were. He said they came stuck down to sheets of cardboard and they would peel one off and try it and if it didn't work pitch it and try another. 

  If they were spherical they should have been pretty consistent in their figure but as I suspect they were aspheric and that would account for the variability in their performance.

   I'll report soon what I find with these new ones.

               - Dave 


Edited by DAVIDG, 21 August 2023 - 12:33 PM.

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#49 Gil V

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Posted 22 August 2023 - 07:58 AM

I wonder if we could arrange to go through all of RP’s inventory and find the “good one”. 😂😂

Chances are they’re all pretty similar in that they will vary considerably without any being particularly good.

Edited by Gil V, 22 August 2023 - 07:59 AM.

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#50 Gil V

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Posted 22 August 2023 - 08:03 AM

When I built the telescope, the secondaries arrived in boxes of maybe 10, fully coated. Imported from Japan.

I glued all of them to the secondary block with rubber cement sandwiching a cork disc. When assembling, I rarely came across an unusable secondary.

If B+L changed suppliers, all bets are off in what they are like as far as consistency.


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