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3 Criterion Dynamax 8 scopes and B&L4000

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#1 Olivier Biot

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Posted 25 July 2010 - 10:02 AM

3 Criterion Dynamax 8 scopes and B&L4000

#2 David Knisely

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Posted 25 July 2010 - 12:51 PM

The reviewer stated:

Be wary of bandwagon trashing of certain scopes. Take everything with a grain of salt.

My 1983 B&L 4" has fine optics and outperformed a Meade 2045 in a side by side comparison. Both 4 " scopes. The difference was in the coatings. The B&L had better coatings. More extension on M42. Syrtis Major showed better in the B&L as well as a polar cap. Star clusters were brighter and sharper in the B&L than the Meade 4".


I am glad the reviewer got some good results, but truth be told, these Baush & Lomb 4 inchers were an irregular bunch with some OK and some definitely bad news. The quality control definitely took a nosedive late in B&L's production of SCTs. I had one brought to me that was outperformed by the owner's 2.4 inch "department store" refractor. It produced star images that were triangular at best with only a hint of diffraction structure despite repeated attempts at collimation. The finderscope was also marginal. On the larger B&L SCT's, most amateurs compared them with the earlier RV-6 and RV-8 Newtonians that Criterion had produced in the 1960's and 1970's. They sometimes found the 8 inch Dynamax SCTs to be somewhat wanting in optical performance when compared to the earlier Criterion products. I used a good one that the University of Nebraska had when we did public open house nights at Behlen Observatory. However, one time, we also brought out an older Criterion RV-6 (6 inch Newtonian) that UNL had, and the Newtonian outdid the 8 inch Dynamax. I never went back to bringing the Dynamax 8 inch scope along. Again, one can get a good Dynamax of B&L 4000 from time to time, but it is no "myth" that some are definitely worth staying away from. Clear skies to you.

#3 GeneT

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Posted 25 July 2010 - 01:11 PM

I owned the Dynamax 8. The views were terrible. I believe most of us expect a Schmidt-Cass to work well out of the box. The author was able to get his collimated, optics realigned, and working well with a lot of effort, and his own personal know how. I have bought 4 Celestron 8's (three for my grandchildren.) All of them worked perfectly right out of the box. The images were sharp in all four Celestrons with no collimation needed. If all that was amiss with the Dynamax 8s was collimation, and realignment of the optics, then the company should have built much better quality control into the assembly process, and double checked the telescopes before shipment.

#4 GaryJCarter

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Posted 25 July 2010 - 01:50 PM

I've owned two B&L 4000 OTAs. Optically speaking, they both were under performers. The visual back on the B&L 4000 is a unique thread size. My Celestron accessories will not fit.

#5 highfnum

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Posted 25 July 2010 - 05:10 PM

I got both a c8 and dx 8 I should do a side by side review
that said the c8 is the better of the two - BUT - I got some good views thru dx 8

if u look thru my gallery I got some dx 8 shots

here is link in


http://www.cloudynig...php?photo=20003

but I agree without criterion to meade/celestron adapter
criterion had odd size thread

#6 mcoren

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Posted 25 July 2010 - 06:31 PM

Thanks for the writeup. I bought a used DX8 in 1981 through a classified ad in the back of S&T and I held onto it for nearly 25 years. Optically it was never great despite my collimation efforts, so perhaps I got one that had a bad "final assembly" experience. I agree about the mechanics being quite good. The tripod was very stable (especially with VSPs), tracking was smooth and consistent, and focusing was also smooth with very little image shift.

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#7 Mark Swanson

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Posted 27 July 2010 - 11:18 PM

With regard to the different thread size on Dynamax scopes, it is true that modern Celestron visual backs do not thread in. I have an older celestron visual back from what time period I do not know that will thread in quite easily.

All 2" diagonals do thread in. I have used 2" diagonals from University Optics, William optics, and Celestron that thread into DX8 scopes. I would never try to put a 2" on a B&L 4". There would be no reason to because you would not be able to use the full field of view on that little scope because of the baffle tube.

I have an Agena Astro skylight dust seal that does thread into the back of the DX8 and any Celestron accessory will thread into that. This does not take much ingenuity to do.

My Celestron reducer-corrector f6.3 easily threads into the DX8.

Mark Swanson

#8 Mark Swanson

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Posted 27 July 2010 - 11:36 PM

You make a good point about Criterion should have done a better job in final assembly. If it was their fault. This scope was manufactured in 1979 and had previous owners. There is no telling what kind of molesting of this system could have taken place. That retaining ring could have been off before. The scope was in great condition, but you never know for sure what was done to it.

I disagree with one thing that many people have said about the Dynamax. They say it is not worth anyones time, effort, or money to fool with. I picked up my 1976 and 1979 Dynamax scopes for "chicken feed", or as some might call it "Chump change", on A-Mart. I will never sell either one of these scopes for any reason. The 76 was fantastic right out of the case and I learned something that ended up bringing me joy about the 1979 model. Imagine the astonishment I felt after fixing that scope and not really confident that I would make any difference in it's performance. This is part of the fun of the hobby.

Mark Swanson

#9 highfnum

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Posted 28 July 2010 - 08:47 AM

i believe the early models 72-74 were pretty bad
they tried to improve and did to some extent but just
like people first impressions last long
once you get a bad rep its hard to shake
it cost them the biz
the corrector plate was a hard thing to make


im not selling mine either it was 78-79 model

#10 Jeff55

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Posted 16 August 2010 - 12:52 PM

It's really too bad that the quality of these scopes was so irregular...for anyone growing up in NYC in the late 1950's and seeing the Criterion displays of their beautifully crafted Newtonian scopes at the Hayden Planetarium...to this day I was never so dazzled by a piece of astronomy gear as I was then.

#11 highfnum

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Posted 16 August 2010 - 12:58 PM

got same memories they had a real large one on display
it was grey

there never was an issue with their dynascopes
only thier SCT dynamax

#12 skywatcher88

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Posted 05 September 2010 - 11:24 PM

I Have used one since 1977 (Bought new and a year later bought the Golden Tripod)and all components still work and I still get great views with it.
Clear Skies!

#13 Mitrovarr

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Posted 28 November 2010 - 12:50 AM

I have one of these scopes. Things to note:

- The optics apparently vary significantly. Some examples are apparently good. However, many owners report seeing examples that are very, very bad. So you are definitely playing the odds on this, if you pick one up. Mine is mediocre and shows evidence of severe overcorrection or undercorrection (images are totally different on each side of focus), and I don't think that could be caused by incorrect assembly or easily fixed. I really wouldn't get one unless it's extremely cheap and you can check out the optics thoroughly beforehand.

- If you have any extra accessories for your Dynamax (photo adapters or anything) and they have one of those rings that attaches them to the back of the telescope, you can use that to make a 2" diagonal for it. Get a 2" diagonal for a normal SCT and switch the ring out that attaches it to the telescope. This works great (or at least it did in my case) and is highly recommended. That's the first upgrade I would do for any 8" SCT, actually (the 2-inch diagonal, I mean.)

- While the tube durability is generally considered sufficient, don't mess with it. The previous owner of my scope drilled it to installed a counterweight system, and that didn't work out too well.

- The golden pyramid tripod, the fork, and the tracking are all pretty nice. I mean, they're not going to compare to a good high-end SCT, but they seem to compare favorably to the some of the low-end ones I've seen (at least, the ones contemporary with it.) You don't get dual-axis drives, but they seem a *lot* less prone to be shaken around by the wind.

#14 jaliteuk

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Posted 30 November 2012 - 04:19 AM

I have just purchased one of the 8" SCT scopes, which has had very little use, the no: 4643. The drive upon inspection has 2 motors driving at the same time, and i wondered if this was because here in England we use 230volts ? The drive is very accurate and smooth, I am delighted with the optical quality of the scope. The only problem was with the finder as the lens was cloudy, i found an alternative lens and rebuilt same ,now very good. By luck the original handbook came with it and was all in a huge case. I think this was built in 1978 but not sure, has anyone a factory list for manafacture dates ?

#15 Masvingo

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Posted 30 November 2012 - 08:41 AM

Hi there.

Glad to hear you are enjoying your Dx 8 and that it has good optics.

As far as I am aware all Dx 8s had dual motors, whether American 110v or European 230V. I assume the aim in using two motors, as with the Celestron C8 of the same vintage, was to try and even out any tracking irregularities, although the use of spur gears will still give rise to more variation than the use of a worm gear which Celestron shifted to and which was used by the Meade SCT.

James

#16 orion61

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Posted 30 November 2012 - 01:33 PM

One other thing to note. Any time you buy a used scope you are getting someting that someone didn't want anymore. I had a DX8 that I sold but kept the SN, I saw that same scope sell 3X in the next year so that one scope turned out to be 3 bad scopes.. But I have had 3 that were either accptable or down right good.
Criterion used to keep a Card on every systems performance that went out, if someone complained about a scope it was brought in, tested and the offending optics were replaced
by hand picked sets. That is more than some do today.
I Have a DX6 (6" Dynamax that has fantastic optics)
also to answer the above post about the dynascope RV6, most every F8 newtonian with a good mirror will out perform a SCT.
A 6" scope is a great scope of any type. They cut through bad seeing better than a larger scope. It is a shame that Lawyers got so much money that it hurt the company
I still love the silkyness of the DX build. The Golden tripod was a decade ahead and much better than anything anyone else was putting out back then.
Another fact is the Later B&L scopes were by far the BEST not the worst they put out, in 1987 they retooled and updated their scopes the resulting 8001, 6001, and 4000 pro series were as good or better than anything else being built and have received glowing reviews, it was a corp. descision to end the production of them. they made more useing the line as a buisness loss. the company had plenty of resources to continue.

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#17 Masvingo

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Posted 30 November 2012 - 02:07 PM

Hi,

Me again, have just checked my serial number (now I'm home) and if Criterion did them sequentially yours should have been built later, mine is number 4268 and was ordered in March 1980 and finally shipped in January 1981. Never did get a reason for the delay.

James

#18 jaliteuk

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Posted 15 December 2012 - 04:59 AM

Hi Masvingo, Many thanks for your note re the scope number, the one i have must be younger, assuming they run in order.How do you find the quality of the image on say jupiter using a 32mm eyepiece ? I can easily see the bands on a good night.John.

#19 Masvingo

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Posted 16 December 2012 - 04:57 PM

Hi John

Currently my longest focal length eyepiece is a 21mm Televue Plössl which gives good views of Jupiter with the bands readily visible as do my 17mm and 13mm Televue Plössls as well, atmospheric conditions permitting. I rarely seem to get steady conditions here - being at sea level on the coast doesn't help - so going much higher than the 13mm generally doesn't do much for me.

My collimation is very slightly off, 'the 'scope as never been collimated since I got it in 1981. :shocked: I'm not sure about its double star performance but need to get the collimation spot on first before making any judgements.

James

#20 jaliteuk

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Posted 17 December 2012 - 04:13 AM

Hi James,
Many thanks for your comments regarding the definition etc, i live in the north cotswolds, and have fair observing here BUT a very yellow street light outside when viewing due south !!!! A LPU filter helps. I have been an astronomer, albeit amateur, for over 60 years. You said your scope may need collimating, there is an article about that on the net , my scope was collimated when i aquired it.All the best, John.

#21 Masvingo

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Posted 18 December 2012 - 02:12 PM

Hi John

I can't quite match 60 years, probably only 45 years and most of the last few years have been of the armchair variety - which suits the Scottish weather the best. :roflmao:

Yes, if I can get a good night I need to have a go at collimating my D8 once I have digested the various articles on the 'net.

James






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