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Dynamax 8 production changes

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#1 Masvingo

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Posted 02 December 2012 - 02:15 PM

Whilst surfing about the 'net I've notice a few changes in the Dynamax over the years prior to the Bausch & Lomb period.

1. As mentioned on the serial number thread there was a change from the bolt on corrector retaining ring to a screw on one when Criterion brough production of the corrector cell in-house - this happened sometime between serial number 4268 (mine) and 4627 (Neil/apfever's).

2. The casting for the fork tine carrying the declination circle also was changed at some time between serial number 4268 and 4627 - my declination circle stands out from the arm as shown below whereas that on Neil's is flush with the arm as can be seen in his picture on this thread - 5th pic down on page 1.

3. The declination slow motion was changed from some other arrangement (shorter arm?) to the tangent arm that reaches to the bottom of the fork tine at (I'm guessing) a fairly early stage in production as most of the pictures I've seen show the long arm. A couple of pictures that show the earlier arrangment are here and here. Both these units are in the earlier dull blue colour scheme.

A few questions: :help:
  • What was the reason for the change in the declination circle fork tine casting?
  • What was the earlier declimation slow-mo arrangment?
  • When did these cahnges occur?
  • Are there any other changes pre B&L?

Thanks for any further information.

James

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#2 Gil V

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Posted 02 December 2012 - 03:18 PM

Here is what I can recall about those changes.

The DX8 originally had this little enclosed box on the right fork arm, with a short, spring loaded tangent arm. Fortunately, that was before my time on the Dynamax line, so I think I might have taken apart only one or two of those.

The longer tangent arm with a screw and block was a much better design.

There were no powder blue mounts with the box-type declination slow motion.

Sometime later, the left arm was changed to accommodate a less expensive setting circle. That was fairly close to the time that the powder blue mounts went to a darker blue color.

#3 Masvingo

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Posted 02 December 2012 - 03:46 PM

Thanks Gil, that's very interesting, it was difficult too work out how the box-type declination slow motion worked from the pictures. I've no idea how good it was to actually use but the tangent arm slow motion I find very smooth.

James

#4 orion61

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Posted 02 December 2012 - 05:25 PM

I have a DX6 Dynamax 6" SN 5174. I was wondering if the DX6 were kept with the 8's serial number sequence?
My Dec is the open top counter sunk one like yours.
The other changes were the 8" went from a retaining ring
held in place by screws to a goofy thread in ring retainer! talk about warping and cross threading!!
The color scheme also had another change from the blue fork base to a wrinkle Black.
I must have seen Uncle Rosd share of good Dynamaxes because I have seen 1 good and 2 very good ones,
Of 2 others 1 was OK while 1 was well, YUCK!
Funny thing was the 2 really good ones were the Black base versions,
Possibly Gill knows if these were produced when Criterion was useing Celestrons thin cloth Corrector fabrication
before they agreed to stop useing that technique?
But beware buying one on the Internet, chances are it's probably been sold and resold 4 or 5 times, each time adding to the "their all junk" mentality, even from those who have never even looked through one!
And as Rod said he shuddered about nearly buying one, Criterion took pretty good care of customers that were unhappy with their optics! They were replaced by hand picked scopes.
I know I'd never trade the DX6 I have for the Meade 2080's built between 1980 and 86.

#5 Masvingo

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Posted 02 December 2012 - 06:10 PM

Hi Larry

Yeah, I can imagine the pain in trying to get a threaded ring of that size into the cell without cross threading - I'm glad mine has the bolt on retaining ring.

Any idea, roughly, of how many Dx6s were made compared to the Dx8. The Dx8, from what I can see, seems to be more common so going by your serial number maybe they did keep with the sequence?

Also good to hear that there are good Dxs out there, it's a shame the production quality seems to have been so variable. I think mine is reasonable, I probably need to touch the collimation up a bit but it's difficult getting clear nights here with good enough seeing. How have you found the cool down time? I've heard they can take quite a while to cool down, longer than Celestrons for instance? I'm toying with putting cooling fans in mine similar to what was done in this thread.

James

#6 orion61

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Posted 02 December 2012 - 06:52 PM

I know there arent that many DX6 compaired to the 8's
Mine is mint and it came with the case paperwork, table top tripod and Dyna Tracker. I know I paid too much $450.00 for it
but I know they were far superior to the 8 optically
(Correctors were not made by Criterion but in Japan
So it is a pretty fair bet the 6 will be pretty good.
One thing tho the correctors were a lot smaller than the cell so most are decentered and cannot be collimated.
A guess would be nearly 8 to 1 production between the 2.
I am still looking for one of the connectors on the leg,
that adjust. perhaps I find one being parted out.
The B&L 6000's were decent too but not as good as the Dynamax untill production of the 6000 Pro the last year of full production.
BTW there are still some NOS parts available from Fred Pauli
He still has 2 NOS 6" B&L's!!
Good questions
Larry

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#7 Masvingo

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Posted 03 December 2012 - 08:54 AM

Interesting, I didn't realise that the Dx6 correctors were bought in from Japan.

Amazing that Fred Pauli still has two NOS ones in stock - I see he has quite a few other bits and pieces as well.

James

#8 Gil V

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Posted 03 December 2012 - 11:07 AM

I can assure you that we polished our own correctors at Criterion. 4", 6", 8".

#9 Andy Taylor

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Posted 03 December 2012 - 11:08 AM

Hi Larry

Yeah, I can imagine the pain in trying to get a threaded ring of that size into the cell without cross threading - I'm glad mine has the bolt on retaining ring.

Any idea, roughly, of how many Dx6s were made compared to the Dx8. The Dx8, from what I can see, seems to be more common so going by your serial number maybe they did keep with the sequence?

Also good to hear that there are good Dxs out there, it's a shame the production quality seems to have been so variable. I think mine is reasonable, I probably need to touch the collimation up a bit but it's difficult getting clear nights here with good enough seeing. How have you found the cool down time? I've heard they can take quite a while to cool down, longer than Celestrons for instance? I'm toying with putting cooling fans in mine similar to what was done in this thread.

James


Yeah, cooling fans goooood... :jump:

#10 orion61

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Posted 03 December 2012 - 12:43 PM

I can assure you that we polished our own correctors at Criterion. 4", 6", 8".

Im sorry Gill, it was the secondarys that were made in Japan, the corrector glass was made for you by Naugatuck Glass Co. My memory gets a bit spotty after 40 years. but was the Schmidt curve pre ground in them or did you do that at Criterion?
Why the optical quality difference between the 6 and DX8?
I have never seen a BAD DX6? had the 8" been as good I have no doubt Criterion would still be in buisness.
I am waiting for newtonians to get back in style, my Criterion RV6 still beats most commercial 8" SCT's for image quality.
ALSO do you still have any Dynamax Motors left? My 6 has a bunch of play..
Cant wait to hear all your details in your article.. and thanks for jogging my memory.

#11 Gil V

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Posted 03 December 2012 - 02:47 PM

Naugatuck was our material vendor, just flat glass pieces arrived from them.

You should be able to take the base cover off and adjust motor backlash. Each motor is held on by two socket cap screws. Easy adjustment.

#12 orion61

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Posted 03 December 2012 - 03:45 PM

Thanks, I will try that again but I may have to open the holes a bit more, I tried that but possibly not enough,
I wish I lived closer to you, I'd have you Autograph my DX6 :bow:

#13 Gil V

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Posted 03 December 2012 - 04:47 PM

Sometimes the motor mount holes didn't line up perfectly. If you loosen up both motors, you can usually find a spot that will work.

Don't spin the scope in RA with both motors loose -except as needed to line up the two motors. It helps to keep the RA brake on when fitting the motors. Screws need to be tight, but not crazy tight.

No signatures here. I just worked there, and I've always has a passion for scopes.

#14 Masvingo

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Posted 03 December 2012 - 05:00 PM

I see Fred Pauli is showing S/C Motor Drives (Syncron) for the 4K/6K/8K on his site.

James

#15 Gil V

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Posted 03 December 2012 - 05:16 PM

That's a good idea. If you plug the scope in and turn on the drive, you can see if both motors are operating.

Use some caution, though My Dx8 has exposed leads with the base cover off.

#16 orion61

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Posted 03 December 2012 - 07:55 PM

I'll give it a try, thanks, the flop is pretty annoying
enough to flip the object out of the field.

#17 Al8236

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Posted 04 December 2012 - 03:55 AM

O.K. I've got to ask. Who is Fred Pauli and what is his site?
I do a search and all I come up with is a therapist. Is it someone in our community or.....?

#18 Masvingo

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Posted 04 December 2012 - 09:00 AM

Hi Al

O.K. I've got to ask. Who is Fred Pauli and what is his site?
I do a search and all I come up with is a therapist. Is it someone in our community or.....?


Used to be Pauli's Wholsale Optics but now Astroptx.

See also this thread.

James

#19 orion61

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Posted 04 December 2012 - 09:28 AM

Gill, I have been looking for more information on the Dynamax 4 SCT were these actually Blue/grey dynamax? or were they the black B&L 4000? I have 2 of those. I really like them for quick peeks. but there are some real bow wows out there. I had one that the corrector was installed backward! BUT thhat could have happened after being sold.
I also had one where the optics were so pinched Christmas lights looked like triangles.. but straightened up fairly well.
The ones I have now are the old style and the newer Aluminum tube style.

#20 Gil V

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Posted 04 December 2012 - 11:19 AM

I will probably take some heat on this, but if my memory is correct, the orientation of a Schmidt corrector does not matter. The edge rays diverge and the center rays converge - regardless of what side faces out.

#21 orion61

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Posted 04 December 2012 - 11:56 AM

It made a difference when i flipped it, BUT it may have been due to rotating the corrector on it.. I didn't know better back then.
Did you Criterion mark the corrector/cell with an alignment mark like Celestrons (it is at the 3:00 position)

#22 Andy Taylor

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Posted 04 December 2012 - 12:15 PM

It made a difference when i flipped it, BUT it may have been due to rotating the corrector on it.. I didn't know better back then.
Did you Criterion mark the corrector/cell with an alignment mark like Celestrons (it is at the 3:00 position)


Mine has an engraved line on the front edge. Not very useful as my DX is now completely disorientated... Bit like me ATM.

As this is my "rat" scope I even took out the corrector and mounted the secondary on a makeshift spider. :lol:

Very interesting...... But STUPID!!!! :tonofbricks:

The corrector does indeed correct... :smirk:

#23 Masvingo

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Posted 04 December 2012 - 02:29 PM

Hi Andy

Very interesting...... But STUPID!!!! :tonofbricks:

The corrector does indeed correct... :smirk:


At least this helps defend against the statements that the Corrector was just a flat sheet of glass in the Dynamaxes!

James

#24 orion61

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Posted 04 December 2012 - 03:10 PM

Hi Andy

Very interesting...... But STUPID!!!! :tonofbricks:

The corrector does indeed correct... :smirk:


At least this helps defend against the statements that the Corrector was just a flat sheet of glass in the Dynamaxes!

James

AMEN....
I have always been a fan of the Max, I thought they were built better than others at the time, had better accys, and have had a couple really good ones, and have now a 6" that is a superb scope for any age,
I think the people that made them not only did a good job
with the assembly but actually with what they had to work with probably put more heart into their work than ANY other SCT makers. Also remember the quality of glass coming in was beond their control. a good batch of optically pure glass made a good scope. I know I have had them and am not ashamed to say it, I cant say that for everybody!

#25 Masvingo

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Posted 04 December 2012 - 03:26 PM

Found this post on the CN ATM forum which suggests that once the plate and primary have been figured together, the plate has to be installed in the same orientation as it was figured.






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