108 replies to this topic

[apfever]

Best way to date the scope is to check the motor. Criterion used Synchron and Haydon motors. The Synchron have a date printed on the motor edge at the end of the print line. The Haydon motors do not have a date. 

The scopes are typically 3 to 6 months after the motor date if it is an original motor.  Carefully look for signs of replacement as you remove the motor, if you have to remove the motor. Sometimes you can find the date on a Synchron with a flashlight and mirror without removing it. 

[Bob Hayes]

Is that the one on FB in Rochester? Very tempting but a 10 hr round trip for me. DM me if you need optics, I may have a lead.

Yes it is! It's home and I may have bit off more than I wanted. It's ruff and going to need a few things made.

[Bob Hayes]

Bob Hayes,

 

That is a Criterion DeLuxe you have procured  Nice find!

 

The two DeLuxes scopes that I'm the temporary custodian of have the best serialization of any telescope (my opinion).   The 6.00" S/N 658069. This is a 6.00" built 1958 S/N 069.  The 8.00" is  S/N 861379   This is an 8.00" built in 1961  S/N 379.  The serial numbers are stamped on the OTA and the mount.

 

Thanks

Bill

Bill,
What do you make of the serial # 1699? It's on both the tube and mount tags.

Thanks

Edited by Bob Hayes, 26 October 2024 - 03:32 PM.

[Bob Hayes]

Good news is, this can buff up like a Jewell.

 

Pete

Pete,

There's no buffing this thing. I had to split collars to disassemble the shafts. I'll be making new collars and a dec shaft.

Someone had their hands into the motor box also. There's a small transformer in there, though the stock 120v motor is there!

[apfever]

Don't use the shaft locks. They cut a raised lip groove into the shafts. The raised lip won't pass out the bushings in the housings which entraps the shafts in the housing. Comment here if you run into this.

[Bob Hayes]

Can anyone tell me the RPM of the stock motor? Thanks !

[azure1961p]

 TEST the mirror. I have tested around 12 of them and they all have been spheres. You will get an image that comes to focus and it will not be a fuzzy mess. So it will easily fool most.  Just when you crank up the power, you will never see the detail that a correctly figured 8" f/8 will produce. The owners swore up and down they had great optics and it gave super sharp images but a simple  30 second Foucault test told a different story.

 

                - Dave 

 

So the sphere is good? Or would a parabola been better?

 

Pete

[YourNotSirius]

Can anyone tell me the RPM of the stock motor? Thanks !

My old man says they should be 1 rpm. Edmunds used a 1/15th rpm on theirs, he thinks. We have one laying around here someplace. I will have him see if he can put his eyes on it.

 

A parabolic mirror will always out perform a spherical mirror when it is below F/10. At F/10 the difference is virtually nil. That's why Edmund made the 4-1/4" scopes at f/10 and the larger f/8 mirrors were f/8. Criterion was supposed to have made the 8" f/8 with a parabolic figure. Maybe they lied. LOL

 

Q

Edited by YourNotSirius, 12 November 2024 - 03:16 PM.

[apfever]

I'll confirm that.

Criterion is 1/10 rpm.

Edmund is 1/15 rpm.

 

Criterion used both Hayden and Synchron motors. I checked both types, they are all 1/10 rpm.  The Synchron are labeled as 6rph (6 rounds per hour) which is the same rate as 1/10 rpm.

 

The F10 focal ratio comments aren't quite right. The diameter of the primary affects the situation. The larger the mirror the longer the focal ratio needs to be to consider a spherical mirror. This is analogous to a refractor and chromatic aberrations. A small refractor (60mm or so) can be apo like F15, but larger lens' will need a longer focal ratio to achieve the same limited dispersion.

Even my statement could be picked apart with more detail. Vlad could have a heyday with all this. On the practical side, the mirror diameter needs to be considered.

 

Edit:  Bob H., also take note that Criterion used a lot of archaic metric Japan JIS threaded bolts. There are a lot of these in the motor box both outside and inside. Don't loose those bolts or you'll be rethreading or cross threading. The finder scope adjusting screws are also JIS M4X 0.75, while the modern threads for 4mm screws are M4X0.7. That very small difference between .75 and .7 pitch is enough to keep most applications from interchanging. 

Edited by apfever, 12 November 2024 - 06:54 PM.

[YourNotSirius]

I'll confirm that.

Criterion is 1/10 rpm.

Edmund is 1/15 rpm.

 

Criterion used both Hayden and Synchron motors. I checked both types, they are all 1/10 rpm.  The Synchron are labeled as 6rph (6 rounds per hour) which is the same rate as 1/10 rpm.

 

The F10 focal ratio comments aren't quite right. The diameter of the primary affects the situation. The larger the mirror the longer the focal ratio needs to be to consider a spherical mirror. This is analogous to a refractor and chromatic aberrations. A small refractor (60mm or so) can be apo like F15, but larger lens' will need a longer focal ratio to achieve the same limited dispersion.

Even my statement could be picked apart with more detail. Vlad could have a heyday with all this. On the practical side, the mirror diameter needs to be considered.

 

Edit:  Bob H., also take note that Criterion used a lot of archaic metric Japan JIS threaded bolts. There are a lot of these in the motor box both outside and inside. Don't loose those bolts or you'll be rethreading or cross threading. The finder scope adjusting screws are also JIS M4X 0.75, while the modern threads for 4mm screws are M4X0.7. That very small difference between .75 and .7 pitch is enough to keep most applications from interchanging. 

OOOPSIE! I heard my old man incorrectly. He said 1/10th RPM, too. I only heard the one part. Sorry!

He's now laughing at me because he's the one we say needs hearing aids. ($%$%&$%!!!)

 

At this small size I the difference between a parabola and a sphere is enough to be noticeable. However, with an smaller scope that should not be the case. Pops says his old Edmund 4-1/4s were planet killers and did quite well on everything else as well.

 

Those old JIS threads are a bit of a both. I don't think we have encountered them except on Japanese scopes. All of the RV-6s that we have use SAE threads or, so it would seem. Regardless, I believe we actually have taps and dies for the older JIS threads. I'll have to ask the old man. They aren't easy to acquire as far as I know but, I'm pretty sure that he has, or had, some around at one point in time. 

 

Q

[deSitter]

I'll confirm that.

Criterion is 1/10 rpm.

Edmund is 1/15 rpm.

 

Criterion used both Hayden and Synchron motors. I checked both types, they are all 1/10 rpm.  The Synchron are labeled as 6rph (6 rounds per hour) which is the same rate as 1/10 rpm.

 

The F10 focal ratio comments aren't quite right. The diameter of the primary affects the situation. The larger the mirror the longer the focal ratio needs to be to consider a spherical mirror. This is analogous to a refractor and chromatic aberrations. A small refractor (60mm or so) can be apo like F15, but larger lens' will need a longer focal ratio to achieve the same limited dispersion.

Even my statement could be picked apart with more detail. Vlad could have a heyday with all this. On the practical side, the mirror diameter needs to be considered.

 

Edit:  Bob H., also take note that Criterion used a lot of archaic metric Japan JIS threaded bolts. There are a lot of these in the motor box both outside and inside. Don't loose those bolts or you'll be rethreading or cross threading. The finder scope adjusting screws are also JIS M4X 0.75, while the modern threads for 4mm screws are M4X0.7. That very small difference between .75 and .7 pitch is enough to keep most applications from interchanging. 

At 6", f/12 for a high-performing sphere. f/10 for 1/4th wave. At f/12 you'd probably have a hard time using a Foucault zonal test.

 

-drl

[KI5CAW]

I own a Royce 8" f/8, an honest Planet Killer. No doubt about its figure! But, the seeing limits what it can do. Its true quality only shines during brief moments of the finest seeing, when fine details of Jupiter's belts suddenly pop into view...for a second or two. So it's easy to see how a spherical 8" f/8 could be "good enough", most of the time.

[DAVIDG]

My old man says they should be 1 rpm. Edmunds used a 1/15th rpm on theirs, he thinks. We have one laying around here someplace. I will have him see if he can put his eyes on it.

 

A parabolic mirror will always out perform a spherical mirror when it is below F/10. At F/10 the difference is virtually nil. That's why Edmund made the 4-1/4" scopes at f/10 and the larger f/8 mirrors were f/8. Criterion was supposed to have made the 8" f/8 with a parabolic figure. Maybe they lied. LOL

 

Q

 The f/10 focal ratio only applies to 4" mirror and smaller, A 6" mirror if left a sphere would have to around f9 and 8" around F/15 to be just at diffraction limited 

  So for a Criterion with  an 8" mirror and f/7  would be very much over corrected if left spherical and would not show the detail that a parabolic mirror would  I have tested a number of 8" Criterion mirrors that were spherical so again I say test the mirror. 

Just because the image looks "good" doesn't mean the mirror is  not spherical. I have seen amateur using telescope with 1/2 wave optics for decades and claim they have great optics. 

   As for the motor it most likely is 1/10 rpm. Count the number of the teeth on main drive gear  and any other gears and   divide that number by 1440. For example if the tooth count is 144/1440  then  the motor  speed  needed is 1/10 rpm. Criterion typically used 1/10 rpm motor to directly drive a 144 tooth gear which results in 1 revolution per day ie solar rate.

 

                    - Dave 

[KI5CAW]

Wouldn't a star test show if the mirror is spherical?

[YourNotSirius]

Wouldn't a star test show if the mirror is spherical?

I believe that is what some have used in the past. We don't have any testing gear so I'm fish out of water on this subject.

 

Q

[deSitter]

Wouldn't a star test show if the mirror is spherical?

Yes. A 6" f/8 sphere would have a highly asymmetrical in/out Airy pattern, and the first 2 rings would be very prominent. You could not achieve a satisfying focus.

 

As the focal ratio increases, the Airy pattern will approach that of a paraboloid ever more closely.

 

-drl

Edited by deSitter, 14 November 2024 - 05:21 PM.

[DAVIDG]

Wouldn't a star test show if the mirror is spherical?

 Yes but in my 40 years of making optics and testing hundreds of them,  unfortunately I  have seen  first hand that many don't know how to do the test correctly and fool themselves  they have great optics. My own RV-6 that I purchased new in 1976 came with a mirror was very much undercorrected with turned edge. I refigured it. 

   To do  the star test correctly you need to use an eyepiece that a has a focal length that is equal to close to the F-ratio of the telescope. So for  an F/8 telescope you  use an 8mm eyepiece or one close to it. 

   Next you need to focus on a medium  bright star  like a 2 mag one and then de-focus very slightly  inward  as in around  1/16 of turn focuser and observe the size of defocused image and the size of the shadow of the secondary in the center of the defocused image.   Next you go back to focus and defocus outward by exactly the same amount you defocused inward. Again your only defocusing a very  slight amount and observing the size of shadow of the secondary.

    If you see that the size of the shadow is larger on the inside then the outside, or there no shadow at all on the outside the optics are undercorrected. 

   The opposite is true, if the optics are over corrected ie you see a larger shadow on the outside then the inside of focus or no shadow at all on the inside.

   Again it is  very critical to use the correct magnification and also defocus only very slightly and by the exact same amount on each side of focus. If not it is very easy to make the defocused image look very similar by defocusing by different amounts or by defocusing too much and then coming to the wrong conclusion you  have great optics when in fact they poorly corrected.

    Using the defocused image on a star and comparing the views on each side of focus is FAR more sensitive that looking at a star that is at focus. See diffraction rings at focus is not an direct indication of well figured optics. Having spherical aberration will  actually make the diffraction rings easier to see.

   

   

                    - Dave 

Edited by DAVIDG, 15 November 2024 - 08:52 AM.

[deSitter]

 Yes but in my 40 years of making optics and testing hundreds of them,  unfortunately I  have seen  first hand that many don't know how to do the test correctly and fool themselves  they have great optics. My own RV-6 that I purchased new in 1976 came with a mirror was very much undercorrected with turned edge. I refigured it. 

   To do  the star test correctly you need to use an eyepiece that a has a focal length that is equal to close to the F-ratio of the telescope. So for  an F/8 telescope you  use an 8mm eyepiece or one close to it. 

   Next you need to focus on a medium  bright star  like a 2 mag one and then de-focus very slightly  inward  as in around  1/16 of turn focuser and observe the size of defocused image and the size of the shadow of the secondary in the center of the defocused image.   Next you go back to focus and defocus outward by exactly the same amount you defocused inward. Again your only defocusing a very  slight amount and observing the size of shadow of the secondary.

    If you see that the size of the shadow is larger on the inside then the outside, or there no shadow at all on the outside the optics are undercorrected. 

   The opposite is true, if the optics are over corrected ie you see a larger shadow on the outside then the inside of focus or no shadow at all on the inside.

   Again it is  very critical to use the correct magnification and also defocus only very slightly and by the exact same amount on each side of focus. If not it is very easy to make the defocused image look very similar by defocusing by different amounts or by defocusing too much and then coming to the wrong conclusion you  have great optics when in fact they poorly corrected.

    Using the defocused image on a star and comparing the views on each side of focus is FAR more sensitive that looking at a star that is at focus. See diffraction rings at focus is not an direct indication of well figured optics. Having spherical aberration will  actually make the diffraction easier to see.

   

   

                    - Dave 

STAR TESTING.jpg

When it gets really bad, you have just indistinct mush on one side, and a perfect target pattern on the other, really like an archery target. That is very bad SA, but the very sharp rings on one side could make you think it was OK.

 

I remember a Criterion RV-6 with a great mirror - same in/out. Maybe it was a Coulter mirror. That scope had some issues when I got it. One of the spider vanes was suspiciously bent. The mirror was good enough to closely follow the occultation of a bright star by Mars in 1976 - when it was only 7" diameter. Amazing view of the tiny 7" planet encroaching on a 2nd magnitude star.

 

-drl

Edited by deSitter, 14 November 2024 - 09:38 PM.

[mstatti]

Hello Everyone,

 

As you might have known, Bob Hayes decided to give away his 8" Dynascope, and I am the one who took it off of him, so I will be continuing to restore this telescope.

 

He didn't mention this here, but he was able to find a new focuser and finderscope, and he got a new counterweight shaft made, so I won't have to worry about the old rusted one!

 

Below is a picture of all of the parts except for the tube and the pier, if there is anything missing, let me know. I think the first step I should take is to de-grease everything, remove any rust, and add new grease. Any suggestions for a de-greaser and new grease to replace it with? I plan on using evaporust for the small parts, but for the giant pier, I might need to go at it with a wire brush. I heard getting it sandblasted is another good idea but I don't know how much it will cost to get that done.

 

 

Thanks,

Matteo

Edited by mstatti, 19 November 2024 - 01:56 PM.

[jgraham]

I have been using Mobil 1 synthetic grease for several years now. Works great and is very stable.

[mstatti]

I'm looking at the broken motor I got from Bob, and it says 1rpm. Do you think this is the right rpm, or could it have been a previous owner's doing and I should just go for a 1/10rpm motor?

 

I found a listing for a 1/10rpm motor, but it is an old listing so it might not go anywhere, should I try to get it?

 

(Sorry for the sideways pictures, Cloudynights seems to enjoy rotating them no matter what I do)

 

Thanks,

Matteo

[DAVIDG]

I'm looking at the broken motor I got from Bob, and it says 1rpm. Do you think this is the right rpm, or could it have been a previous owner's doing and I should just go for a 1/10rpm motor?

 

I found a listing for a 1/10rpm motor, but it is an old listing so it might not go anywhere, should I try to get it?

 

 

(Sorry for the sideways pictures, Cloudynights seems to enjoy rotating them no matter what I do)

 

Thanks,

Matteo

  How many teeth are on the main gear ?  Count the number of teeth on that gear and divided it by 1440. If the number of teeth is 144/1440 then that is 1/10 so that is the speed of the motor. This is what many of the Criterion scopes used 

   Some manufactures would use a 1 rpm that had 10 tooth gear on it. That drove a 144 tooth gear on the worm gear and that drove a the main gear that had 100 teeth and that ratios resulted in 1 revolution in 1440 minutes. So by doing some counting and little a math will give you the answer of what speed motor you need. One other thing you need to pay attention to is the which way the motor turns  That direction will depend if the motor is directly driving the main gear or if there is additional gears. 

 

                  - Dave 

Edited by DAVIDG, 21 November 2024 - 06:38 PM.

[deSitter]

Hello Everyone,

 

As you might have known, Bob Hayes decided to give away his 8" Dynascope, and I am the one who took it off of him, so I will be continuing to restore this telescope.

 

He didn't mention this here, but he was able to find a new focuser and finderscope, and he got a new counterweight shaft made, so I won't have to worry about the old rusted one!

 

Below is a picture of all of the parts except for the tube and the pier, if there is anything missing, let me know. I think the first step I should take is to de-grease everything, remove any rust, and add new grease. Any suggestions for a de-greaser and new grease to replace it with? I plan on using evaporust for the small parts, but for the giant pier, I might need to go at it with a wire brush. I heard getting it sandblasted is another good idea but I don't know how much it will cost to get that done.

 

 

 

Thanks,

Matteo

Those huge spoked setting circles are the absolute coolest thing ever seen on a golden-age scope.

 

-drl

[apfever]

I can not enlarge the previous two images, access denied.  Pictures of the clock drive set up would help. It might be substantially different than the RV series drives. My smaller Dynascopes have the same drive as the RV series. 

 

Those huge spoked setting circles are the absolute coolest thing ever seen on a golden-age scope.

 

-drl

You have mentioned this on a few post. You really like spoked circles eh? I'll pm some pictures but not tonight, it's a barn trip for some of them. 

[deSitter]

I can not enlarge the previous two images, access denied.  Pictures of the clock drive set up would help. It might be substantially different than the RV series drives. My smaller Dynascopes have the same drive as the RV series. 

 

You have mentioned this on a few post. You really like spoked circles eh? I'll pm some pictures but not tonight, it's a barn trip for some of them. 

They should be illuminated, as in an observatory

 

-drl