1143 replies to this topic

[flyboyu777]

I would like to see the details of this eyepiece, most importantly how much - or likely little - spherical aberration of the exit pupil it has. My favorite eyepieces have always been Orthos, because they have almost NO SAEP. You know what has literally zero SAEP? A window. These great eyepieces are so prized because they require no effort to capture the exit pupil. It's like looking out a window.

 

-drl

It's not the specs, it's how it actually works on the back end of your telescope.  I'm never disappointed with the Edmund 28 RKE.  It's a fun eyepiece with crazy eye relief. 

[DozerCSX]

Greetings! 

I have a wonderful, ancient Criterion Dynamax 6 SCT which I rescued from a local dump!

I am missing a crazy little part and was wondering if anyone had advice or guidance on how to find this piece:

- as you face the front of the SCT, there are three tiny stainless screws which hold the secondary apparatus on to the corrector plate. ONE OF THOSE SCREWS IS MISSING! I only have two.

 

Any insights on where to find one of these beauties would be much appreciated!

 

 

Attached Thumbnails

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Edited by DozerCSX, 13 October 2024 - 10:23 PM.

[Terra Nova]

If you are fortunate enough to have an old school, real hardware store that carries an extensive collection of fasteners, you might remove one of the other screws and take it there and see if you can match it. Same if you have a Granger not far away. At the very least you will be able to get the thread and pitch and be able to order one online.

[deSitter]

If you are fortunate enough to have an old school, real hardware store that carries an extensive collection of fasteners, you might remove one of the other screws and take it there and see if you can match it. Same if you have a Granger not far away. At the very least you will be able to get the thread and pitch and be able to order one online.

It's likely some small standard US thread, probably #4. I would just buy a #1 through #6 1 in. long bolt and corresponding nut and try them until it fits. Then cinch the nut down before removing the other screw. Don't know if Criterion used metric fasteners.

 

-drl

Edited by deSitter, 14 October 2024 - 08:50 AM.

[norvegicus]

I would be scared to take out a screw and would take the scope to the store to fit, add a screw, then take out an original to get the length

[jkmccarthy]

This post and the one immediately after it:

 

https://www.cloudyni...help/?p=9036436

 

suggest that the Criterion 6000's three collimation pull-screws surround a central ball bearing that acts as the pivot point between the disk attached to the back of the second mirror and the disk attached to the center of the corrector plate.  Not mentioned is whether the ball bearing is bonded to one disk or the other, or simply held captive between the two disk by the three collimation pull-screws.

 

So like Sean, I'd be very hesitant to remove a second collimation screw -- leaving only one screw installed.  The suggestions above recommending "trial and error" using different thread sizes seem like the best advice.

 

I was unsuccessful finding the thread size on the web, but I did find (see page 2 of the linked PDF) that replacement Bob's Knobs are available here:  http://www.bobsknobs...oldover2211.pdf    If you'd consider "upgrading" to Bob's Knobs after evaluating whether or not the optical system of your Criterion 6000 are very good [*1] (as opposed to 'mediocre at best' for example), maybe an email to Bob's Knobs to inquire about the thread size and length would provide you with this information ?

 

(EDIT:   Maybe a mistake on my part to assume the Dynamax 6 is similar to the Criterion B&L 6000 as regards the secondary mirror's collimation screws??)

 

Good Luck,

 

       -- Jim

 

[*1]  As of 8 years ago at least, CN Classic Telescopes forum participator TerryWood was using his Criterion Dynamax 6 to do some impressive planetary imagery (see:  https://www.cloudyni...oday/?p=8863677 )

Edited by jkmccarthy, 14 October 2024 - 11:59 AM.

[holtter]

UNITRON 114 TANGENT ARM SPRING-PLUNGER THING: does anyone know where I can find a replacement? I picked up a beautiful 114 (going back to my roots, perforce, since my Meade LX 200 hand controller died this summer after 30+ years' loyal service) at a flea market over the weekend. It's in great condition, missing a few odds and ends I won't have trouble making or finding, but what's got me stumped is that TASP thing (see attached image). The plunger on the altitude tangent arm is stuck fully retracted into its housing. I've soaked it in WD40 and acetone, tried pulling on the barely visible end of the plunger with pliers, all to no avail. I suppose I could tap a small hole in the exposed end and see if I could pull it out, but I'm wondering if anyone knows a source for a replacement. It's a lovely little scope, and the mount is otherwise in perfect shape. Any help for this new member greatly appreciated.  Thanks!

Edited by holtter, 16 October 2024 - 10:05 AM.

[deSitter]

UNITRON 114 TANGENT ARM SPRING-PLUNGER THING: does anyone know where I can find a replacement? I picked up a beautiful 114 (going back to my roots, perforce, since my Meade LX 200 hand controller died this summer after 30+ years' loyal service) at a flea market over the weekend. It's in great condition, missing a few odds and ends I won't have trouble making or finding, but what's got me stumped is that TASP thing (see attached image). The plunger on the altitude tangent arm is stuck fully retracted into its housing. I've soaked it in WD40 and acetone, tried pulling on the barely visible end of the plunger with pliers, all to no avail. I suppose I could tap a small hole in the exposed end and see if I could pull it out, but I'm wondering if anyone knows a source for a replacement. It's a lovely little scope, and the mount is otherwise in perfect shape. Any help for this new member greatly appreciated.  Thanks!

Unitron 114 mount.jpg

That device  can likely be unscrewed from the tang so you can access the innards. The ones on classic mounts I've seen are just a simple compression spring.

 

-drl

[holtter]

Thanks so much deSitter! I've unscrewed the device from the tang, as you described. The problem is that the part that is supposed to slide outward, and keep tension on the tangent arm when you back off the slow motion screw is stuck so deep inside the barrel that I can't get a grip on it. A brief application of WD40 and a longer bath in acetone haven't budged it. I'm guessing the spring inside has rusted, or broken, or something. The azimuth device was a little sticky when I took it off, but a shot of WD40 freed it up without difficulty. The spring inside that unit is a little rusty, but otherwise fine.  The only thing I can imagine doing next (after a night's soak in WD40--for the device, not for me), is drill into the business end of the thing, see if I can get a screw into it, and use that as a handle to pull it apart. But I'm not optimistic. So my next question is: how do I track down a replacement?

 

Thanks again! As I said, I'm new to this group, and am very impressed at how helpful everyone is!

 

Hope the skies are clear tonight wherever you are!

[deSitter]

Thanks so much deSitter! I've unscrewed the device from the tang, as you described. The problem is that the part that is supposed to slide outward, and keep tension on the tangent arm when you back off the slow motion screw is stuck so deep inside the barrel that I can't get a grip on it. A brief application of WD40 and a longer bath in acetone haven't budged it. I'm guessing the spring inside has rusted, or broken, or something. The azimuth device was a little sticky when I took it off, but a shot of WD40 freed it up without difficulty. The spring inside that unit is a little rusty, but otherwise fine.  The only thing I can imagine doing next (after a night's soak in WD40--for the device, not for me), is drill into the business end of the thing, see if I can get a screw into it, and use that as a handle to pull it apart. But I'm not optimistic. So my next question is: how do I track down a replacement?

 

Thanks again! As I said, I'm new to this group, and am very impressed at how helpful everyone is!

 

Hope the skies are clear tonight wherever you are!

Welcome to CN! If all else failed, I would drill and tap a hole in the end of the inner plunger, put a screw in it and cinch it down with a nut, then pull on the screw. It will also give purchase so you can work it back and forth trying to free it. Might want to soak it in Naval Jelly.

 

-drl

[Kasmos]

Thanks so much deSitter! I've unscrewed the device from the tang, as you described. The problem is that the part that is supposed to slide outward, and keep tension on the tangent arm when you back off the slow motion screw is stuck so deep inside the barrel that I can't get a grip on it. A brief application of WD40 and a longer bath in acetone haven't budged it. I'm guessing the spring inside has rusted, or broken, or something. The azimuth device was a little sticky when I took it off, but a shot of WD40 freed it up without difficulty. The spring inside that unit is a little rusty, but otherwise fine.  The only thing I can imagine doing next (after a night's soak in WD40--for the device, not for me), is drill into the business end of the thing, see if I can get a screw into it, and use that as a handle to pull it apart. But I'm not optimistic. So my next question is: how do I track down a replacement?

 

Thanks again! As I said, I'm new to this group, and am very impressed at how helpful everyone is!

 

Hope the skies are clear tonight wherever you are!

Those springs have a lot of pressure so maybe you can press it in further to free it up and keep at it until it pops out. Or maybe drill a tiny hole in it's top/head to get more solvent inside it. If it doesn't bundge then slip a firm wire hook thru the hole to pull on it.

[holtter]

Thanks Kasmos! O hadn't thought about getting solvent into the the thing. Sounds promising. I'll let you know.

[k5apl]

The mount I had with the same problem with a sticky TASP, finally came apart.  The spring was incredibly strong- in fact I thought I was never going to get it back together again.  Good luck getting it apart then getting it back together again. 

Wes

Edited by k5apl, 19 October 2024 - 05:26 PM.

[Kasmos]

Yeah, once it's free it could go flying, so protect your eyes and be very careful.

[Garyth64]

I had the same problem with two of my Unitron Alt-Az mounts.  That plunger is tough.

 

I unscrewed the plunger assembly from the mount.  Yep, be careful.  Inside there are two springs.  Both are very strong.  I took the inner one out when I put it back together.

Going back together is the tricky part.  Before I re-installed the plunger, I unscrewed the adjusting bolt. I didn't want to break it.

Then screwed in the plunger, which was difficult, and then screwed the bolt back in.

 

IMO, the adjustment works just as well with only one spring instead of two.

[deSitter]

I had the same problem with two of my Unitron Alt-Az mounts.  That plunger is tough.

 

I unscrewed the plunger assembly from the mount.  Yep, be careful.  Inside there are two springs.  Both are very strong.  I took the inner one out when I put it back together.

Going back together is the tricky part.  Before I re-installed the plunger, I unscrewed the adjusting bolt. I didn't want to break it.

Then screwed in the plunger, which was difficult, and then screwed the bolt back in.

 

IMO, the adjustment works just as well with only one spring instead of two.

Something as strong as suggested would be a serious risk to the aluminum casting!

 

-drl

[Kasmos]

I had the same problem with two of my Unitron Alt-Az mounts.  That plunger is tough.

 

I unscrewed the plunger assembly from the mount.  Yep, be careful.  Inside there are two springs.  Both are very strong.  I took the inner one out when I put it back together.

Going back together is the tricky part.  Before I re-installed the plunger, I unscrewed the adjusting bolt. I didn't want to break it.

Then screwed in the plunger, which was difficult, and then screwed the bolt back in.

 

IMO, the adjustment works just as well with only one spring instead of two.

Maybe it depends on the year of the mount, but there's only been one spring inside the one I remember taking apart to repair and it was extremely strong. (Same for the Soligor mount) It was too strong for my repair (won't go into why) so I replaced it with a weaker one. 

[flyboyu777]

Greetings! 

I have a wonderful, ancient Criterion Dynamax 6 SCT which I rescued from a local dump!

I am missing a crazy little part and was wondering if anyone had advice or guidance on how to find this piece:

- as you face the front of the SCT, there are three tiny stainless screws which hold the secondary apparatus on to the corrector plate. ONE OF THOSE SCREWS IS MISSING! I only have two.

 

Any insights on where to find one of these beauties would be much appreciated!

Did you check with Bob of Bob's Knobs?  I'm guessing he would know what screws you needed-you could call him or email him.  http://bobsknobs.com/

 

 

I just saw another suggested Bob's Knobs. . . . .  

Edited by flyboyu777, 21 October 2024 - 07:28 AM.

[jragsdale]

I'm doing a restore on a Bushnell Sky Chief Jr, the blue and silver one, and need an original tripod center tray, lens cap, leg attachment bolts and wooden carrying case. Let me know what you have, even if it's just from one of the similar 60/700 cousins from that time-frame like a Mayflower or Shrine Manon.

[jragsdale]

Also looking for a Model 38 DEC motor for a Meade LX3 from the 80s.

[mpsteidle]

I'm looking to retrofit a declination drive onto my Cave-eque 10", so am looking for any bits and bobbles that might reduce what I need to manufacture.  If anyone has an old Tangent arm or worm/gear assembly with a DC motor, that would be spectacular.

[deSitter]

I'm looking to retrofit a declination drive onto my Cave-eque 10", so am looking for any bits and bobbles that might reduce what I need to manufacture.  If anyone has an old Tangent arm or worm/gear assembly with a DC motor, that would be spectacular.

This is a happy sight

 

-drl

[dblstar]

In need of some Unitron hardware items...

 

One is a wing bolt (M4.5x1.0mm) for a draw tube clamp, all metal

....and the second is a tee wing bolt for a RA clamp on the eg mount. It is M10x1.5mm and missing its ears!

 

Thanks for looking! Don

 

[mpsteidle]

I am piecing together a Classic Orange C5 for a friend, but it is currently wearing a tripod plate.  I would like to fork mount it for him.  If anyone has a Fork mount and tripod for an orange-tube C5 then I'd be happy to chat.

[SkipW]

I picked up a Jason 313 refractor at an estate sale last weekend. It's very dusty and missing some parts, but it produced a sharp image when pointed at a power pole a block away, the mount and tripod seemed reasonably steady, and the price was good. This looks like something my 9 YO grand nephew could use and may enjoy if cleaned up and serviced.

 

It's a 60 mm / 910 mm refractor on an equatorial mount (stiff, but otherwise seems OK) and wood tripod, and has a cool flip finder (that works).

 

It is missing its lens cap (I understand a Pringles lid may work for this), .965 diagonal, several eyepieces (it has only a .965", 21 mm Kellner), and the two slow-motion stalks. 

 

I have a couple of spare 1-1/4" eyepieces, and it looks like a .965 to 1-1/4 diagonal and slow-motion stalks are available from ScopeStuff and maybe elsewhere, but for more than the cost of the telescope itself. If that's what it takes, so be it, but if anyone has any of those items lying around - lens cap for 3 5/8" OD dew shield, .965 diagonal or diagonal adapter, or slow-mo stalks (6 mm bore) - please let me know!

 

Once the eclipse is past, I'll probably be asking for tips about cleaning and re-lubricating the mount, and removing the dew shield and possibly the dusty lens for cleaning (better I do this because he may be tempted to try).

As I mentioned in another thread I have located and bought all of the pieces I was looking for except for a suitable lens cap. I could not find a plastic can lid close to the right size to use as a lens cap (even spending a good half hour walking around my local supermarket with a ruler. No dice on the Pringles lid - they are way too small), so I 3D printed one at our library for about $2 worth of filament.