13 replies to this topic

[ericb760]

It involved flipping the rings around 180 degrees and installing four (?) paint stirrer sticks to avoid crushing the tube. I have created the four paint stirrers but I am running in to a problem. The Polaris mount has inserts that must be removed in order to attach the rings 180 degrees from the original placement. Once the inserts are removed, the hole is larger than the hole on the rings. I know I have seen a thread here explaining the process but I can't seem to locate it now. Can someone help me out?

[jupiter122]

It involved flipping the rings around 180 degrees and installing four (?) paint stirrer sticks to avoid crushing the tube. I have created the four paint stirrers but I am running in to a problem. The Polaris mount has inserts that must be removed in order to attach the rings 180 degrees from the original placement. Once the inserts are removed, the hole is larger than the hole on the rings. I know I have seen a thread here explaining the process but I can't seem to locate it now. Can someone help me out?

This one maybe?

 

https://www.cloudyni...k#entry12416356

 

Tim

[ericb760]

This one maybe?

 

https://www.cloudyni...k#entry12416356

 

Tim

Yes, that's the one, or at least one similar to what I was looking for. 

 

Thanks!

[apfever]

That was me and the above link is not the one.  I'll look around but I'm bad a searches. 

 

You need to get a 1/4-20 bolt or knob which will slip through the larger holes in the mount plate and screw into the rings. The bolt length needs to be long enough to grab the rings securely but short enough to not go all the way into the OTA.  Easy enough hardware item or use washers to shim the bolt out.  Just make sure the bolt does not go all the way through the rings and into the OTA.  

 

The inserts are uncommon items so don't lose them. These scopes are vintage, classic, and collectable. They have intrinsic value because they also perform in both the OTA and the praised Polaris mount. The modification is entirely reversible but only if you don't lose the hardware.  

 

I used the paint sticks one day because they were handy and fit the rings perfectly. They are an easy item to get if you can't make a single stick. A single stick would be more convenient and can look awesome using a nice wood with a nice finish.  I would glue the paint stick stack together after everything has been assembled and confirmed. I prefer a hardwood but I still have a scope with the stir stack - that I never glued. 

[apfever]

I am holding an original Celestron clamp knob that worked perfectly. I have a lot of knobs. You will have to find something because the original set up is going to be short a set of clamp knobs. The original clamp knobs are going to be used on the top with the stick. Jasmine informed me one day that guys are knobs. 

The insert removed from the hole is sitting on the saddle next to the a felt pad.  The other insert is shown installed. 

 

Looks are deceiving.  The OTA is held up off the crushing saddle contacts when mounted this way. The dimples in the stick are shallow, just deep enough to let the knobs hold the stick in place when the knobs are loosened to rotate the OTA. And I just got hit with an epiphany for the more advanced. The removed inserts could be installed into the stick! That works for everything, storage, function, aesthetics, and a collector might find it a nice tie in to 'originality'.  Hmmmmm tempting. 

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Edited by apfever, 01 April 2025 - 08:17 AM.

[apfever]

The distance between the dimples in the stick need to match the distance between the mounting holes in the saddle plate. Do not mount the system up and then measure the distance between the holes in the rings where the stick goes. The rings can clamp up out of parallel. Matching the dimple separation to the saddle holes will lock the rings in the position they were designed for. It will look better and work better.  I have found that a badly crushed OTA can still rotate nicely in the mod. It is a smooth working assembly.

 

I made this one from 13 ply cabinet grade plywood and rounded a nice finish on it along with a felt liner. They can be stained or painted for extra 'Wow'. 

 

Keep the clamp knobs slightly tensioned when the OTA is removed from the mount. No more sloppy rings slamming around on your dismounted OTA!  Not only that but both rings will be held in place ready to mount back up. The tube will be balanced where you left it. No more sloppy rings you have to position independently.  The OTA  will look better as a stand alone (pending your stick) with an official appearance instead of loose rings hanging who knows where.  You can stand the OTA on end with no issues...

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Edited by apfever, 01 April 2025 - 08:57 AM.

[deSitter]

The Vixen Custom alt-az head has a similar saddle. I bolted an aluminum bar 1/4" thick across the channel, leaving enough at the ends to attach normal hinged rings. This type of saddle/rings is one of the worst ideas ever!

 

-drl

[apfever]

The C series refractors are held with the same captive ring system. The modification can be used on them as well but the refractor tubes are much more resistant to crushing. The refractors are also less likely to need rotation in use. The modification will help a lot for storage and re mounting. I think it looks good in use and looks a ton better off the mount. I put the mod on my O.T. C80. 

 

While you're at the hardware store, get some other cheap stuff for NO BRAINER mod number 2.  Get a 5/8" nylon washer and metric M16X2 nut, if you trust me then get more than one (see the picture). No need to explain it since the learning curve is almost instantaneous. No tools needed for anything, it's all a flick of the wrist and rock solid. Just check it out, you'll never go back. The mod will work on other threaded rod designs too and it wipes out a lot of the complaints about these.  It looks good on Unitrons.

 

The lock collar on the shaft should go on with the open end against the mount and the threaded end towards the weight. A lot of people get this reversed. The right way supports the shaft a lot better. 

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Edited by apfever, 01 April 2025 - 09:23 AM.

[Kasmos]

After several searches I found a few posts mentioning this technique and one that lead me to Neil's (apfever) original post on it.

 

https://www.cloudyni...ing-mount-easy/

 

The one that lead me there had some additional comments by Neil

 

https://www.cloudyni...unt/?p=13263627

 

So they can be easily found I'm posting these in the How To Thread.

Edited by Kasmos, 01 April 2025 - 08:09 PM.

[jkmccarthy]

The distance between the dimples in the stick need to match the distance between the mounting holes in the saddle plate. Do not mount the system up and then measure the distance between the holes in the rings where the stick goes. The rings can clamp up out of parallel. Matching the dimple separation to the saddle holes will lock the rings in the position they were designed for. It will look better and work better.  I have found that a badly crushed OTA can still rotate nicely in the mod. It is a smooth working assembly.

 

I made this one from 13 ply cabinet grade plywood and rounded a nice finish on it along with a felt liner. They can be stained or painted for extra 'Wow'. 

 

Keep the clamp knobs slightly tensioned when the OTA is removed from the mount. No more sloppy rings slamming around on your dismounted OTA!  Not only that but both rings will be held in place ready to mount back up. The tube will be balanced where you left it. No more sloppy rings you have to position independently.  The OTA  will look better as a stand alone (pending your stick) with an official appearance instead of loose rings hanging who knows where.  You can stand the OTA on end with no issues...

[...]

 

Thanks for this ... the 2nd photo you posted (shown above) very nicely illustrates how your plywood "tube crusher bar" installed across the top of the tube performs the analogous function to Vixen's original scheme, but as stated, in your reimagined concept the plywood tube crusher bar conveniently stays with the OTA and keeps the rings under tension around the tube when all of it is taken off the Polaris saddle.  Ingenious!

 

Just a couple of questions:

1. Does the OTA tube still nestle in the felt tabs of the Polaris saddle's V-block, as happens in Vixen's original scheme when the tube-crusher tension would serve to pull the OTA into the V-block feature of the saddle ?   In other words, with the plywood tube crusher bar on the top and threaded connections between the rings and the saddle ears underneath, when the OTA is pointed at the N.C.P. (alpha Ursae Minoris) and both the R.A. and Decl. axes of the mount are clamped, does the OTA exhibit any teeter-totter rocking tendency to move east-west inside the rings (as conceivably it might in the absence of being well-seated into the saddle's V-block) ?
2. Is the length of the plywood tube crusher bar on top "optimal" as shown in your photo above ?   That is, does the plywood bar's length being roughly twice the spacing between the knob fasteners (below) / tensioners (above) work better than it would if the top+bottom ends of the plywood bar were cut-off just after they emerge out from under the far-left and far-right edges of the tube rings ?   Am I correct in thinking the extra length is to minimize the risk that the ends of the plywood bar --- if located near the knob tensioners on top --- might be more inclined to dent (i.e., dig-into) the tube wall of the OTA ?

Thanks in advance for sharing your experience and thoughts on these two topics !

 

Clear Skies,

 

         -- Jim

[apfever]

1.  The tube is held off the original saddle contact points. I've never noticed the tube moving at all in the rings regardless of position when applying pressure to the stick within easily non damaging pressure.  N.C.P. with ra and dec locks...etc?  Think I've checked that?  I've checked the rings individually before putting the whole thing together and found the rings seat solid to the saddle. I'm sure there are casting variations and someone will find a ring that seats with a 'high' spot.  I would probably tack a rim gasket to the perimeter of the ring flat if I ran into that and it was an issue that I wanted to continue past.

 

2.  A bit of over analysis. "Optimal"?  I originally used a solid stick that was at a convenient length. I cut what looked good on other things. I used a stack of paint stir stick one time and cut off the handle part to make it look better. All my personal preference. Look at it this way, the length of the stick far exceeds the length of the original 4 contacts. It's not a numerically engineered thing, it's a horse sense approach that's worked well for me.  In theory this or the original system has infinite pressure because the contact is on a line and not an area but the stick line is a lot longer than the original. I'm pretty sure any actual engineering on the fix would be well beyond what any manufacturer would do. They obviously blew it on the original design. No checks on flex in the stick. My contact points look nicely distributed on the stick.  I wouldn't want one flush to the rings which would also put the most flex force on the stick. 

 

I totally winged it on my first crude try and it worked great for me, and on all the rest. Beats the pants off the original - for me. 

[ericb760]

I completed the mod with the advice of many in this thread. It seems to work perfectly. Many thanks to all who answered my question.
 

[Bomber Bob]

Looks great!  IMO, these C4.5N old scopes are very fine sleepers.  I wimped-out, and bought hinged rings + dovetail to use mine...

 

Optically, the original Vixen-made mirrors out-performed 2 different samples of the much newer PRC-made versions.  I wasn't a fan of the original POLARIS EQ, but it carried the scope well -- it was stable enough for high-power observing.  And, IME, the C (V) 4.5N stays sharp at 50x per inch -- very good for a Newt.

[Jon Isaacs]

Wimping out was the right thing to do ..

 

Jon