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Jumped on a Cave

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#126 CHASLX200

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Posted 25 October 2018 - 05:40 PM

That V shaped notch sounds promising. If you have any more info on such a setup would appreciate it.

That is something the scope makers should have done 50 years ago.  Also the Latitude adjusters were never done right from the get go.


Edited by CHASLX200, 25 October 2018 - 05:40 PM.

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#127 CHASLX200

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Posted 27 October 2018 - 10:52 AM

Threw the Cave on the bench.  The foucser screws were all loose as a goose and the spider vanes.  I hate Novak 2dnary holders..  So Geo can't cry about this OTA as nothing on it is Cave.  I have all the factory Cave parts that came with another tube. Took a hour to adjust the 2ndary holder.

 

106ngjo.jpg


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#128 starman876

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Posted 27 October 2018 - 11:04 AM

Nice looking OTA.  Looks almost as nice as the one I sold you.



#129 Geo31

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Posted 27 October 2018 - 01:11 PM

Actually, some Caves came with a Novak spider.  My 12.5" did.


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#130 CHASLX200

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Posted 27 October 2018 - 03:08 PM

Actually, some Caves came with a Novak spider.  My 12.5" did.

But the owner told me he bought this scope in 1976 from the first owner. He then redid the whole OTA with all new parts and a refigure in 1988. He gave me the extra Cave OTA and all parts. So now i have a Cave tube with the sticker, mirror cell, spider and holder just sitting around and not sure what to do with it. 

 

Both ends of the tube need to be  cut off and any mirror faster than F/5.3 should work fine.  Maybe a make a F/4 out of it.  I have no plans to reuse the tube and parts so maybe i should just sell them.  Shipping the tube would cost as much as i would get selling the stuff.  So maybe a local sale if someone had a nice sub F/5.3 or faster Cave mirror laying around.\

 

The Novak mirror cell is not easy to adjust. It uses bolts to adjust, so i gotta use a socket wrench.. So not sure who dreamed up that idea. I may re install the Cave mirror cell.

 

Notice the odd color of the Cervit mirror blank.

8zk0uw.jpg


Edited by CHASLX200, 27 October 2018 - 03:12 PM.

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#131 CHASLX200

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Posted 28 October 2018 - 07:52 AM

Always hated adjusting the 2dnary of Newts. Screws are always hard to get to and see. Plus the whole holder wants to spin when adjusting a screw.

2j0f4gh.jpg


Edited by CHASLX200, 28 October 2018 - 07:54 AM.


#132 jcricket

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Posted 28 October 2018 - 09:30 AM

Always hated adjusting the 2dnary of Newts. Screws are always hard to get to and see. Plus the whole holder wants to spin when adjusting a screw.

2j0f4gh.jpg

This is one change I did on my Cave. I bought an astrosytems spider and secondary holder. It is MUCH more user friendly with collimation adjustment. 



#133 tim53

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Posted 28 October 2018 - 09:48 AM

Threw the Cave on the bench.  The foucser screws were all loose as a goose and the spider vanes.  I hate Novak 2dnary holders..  So Geo can't cry about this OTA as nothing on it is Cave.  I have all the factory Cave parts that came with another tube. Took a hour to adjust the 2ndary holder.

 

106ngjo.jpg

I see Cave rotating rings, Cave end rings, Parks fiberglass tube (probably), either a Rukes or Sky Micro focuser, and a Cave finder (the one with the helical focuser that Optical Craftsmen also used).


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#134 starman876

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Posted 28 October 2018 - 10:04 AM

I see Cave rotating rings, Cave end rings, Parks fiberglass tube (probably), either a Rukes or Sky Micro focuser, and a Cave finder (the one with the helical focuser that Optical Craftsmen also used).

I think Tim is trying to tell us somethinggramps.gif



#135 CHASLX200

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Posted 28 October 2018 - 10:43 AM

I see Cave rotating rings, Cave end rings, Parks fiberglass tube (probably), either a Rukes or Sky Micro focuser, and a Cave finder (the one with the helical focuser that Optical Craftsmen also used).

The rings and finder were taken off the other Cave tube i have. Even has extra rods for the rings. The Sky mirco also was reused from the other OTA.  So maybe i need to have a F/3.2 ZERODUR made for the the other tube for kicks.



#136 CHASLX200

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Posted 09 January 2019 - 09:17 PM

Got the mount back from the machine shop after it sat for weeks.

Optics are a killer.

 

Something very odd with the mount as it feels and acts like a loaded spring whenever the OTA is touched. No clue what would cause this. Owned many of these mounts and never seen something like this before.  A object will dance around whenever the tube is touched for like 5 to 8 secs.

 

So if anyone has any clue or had this problem post up.



#137 Jeff B

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Posted 10 January 2019 - 11:20 AM

Got the mount back from the machine shop after it sat for weeks.

Optics are a killer.

 

Something very odd with the mount as it feels and acts like a loaded spring whenever the OTA is touched. No clue what would cause this. Owned many of these mounts and never seen something like this before.  A object will dance around whenever the tube is touched for like 5 to 8 secs.

 

So if anyone has any clue or had this problem post up.

Sounds like some sort of stiction issue there Chas. At least that's been part of my experience.  Which axis rings?

 

Jeff



#138 CHASLX200

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Posted 10 January 2019 - 07:04 PM

Sounds like some sort of stiction issue there Chas. At least that's been part of my experience.  Which axis rings?

 

Jeff

I'm not sure yet. I got this scope back in Oct i think. Used it one nite with a loose polar axis and then the mount went to the machine shop to have a threaded hole to use as a lock down if i wanted to go without the drive.  So it sat there what seemed like forever.   I snugged up the main bolt that locks down the polar axis and the small Allen heads.  Both axis move smooth as silk.  But then i focus there is massive flex like a wound up tuning fork. A image will just dance around the FOV.

 

I grew up with long focus non driven Newts, i always place the object out of the FOV then wait for it to drift into the FOV.  You can tug on the end of the tube and let go and see the OTA just jitter around.  Just drives me nuts to see a object dance around so much.

 

When i get time i will fool around with the mount and try to figure this all out.



#139 tim53

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Posted 11 January 2019 - 11:38 PM

Instead of adding a lock screw to the RA axis, why not simply leave the drive unplugged?

 

A long-focus 10" on the 1 1/2" shaft mount WILL jiggle quite a bit.  Planetary viewing without a drive would be agony.


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#140 dhferguson

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Posted 12 January 2019 - 03:23 AM

Cheers,

 

Which axis (or both) is the jitter occurring in?

 

I have a 10" f/6.6 tube (67 lb in total) mounted on an Astrola mount with 1.5" axis, perhaps just a bit longer and a little heavier than yours? I see about a 3s settling time after moving the tube and that is all, even at x480. Wind will disturb my telescope but it settles just as fast once the gusts stop.

 

Try the following:

--(1) first make sure your telescope is balanced, both in RA and Dec. To do this:

       (i) loosen both axes completely

       (ii) first the Dec axis: position the RA axis so the Dec axis rotates in the vertical

       (iii) tighten the RA axis so it doesn't move

       (iv) rotate the telescope tube in the DEC axis to horizontal. Even with the Dec axis completely unlocked, the telescope tube

            +intermediate-weight eyepiece should balance essentially perfectly. If not, you must add weight on the appropriate

             tube end. Lead fishing weights drilled for a small bolt work nicely, BTW, and can be mounted on the inside end of

             either tube,

       (v) next the RA axis: position the telescope to point along the polar axis, tighten the Dec lock, and completely loosen the

            RA lock. Move the telescope so that the Dec axis is horizontal,

       (vi) you guessed it--the telescope should balance about the RA axis. If not, loosen the counterweight set screw and slide

             the counterweight to balance, then retighten the set screw and retaining locking collar (I am assuming everything

             works and is not gummed up by rust), and

        (vii) I am ignoring the radial balance (rotation along the tube axis). I assume this isn't too far out of balance. If it is, weights

              opposite the "heavy" portion of the tube (usually a counterweight mounted on the outside, and a slider is nice

              to accommodate differing eyepiece weights, see (iv)).

 

(2) if (1) doesn't work, what are the conditions of the bearings? Is the motion utterly smooth (it should be)? Is there "play" in either axis when you attempt to wiggle them? Does either  axis slip longitudinally in its bearings? The answer to the preceding two questions s/b "no." If the motion isn't smooth, you may either need to grease the bearings or replace them. If "wiggle" in any dimension is detected, you have a problem that you'll need to disassemble the shaft and bearings from the housing to diagnose: 'could be bad or rusty bearings, 'could be play between the bearings and the housing(s), 'could be the shaft slipping in the bearings. The first is the most likely,

 

(3) It doesn't appear you have the Cave Dec drive so it can't be the Dec (similar to the RA gear) ring gear clutch.

 

Let us know.

 

Don


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#141 CHASLX200

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Posted 12 January 2019 - 06:30 AM

Instead of adding a lock screw to the RA axis, why not simply leave the drive unplugged?

 

A long-focus 10" on the 1 1/2" shaft mount WILL jiggle quite a bit.  Planetary viewing without a drive would be agony.

I grew up without drives so i am right home without using one. The problem with these mounts are the clutch that sticks when trying to center a object at very high power. Without a drive i can center stuff smooth as silk. Had so many of these mount and never seen flex like this. The scope is worth keeping and i may just have to bit the bullet and spend 5k on a good used mount.

So the mount as it is now centers a object fine and smooth, but once you try to focus the image jitters all over the place.



#142 CHASLX200

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Posted 12 January 2019 - 06:35 AM

Cheers,

 

Which axis (or both) is the jitter occurring in?

 

I have a 10" f/6.6 tube (67 lb in total) mounted on an Astrola mount with 1.5" axis, perhaps just a bit longer and a little heavier than yours? I see about a 3s settling time after moving the tube and that is all, even at x480. Wind will disturb my telescope but it settles just as fast once the gusts stop.

 

Try the following:

--(1) first make sure your telescope is balanced, both in RA and Dec. To do this:

       (i) loosen both axes completely

       (ii) first the Dec axis: position the RA axis so the Dec axis rotates in the vertical

       (iii) tighten the RA axis so it doesn't move

       (iv) rotate the telescope tube in the DEC axis to horizontal. Even with the Dec axis completely unlocked, the telescope tube

            +intermediate-weight eyepiece should balance essentially perfectly. If not, you must add weight on the appropriate

             tube end. Lead fishing weights drilled for a small bolt work nicely, BTW, and can be mounted on the inside end of

             either tube,

       (v) next the RA axis: position the telescope to point along the polar axis, tighten the Dec lock, and completely loosen the

            RA lock. Move the telescope so that the Dec axis is horizontal,

       (vi) you guessed it--the telescope should balance about the RA axis. If not, loosen the counterweight set screw and slide

             the counterweight to balance, then retighten the set screw and retaining locking collar (I am assuming everything

             works and is not gummed up by rust), and

        (vii) I am ignoring the radial balance (rotation along the tube axis). I assume this isn't too far out of balance. If it is, weights

              opposite the "heavy" portion of the tube (usually a counterweight mounted on the outside, and a slider is nice

              to accommodate differing eyepiece weights, see (iv)).

 

(2) if (1) doesn't work, what are the conditions of the bearings? Is the motion utterly smooth (it should be)? Is there "play" in either axis when you attempt to wiggle them? Does either  axis slip longitudinally in its bearings? The answer to the preceding two questions s/b "no." If the motion isn't smooth, you may either need to grease the bearings or replace them. If "wiggle" in any dimension is detected, you have a problem that you'll need to disassemble the shaft and bearings from the housing to diagnose: 'could be bad or rusty bearings, 'could be play between the bearings and the housing(s), 'could be the shaft slipping in the bearings. The first is the most likely,

 

(3) It doesn't appear you have the Cave Dec drive so it can't be the Dec (similar to the RA gear) ring gear clutch.

 

Let us know.

 

Don

Balance is a dream.  Motion is a dream and trying to center a object is a dream at even 500x.  The inside of the mount is clean and looks like new.

 

I have no clue what the problem is. When i grab the saddle i feel flex.  I will tear into things and take pics sometime soon.  I can reinstall the drive at anytime.

 

I had a older Edmund 1.5" shaft mount that was the best mount i ever owned with no drive.  Smooth as silk and worked great with a 8" F/8 Newt.  I know none of these mounts were that great for the 10" and 12.5" scopes, but this is very odd to have this much jitter.

 

Nothing has been changed to upset the balance.  I can unlock both axis and the scope stays put, has tube weighs that you can adjust.  The flex seems to be in the saddle area and tube. When i remove the tube weights there is less flex and weight hanging off the end of the tube. 


Edited by CHASLX200, 12 January 2019 - 07:30 AM.


#143 CHASLX200

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Posted 12 January 2019 - 07:35 PM

Have the scope out tonite and the moon is just insane with this mirror. Mount works perfect to center stuff and stays put. Even with a 3mm Delite and 2x barlow i have no problem to center a object. This mirror is Zambuto all the way.  Just get too much jitters at high powers, so i place the object outside the FOV and by the time it drifts into view it is nice and steady.

 

I am going to buy a much better mount since the optics are so good.


Edited by CHASLX200, 12 January 2019 - 07:35 PM.

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#144 CHASLX200

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Posted 13 January 2019 - 11:52 AM

Got the drive back on and now back to the slop of the clutch sticking. Will give it a shot tonite. I will also have to adjust the clutch, too tight and it is hard to move. Balance is a dream in both axis. I have not changed out anything to upset balance. I am not crazy with the finder mounted below the focuser and it is not a RA finder so kinda hard on the neck.  But views are to kill for.  2e67m1l.jpg


Edited by CHASLX200, 13 January 2019 - 08:14 PM.


#145 dhferguson

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Posted 14 January 2019 - 05:16 PM

Cheers,

 

Based on your prior posts, it doesn't sound like the mount itself is causing your jitter. Perhaps the motion is being produced in the tube rotating rings? Is there play or jiggle when you attempt to wiggle the tube in the rings? I have the Parallax rings but the Cave rings are similar in one respect: both use teflon inserts cut from long teflon rods (think like pencil erasers) for smoothness. Perhaps one or more of these are missing? I'm not sure how the teflon is retained in the Cave rings so I can't help you further. For others' info, the retaining screws on the outer perimeter of the Parallax rings can be remove one at a time to inspect for the presence of the teflon "eraser" plugs.

 

You also mentioned the clutches. It doesn't look like you have the Cave Dec drive, which typically has a play that can be adjusted to yield a relatively small amount of backlash (better than with the RA drive). The RA drive is a different story. The drive gear is a ring gear with an inner lining of teflon. Try backlng off the tension screws (the three Allen head screws located on the face of the round plate mounted on the shaft. This should loosen the drive, then see if you still have "jitter." Next. sometimes, the ring gear/teflon interface can be gooped up with dirt and grease. If so, the drive must be disassembled to clean it. Another possibility: the rough-machined elongated "U" machined stock piece that holds the worm gear may be loose, in which case you can tighten it with and Allen head wrench. Perhaps the worm is loose in the bushings? If so, remove the "U"-shaped mount and eliminate the play by adjusting the brass worm bushings in the stock piece, taking care to eliminate play while not binding the worm.

 

Incidentally, you cannot remove all the backlash from the RA drive because the aluminum stock piece holding the worm gear bends/warps at the two "ears" when the axis is rotated. This backlash does not cause jitter but is annoying at high power. This is a flaw in the Cave drive implementation, and the major reason some of us have gone to Byers drives (now nearly unobtainable, BTW). 

 

I hope one of these works for you, best of luck!

 

Happy observing always,

 

Don



#146 CHASLX200

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Posted 14 January 2019 - 07:20 PM

Cheers,

 

Based on your prior posts, it doesn't sound like the mount itself is causing your jitter. Perhaps the motion is being produced in the tube rotating rings? Is there play or jiggle when you attempt to wiggle the tube in the rings? I have the Parallax rings but the Cave rings are similar in one respect: both use teflon inserts cut from long teflon rods (think like pencil erasers) for smoothness. Perhaps one or more of these are missing? I'm not sure how the teflon is retained in the Cave rings so I can't help you further. For others' info, the retaining screws on the outer perimeter of the Parallax rings can be remove one at a time to inspect for the presence of the teflon "eraser" plugs.

 

You also mentioned the clutches. It doesn't look like you have the Cave Dec drive, which typically has a play that can be adjusted to yield a relatively small amount of backlash (better than with the RA drive). The RA drive is a different story. The drive gear is a ring gear with an inner lining of teflon. Try backlng off the tension screws (the three Allen head screws located on the face of the round plate mounted on the shaft. This should loosen the drive, then see if you still have "jitter." Next. sometimes, the ring gear/teflon interface can be gooped up with dirt and grease. If so, the drive must be disassembled to clean it. Another possibility: the rough-machined elongated "U" machined stock piece that holds the worm gear may be loose, in which case you can tighten it with and Allen head wrench. Perhaps the worm is loose in the bushings? If so, remove the "U"-shaped mount and eliminate the play by adjusting the brass worm bushings in the stock piece, taking care to eliminate play while not binding the worm.

 

Incidentally, you cannot remove all the backlash from the RA drive because the aluminum stock piece holding the worm gear bends/warps at the two "ears" when the axis is rotated. This backlash does not cause jitter but is annoying at high power. This is a flaw in the Cave drive implementation, and the major reason some of us have gone to Byers drives (now nearly unobtainable, BTW). 

 

I hope one of these works for you, best of luck!

 

Happy observing always,

 

Don

The rotating rings glide smooth as butter.  When i remove the OTA and bang on the counter weight shaft it rings so it has to be in that area of the mount.  I had a hole drilled in the polar axis for a lock down bolt as i like using these mounts without a drive as motion is much smoother.

 

At the powers i use with the drive installed you always get that clutch stick when trying to center a object. So once i focus and let the object drift into view i get a great image of Mars at 500x. Just never had a 1.5" mount with the jitters like this one.



#147 dhferguson

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Posted 15 January 2019 - 02:13 AM

Cheers,

 

Hmm,  I hope you removed the RA drive shaft and bearings before drilling that hole in the "polar axis" housing. Otherwise, there are probably metal chips inside the polar axis and they might eventually work their way into the bearings, particularly the lower bearing. You might think about disassembling the polar axis for a cleaning (your local astronomy club may be able to help).

 

Regarding the clutch, you should find with the telescope balanced that only light pressure from the three Allen head screws is needed to engage the drive. The clutch may still stick just a tiny bit if properly cleaned and adjusted but the main source of the backlash is the "ears" on the worm gear mount.

 

Can you isolate the jitter to the RA or Dec axis?

 

Cave used Sealmaster bearings on both axes--very much over-designed--pressed into the casting so it would be odd that the Dec shaft would loosen up in its bearings. Perhaps, somehow, the bearings went bad. I wonder if some sort of horrible mistreatment (like dropping the mount repeatedly) somehow flattened or dimpled some of the bearing surfaces? Unfortunately, if indeed the problem seems to be in the Dec axis, you will have to disassemble that axis and have a look at the parts. Luckily, the Dec axis is easier to remove than the RA axis.

 

Also, here's a little known fact and warning. The grease Cave originally used inside both axes contains some sort of compound some of us (including me) are allergic too. I found this out the hard way many years ago. Do wear gloves! BTW, high temperature bearing grease, the kind used on auto front wheel bearings, makes a nice substitute and does not seem to have allergic properties.

 

Happy observing always,

 

Don



#148 CHASLX200

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Posted 15 January 2019 - 06:34 AM

Instead of adding a lock screw to the RA axis, why not simply leave the drive unplugged?

 

A long-focus 10" on the 1 1/2" shaft mount WILL jiggle quite a bit.  Planetary viewing without a drive would be agony.

I can back off the clutch and let it free float. I plan to leave the mount outside and would rather just leave the mount bear without the drive and gears. I am in the hunt for a better mount.



#149 CHASLX200

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Posted 15 January 2019 - 06:37 AM

Cheers,

 

Hmm,  I hope you removed the RA drive shaft and bearings before drilling that hole in the "polar axis" housing. Otherwise, there are probably metal chips inside the polar axis and they might eventually work their way into the bearings, particularly the lower bearing. You might think about disassembling the polar axis for a cleaning (your local astronomy club may be able to help).

 

Regarding the clutch, you should find with the telescope balanced that only light pressure from the three Allen head screws is needed to engage the drive. The clutch may still stick just a tiny bit if properly cleaned and adjusted but the main source of the backlash is the "ears" on the worm gear mount.

 

Can you isolate the jitter to the RA or Dec axis?

 

Cave used Sealmaster bearings on both axes--very much over-designed--pressed into the casting so it would be odd that the Dec shaft would loosen up in its bearings. Perhaps, somehow, the bearings went bad. I wonder if some sort of horrible mistreatment (like dropping the mount repeatedly) somehow flattened or dimpled some of the bearing surfaces? Unfortunately, if indeed the problem seems to be in the Dec axis, you will have to disassemble that axis and have a look at the parts. Luckily, the Dec axis is easier to remove than the RA axis.

 

Also, here's a little known fact and warning. The grease Cave originally used inside both axes contains some sort of compound some of us (including me) are allergic too. I found this out the hard way many years ago. Do wear gloves! BTW, high temperature bearing grease, the kind used on auto front wheel bearings, makes a nice substitute and does not seem to have allergic properties.

 

Happy observing always,

 

Don

The shaft was removed for drilling.  Like i said both axis free spin like a dream. These mounts are just maxed out with even a 10".  I can take the saddle and spin it like a top.  So there is no problem with the RA and DEC bearings or motions. It just when you focus you get the jitters.



#150 KentTolley

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Posted 15 January 2019 - 11:41 AM

My 10" f/6.8 jittered the first time I put it all back together after taking it all apart to clean, lube and paint it.  I found a loose bolt holding the Dec housing to the polar axis and tightened it and then hit the wrench with a rubber mallet a few times.  You may have a loose screw somewhere.  wink.gif

 

The number of possible failures in Caves mount is limited.  My tube is 8" longer than yours and damps out after ringinginging.  You have to get all the backlash out and adjust the clutches.

 

If you swapped out the tube elements (focuser, spider, mirror cell, etc.) then it's a good chance your tube is not correctly balanced by that tube weight.


Edited by KentTolley, 15 January 2019 - 03:09 PM.



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