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Celestron C14 focuser is stuck

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#26 gnowellsct

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Posted 07 May 2018 - 04:20 PM

[quote name="Mark Bailey" post="8564249" to so the dovetail needs to be slid in not placed and then clamped. Anyway, it is up for now and I think I will try taking the corrector plate off while it is still mounted.

Mark[/quote]

Old school consider replacement with losmandy or Astro-physics saddle, make sure it's tilt in.

Good luck on dissection. Put something soft under ota opening and store corrector safely.

If it's any consolation market value is probably around $2k so at least you're not pulling apart a 6k edge.
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#27 gnowellsct

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Posted 07 May 2018 - 04:27 PM

Something comes to mind. I remember once I tried disassembly from rear and I don't think I got the right screws in on the rear casting, or I did the reassembly in the wrong order. Anyhow one of casting-to-tube screws was interfering with mirror movement. The only detail I remember was thinking I was an idiot and fixing it. Something about this incident convinced me that the ONLY disassembly protocol is from the front.
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#28 gnowellsct

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Posted 07 May 2018 - 04:30 PM

If your dad did a rear disassembly maybe he fell in same sand trap. If that's HIS paramount and he was imaging he might have DELIBERATELY tried to prevent mirror movement. The mystery is that if he did a mod like that he would have needed an aftermarket focuser on rear.
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#29 gnowellsct

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Posted 07 May 2018 - 04:32 PM

I think I tried rear disassembly hoping to replace handles on rear of tube and after I got to a certain point decided the game was not worth the candle.
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#30 gnowellsct

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Posted 07 May 2018 - 04:35 PM

I'm not sure but the diagonal to visual back may not be standard. There may be a mod there.
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#31 Mark Bailey

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Posted 07 May 2018 - 04:41 PM

gnowellsct. It is dad's Paramount. I have been wondering the same thing, if he did something to fix the mirror. He has a RoboFocus on the TEC 140 but I see no evidence of it being used on the SCT. Maybe not the right kind of focuser for what you are talking about. I think Dad must have had an Orange Tube C14 originally because he also has stowed away a Thomas Mathis Company fork mount. You could mount a car on that thing. I wanted to try out the old mount but the fittings are not the same as on this OTA in question so he apparently never mounted this one on the fork mount. 

 

That does help to know about the market value. But, on the other hand, I think the nervous adrenaline helped me clean and jerk the thing into position.

 

Here is my dumb story. I was so nervous about the process of getting the OTA up into the Paramount that I spent all my time making sure it was going to go if I got it up there. Still, it took maybe 8 tries over time (had to wait for muscle recovery). I finally got it and sat down to marvel at myself. Then I proudly homed the mount . . . and realized I put the scope in upside down.



#32 Mark Bailey

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Posted 07 May 2018 - 04:45 PM

Telling that last story points out that the scope did go through a lot of gymnastics recently. Nothing untoward or worrisome happened, but it did get jostled around quite a bit.



#33 davidmcgo

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Posted 07 May 2018 - 04:46 PM

The two partially threaded knobs are definitely the shipping screws and with them out there isn't anything stock that should prevent the mirror from moving.

 

From your picture of the exposed lead screw, (threaded rod), it does look like the mirror is all the way to the rear, and it should be able to slide forward a few inches or so.

 

Double check that no screws from finder, dovetail, or rear cell casting are impinging on the edge of the mirror or protruding behind it, you will want a bright flashlight and sight around from near the edge of the corrector looking at corresponding edge of the mirror, since they may not protrude past the coated face and can still be causing an issue.

 

There was one mod that Software Bisque sold for a while which added a locking collar around the primary baffle and mirror carrier that required accessing the inside of the telescope to tighten a set screw to eliminate mirror shift for imaging.  If there are a couple of dust plugs on the side of the tube (they'd be on shiny painted part a few inches ahead of the rear cell casting), pop those off and shine in a light and see if there is one of those installed.  If so, just a matter of getting a long hex key and loosening the hex screw.  I mention this since there appear to be two circular plugs in picture 2 of 4 in the post on page 1 about where I would expect if it had this mod.

 

See page here: http://www.skyimager...irror-lock.html

 

 

 

Dave


Edited by davidmcgo, 07 May 2018 - 04:50 PM.

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#34 Mark Bailey

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Posted 07 May 2018 - 04:47 PM

I'm not sure but the diagonal to visual back may not be standard. There may be a mod there.

There was also a reducer in there.



#35 Mark Bailey

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Posted 07 May 2018 - 05:09 PM

There was one mod that Software Bisque sold for a while which added a locking collar around the primary baffle and mirror carrier that required accessing the inside of the telescope to tighten a set screw to eliminate mirror shift for imaging.  If there are a couple of dust plugs on the side of the tube (they'd be on shiny painted part a few inches ahead of the rear cell casting), pop those off and shine in a light and see if there is one of those installed.  If so, just a matter of getting a long hex key and loosening the hex screw.  I mention this since there appear to be two circular plugs in picture 2 of 4 in the post on page 1 about where I would expect if it had this mod.

 

See page here: http://www.skyimager...irror-lock.html

 

 

 

Dave

Whoa, Dave!! That is almost certainly it. gnowellsct guessed that something was locking the mirror and it sure seemed like it to me. Sure enough there are a couple of dust plugs and a collar in there. Somehow the dust plugs never registered with me. I did see those hex heads with the flashlight and wondered if they might be set too tight but didn't know it was a mod.

 

Now to find a long enough hex head. Dad had a a weird tool I saw somewhere along the way that is probably it. Somewhere.



#36 Mark Bailey

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Posted 07 May 2018 - 05:24 PM

Found the tool. That was it. I am shaking my head. Might have figured it out after the fact but you gentlemen saved me the tear down for no reason. Great work.

 

Yay, Cloudy Nights. Thanks to all.


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#37 davidmcgo

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Posted 07 May 2018 - 05:28 PM

Glad to have helped!

 

Dave


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#38 Mark Bailey

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Posted 07 May 2018 - 05:33 PM

Great signature quote, too, Dave. Love it. Answers that question of why we climb this mountain. Thanks again.



#39 gnowellsct

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Posted 07 May 2018 - 05:51 PM

 

 

There was one mod that Software Bisque sold for a while which added a locking collar around the primary baffle and mirror carrier that required accessing the inside of the telescope to tighten a set screw to eliminate mirror shift for imaging.  If there are a couple of dust plugs on the side of the tube (they'd be on shiny painted part a few inches ahead of the rear cell casting), pop those off and shine in a light and see if there is one of those installed.  If so, just a matter of getting a long hex key and loosening the hex screw.  I mention this since there appear to be two circular plugs in picture 2 of 4 in the post on page 1 about where I would expect if it had this mod.

 

See page here: http://www.skyimager...irror-lock.html

 

 

 

Dave

SWEET JEEZUS YES!!!! That would make sense.  Good memory!  Those were popular for a while!

 

And also check to see if that diagonal comes off ok and nothing is going on there.  GN


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#40 Mark Bailey

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Posted 07 May 2018 - 06:20 PM

GN- Will do. You were on the cusp if figuring this out. Thanks for the help. -Mark



#41 Eddgie

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Posted 07 May 2018 - 06:34 PM

Wow, great save, CN members! I had never heard of this mod...


Edited by Eddgie, 07 May 2018 - 07:18 PM.

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#42 Magnus Ahrling

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Posted 07 May 2018 - 07:13 PM

I have read this thread and I am so impressed what a Great forum this really is.So many prepared to give a helping hand waytogo.gif "You never walk alone"

 

Magnus


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#43 PETER DREW

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Posted 07 May 2018 - 07:14 PM

Good result!
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#44 gnowellsct

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Posted 07 May 2018 - 07:48 PM

GN- Will do. You were on the cusp if figuring this out. Thanks for the help. -Mark

Is that a confirm Mark?  Did you check?  GN  EDIT: Never mind, scrolled up and saw you'd found it.


Edited by gnowellsct, 07 May 2018 - 07:50 PM.

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#45 gnowellsct

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Posted 07 May 2018 - 07:52 PM

There was also a reducer in there.

Of course.  He was doing the pre-fastar imaging rigamarole getting the scope down to f/7 or so.  And he had the tracking accuracy to do that.  You should post a picture of two that he took if you find any.    I could see that there was something extra in that rear port.  -GN


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#46 gnowellsct

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Posted 07 May 2018 - 07:57 PM

And I remembered what I figured out about the necessity of front only entry, even if the goal is to remove the rear casting from the OTA.  The screws in the back have nuts, and after you unscrew them the nuts fall into the OTA.  When you want to replace the nuts the mirror is in the way unless you have a very fancy tool and don't mind working close to a finely figured glass.  So to get the rear screws in you have to have the primary out.

 

I still don't remember how I jammed the focus mechanism, I just remember something like that happened.  Greg N


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#47 Mark Bailey

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Posted 07 May 2018 - 08:04 PM

Of course.  He was doing the pre-fastar imaging rigamarole getting the scope down to f/7 or so.  And he had the tracking accuracy to do that.  You should post a picture of two that he took if you find any.    I could see that there was something extra in that rear port.  -GN

Greg- Dad seems to be sort of a catch and release guy when it comes to pics. He took his website down concurrent to asking me take his observatory/magnum opus over. There are no images on his observatory PC. I asked him about it and he just shrugged. His memory is playing old man tricks and he hates not being able to recall right away. I expect some day I will find a treasure trove of images on one of his external drives. 


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#48 gnowellsct

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Posted 07 May 2018 - 08:48 PM

Greg- Dad seems to be sort of a catch and release guy when it comes to pics. He took his website down concurrent to asking me take his observatory/magnum opus over. There are no images on his observatory PC. I asked him about it and he just shrugged. His memory is playing old man tricks and he hates not being able to recall right away. I expect some day I will find a treasure trove of images on one of his external drives. 

do a search using his name or the name of his observatory.  He might have an on-line hoard.  He's lucky to have a son who's into astronomy.  My kid has been out with me since he was five and has no interest what so ever.  It's all Overwatch.  If you don't know what it is, don't bother to find out.  Well I'm not being fair.  He's got a sensitivity to what this stuff is all about and will take a look.  But he's got no particular interest of his own in it, which I suppose is OK.  He has to find his own path.  GN


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#49 Mark Bailey

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Posted 07 May 2018 - 09:15 PM

do a search using his name or the name of his observatory.  He might have an on-line hoard.  He's lucky to have a son who's into astronomy.  My kid has been out with me since he was five and has no interest what so ever.  It's all Overwatch.  If you don't know what it is, don't bother to find out.  Well I'm not being fair.  He's got a sensitivity to what this stuff is all about and will take a look.  But he's got no particular interest of his own in it, which I suppose is OK.  He has to find his own path.  GN

Another good idea to search the net, but not finding anything yet.

 

And Patience, Dad. When my father got his first C8 I was probably 25. I saw Halley's Comet with him when I was 30. But I had family and career and didn't start to get into it myself until I was maybe 55. I am 62 now. My 30 year old son is about as interested as I was. Likes it but not into yet. Same for 34 year old daughter.

 

I am not close to my dad, but we have this hobby in common. It is interesting to learn more about him through learning the observatory and seeing his choices. Grateful for the late gift of it all.


Edited by Mark Bailey, 07 May 2018 - 09:16 PM.

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#50 gnowellsct

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Posted 07 May 2018 - 10:06 PM

Another good idea to search the net, but not finding anything yet.

 

And Patience, Dad. When my father got his first C8 I was probably 25. I saw Halley's Comet with him when I was 30. But I had family and career and didn't start to get into it myself until I was maybe 55. I am 62 now. My 30 year old son is about as interested as I was. Likes it but not into yet. Same for 34 year old daughter.

 

I am not close to my dad, but we have this hobby in common. It is interesting to learn more about him through learning the observatory and seeing his choices. Grateful for the late gift of it all.

If I have to wait for my kid to be 62 I'm gonna be.....107.  No way.  


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