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Just experienced an "uh-oh" with my Meade 14

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#1 Pat Rochford

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Posted 14 November 2017 - 02:49 PM

A little background - I've had this 14" Meade for 13 years.  I de-forked it a few years ago and placed it on an HDX110 (EQ8) German mount (in an observatory), primarily because I use a photoelectric photometer and was limited to access in the northern sky (photometer is long and bottomed out on drive base of the LX200 fork mount).  Moving the scope between variable and comparison stars is a relatively short distance, so moving it back and forth using the directional keys is quicker than doing a GOTO.

 

That being said, the only issue has been occasionally finding myself in an awkward position finder scope wise, so I decided to add another finder 180 degrees from the existing one.  I purchased a 6 x 30 right angle finder the other day and decided to mount it this morning.  Everything was going well until it suddenly wasn't.

 

On the side of the rear cell, midway between the mirror lock knob and focuser knob is a 3/4" x 1 3/4" plate, held in place with two #10 cap screws.  The screws have always been just finger tight and upon removing one of them I could see a threaded backing plate.  There doesn't seem to be any particular use for this plate so I thought it would make a good location for the second finder.  I then removed the second screw so I could determine whether the finder would be better positioned in the hole closer to the corrector or closer to the backside.  I chose the most forward hole, then placed the finder base against the cell and inserted the screw (one screw would be sufficient since the finder is very light).

 

That's when things kind of turned sour.  As soon as the screw reached the backing plate, it (the backing plate) dropped down inside the cell housing.  I had made the (incorrect) assumption that the backing plate was affixed to the housing, but obviously it was only 'stuck' there by so many years of contact with said housing.

 

If you're still reading (thank you), the problem I now have is a loose plate flopping around inside the cell.  I doubt it'll interfere with anything, but the thought (and sound) of it moving around in there is bothering me.  It appears that the only means of access would be through the removal of either the mirror lock knob or the focuser knob.  I've never had reason to remove either and am somewhat hesitant about attempting either without consulting someone who's (successfully) done one or the other. 

 

By any chance, have any of you experienced this before?  Or had reason to work on the mirror lock or focuser?  If so, I'd be very grateful for any suggestions.  Many thanks in advance. 



#2 Ishtim

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Posted 14 November 2017 - 03:39 PM

I read your post.  I have an 14" LX200 (circa 2004) but not sure about it having the plate you describe.  Here's a link to a picture that shows the rear cell (like mine) without the plate.

https://www.highpoin...ta_back_1_1.jpg

 

I have had my focuser knob on/off a couple of times (years ago).  The focuser know is actually a "drum" or cylinder shaped gear that rides on the flat "flywheel" gear that moves the mirror back and forth.  It may have been here where someone documented the disassembly of an LX200, I think it was a 14".

 

I am curious about this "plate"...

 

BTW, the article I was referring to is on AM.  https://www.astromar...?article_id=524
 


Edited by Ishtim, 14 November 2017 - 03:41 PM.


#3 PowellAstro

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Posted 14 November 2017 - 06:06 PM

I've had mine completely apart both the focuser and mirror lock. Don't remember any thing I would call a plate. Can you post a picture or two?

#4 Pat Rochford

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Posted 14 November 2017 - 07:20 PM

Inkedlx200_14_ota_back_1_1_LI.jpg

 

Thanks for the response guys, here is the plate I was referring to.  Just trying to find out if removing either of these knobs might provide access to get the backing plate of this piece fished out. 


Edited by Pat Rochford, 14 November 2017 - 07:31 PM.


#5 PowellAstro

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Posted 14 November 2017 - 08:58 PM

The focus lock knob will provide the largest hole. Once you take the three screws out, tilt the lock knob to the left and move as far to the right after tilting to clear the gear.

#6 Steve D.

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Posted 15 November 2017 - 05:45 AM

Pat, is the loose plate on the inside of the tube made of steel?  If so, and if it’s small enough, maybe feeding a string with a magnet securely attached through the visual back and baffle tube might be able to grab it and pull it out.


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#7 P26

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Posted 15 November 2017 - 10:07 AM

Hello Pat,

 

I have the first 14" shipped.  And have the same little plate that you've highlighted.  Never really noticed it before.  And have no idea as to what it is.

 

These early fourteens weighed 125#.  Later fourteens weighed 110#.  I've speculated that Meade just used heavier castings on the early production (in an effort to balance the heavy nose-heavy scope).  And that they then went to a lighter casting to improve portability as a trade-off on balance.

 

Every part that you add to a product costs more money. So there's a reason for that plate being there rather than just the 2 screws thru the casting.  I've not had my 14 completely disassembled, and why those two screws would need a backing plate is a puzzle indeed.  It suggests that they're screwed into a heavy weight.  And there's a slight chance that instead of the heavier casting there's a counterweight in there.

 

You can't live with a loose whatever in there.  You're probably going to have to remove the corrector plate and the primary mirror to get at whatever.

 

Regrets,

 

Pete

 



#8 rmollise

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Posted 15 November 2017 - 12:53 PM

A little background - I've had this 14" Meade for 13 years.  I de-forked it a few years ago and placed it on an HDX110 (EQ8) German mount (in an observatory), primarily because I use a photoelectric photometer and was limited to access in the northern sky (photometer is long and bottomed out on drive base of the LX200 fork mount).  Moving the scope between variable and comparison stars is a relatively short distance, so moving it back and forth using the directional keys is quicker than doing a GOTO.

 

That being said, the only issue has been occasionally finding myself in an awkward position finder scope wise, so I decided to add another finder 180 degrees from the existing one.  I purchased a 6 x 30 right angle finder the other day and decided to mount it this morning.  Everything was going well until it suddenly wasn't.

 

On the side of the rear cell, midway between the mirror lock knob and focuser knob is a 3/4" x 1 3/4" plate, held in place with two #10 cap screws.  The screws have always been just finger tight and upon removing one of them I could see a threaded backing plate.  There doesn't seem to be any particular use for this plate so I thought it would make a good location for the second finder.  I then removed the second screw so I could determine whether the finder would be better positioned in the hole closer to the corrector or closer to the backside.  I chose the most forward hole, then placed the finder base against the cell and inserted the screw (one screw would be sufficient since the finder is very light).

 

That's when things kind of turned sour.  As soon as the screw reached the backing plate, it (the backing plate) dropped down inside the cell housing.  I had made the (incorrect) assumption that the backing plate was affixed to the housing, but obviously it was only 'stuck' there by so many years of contact with said housing.

 

If you're still reading (thank you), the problem I now have is a loose plate flopping around inside the cell.  I doubt it'll interfere with anything, but the thought (and sound) of it moving around in there is bothering me.  It appears that the only means of access would be through the removal of either the mirror lock knob or the focuser knob.  I've never had reason to remove either and am somewhat hesitant about attempting either without consulting someone who's (successfully) done one or the other. 

 

By any chance, have any of you experienced this before?  Or had reason to work on the mirror lock or focuser?  If so, I'd be very grateful for any suggestions.  Many thanks in advance. 

 

 

I'm sorry to say that the most practical method of retrieving it may be to pull the primary. It's possible you can work it past the primary and into the tube itself, which would only require removing the corrector, but that may be hard to do with this big telescope. If I'm understanding you correctly, it is inside the rear cell now. You might try moving the scope to various corrector down orientations and see if you can get it past the mirror, etc.


Edited by rmollise, 15 November 2017 - 12:54 PM.


#9 BarrySimon615

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Posted 15 November 2017 - 03:20 PM

Can you see the plate at all looking for it thru the corrector plate? Was only the plate tapped or both the plate and the rear cell casting? The least "surgical" approach would be to try to work it back into place and grabbing it with the proper threaded bolt. In addition you would want to capture it in place.

I would do that this way: Tube parallel to the ground with the two holes down, have a pin up thru the hole and with small taps on the tube work the plate over toward the pin. This all assumes that your friend helping you is reliable and coherent. If you can get the plate in place with one pin, secure it with tape or something to keep it from falling out or falling in. Repeat the process for the second opening in both the tube and the plate. May be more of a challenge if the plate flipped over. You should be able to see that thru the corrector plate. You will have to get it to flip over first.

Anyway, assuming proper orientation, the second pin should have a 90 degree small bend to put some pressure on the plate so that you can resecure it thru the other hole with the button head cap screw. Once done there go back to the first hole and try to work a small amount of silicone rubber between the plate on that end and the inside of the cell wall. Once dry you can do the same for the other hole. This will allow you to fasten the finder bracket.

Time consuming, but I would try this first.

Barry Simon

#10 Pat Rochford

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Posted 15 November 2017 - 04:05 PM

Thanks again for everyone's suggestions.  To answer your questions:

 

- I appreciate the information on removing the focus knob.  It will certainly help knowing this, should that become the best method of retrieval.

 

- The outer plate is aluminum.  I'm going to assume the inner one is aluminum as well.  And the cell is, unfortunately, not threaded.  This became painfully apparent as soon as I heard the 'clunk'.  

 

- I'm 99% certain that there is no counterweight involved with this engineering mystery.  The clunk had the sound of something extremely light, hence my thinking it is identical to the outer plate.  Whatever it is, it easily slides around in the bottom of the cell.  

 

- I suppose the first thing I'm going to do is look through the corrector plate and see if I can spot it.  Don't know why that didn't occur to me when it happened - guess it was my 'doh!' moment for the week.  If I can spot it, hopefully I can tip the tube downward enough and watch it slide toward the corrector.  If it's identical to the outer plate, then it's only a sixteenth of an inch thick and should clear between the mirror and the inside of the cell.  I guess it all depends on the configuration of the casting ... hopefully no lip is involved.  If I can get it past the primary, perhaps it will only be a matter of removing the corrector.  I've heard how difficult it has been for some to remove the cell and corrector castings from Meade tubes.  Hopefully the corrector is only held with screws.

 

I'll keep everyone updated with my (hopeful) progress.  Again, thank you all for the information/suggestions so far.  If I am successful, the final step will be to find out what the #&%% Meade was thinking with this little accident waiting to happen.    

 

 



#11 Pat Rochford

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Posted 18 November 2017 - 03:38 PM

An update - I can see the backing plate through the corrector.  It is the same size as its exterior counterpart and appears to be aluminum.  If it weren't for the curvature of the rear casting, it would slide all the way to the corrector.  The center of the plate just barely makes contact with the edge of the mirror.

 

I took 72 measurements of Betelgeuse, Rigel and the sky background (J & H bands in the near IR) the other night without any issues.  It simply slides around against the back of the casting and doesn't interfere with anything.  So for now, I think I'm going to leave things just as they are.  Perhaps a lightbulb will go off one of these days and I'll figure a clever way to get it out, without having to disconnect either the locking or focusing mechanisms.    




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