57 replies to this topic

[exmedia]

DEFORKING MY MEADE 8" LX90

When I went looking for information on how to defork my LX90 I found quite a lot, but not the step-by-step instructions I was hoping for. So, I decided to document what I did in case it may help someone else.

What follows are the steps I took to remove my 2006 Meade 8” LX90 from its fork mount. Other LX90s may be different, so please take that into account before you set out to modify your own LX90.

It's probably a good idea for you to read through the instructions before beginning. The project isn't really all that hard, but it's good to know what you're getting into. Here's what you'll need:

• Full set of SAE Allen wrenches (hex key)
• Phillips head screwdriver
• Penetrating oil (Liquid Wrench)

Preparation: Place your LX90 in the position shown, using a box or equivalent to support the base. Other positions may be used; this is one that was suggested to me and which worked fine. The goal here is to provide access to the left fork arm (the one without the alt clutch).

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There are three screws toward the rear of the OTA. These three screws, along with the ones on the opposite side of the OTA, are all that secure the telescope to the Alt-Az mechanism. Begin by removing all six screws. You will need a 9/64” Allen wrench.

If you’re extremely lucky, the scope tube will now slide out of its trunnion carriers (http://en.wikipedia.org/wiki/Trunnion) and you’ll be done. Be very careful! You can easily scratch the paint. More likely, though, it won’t budge and you’ll need to continue.

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This is a view of the inside of the left fork arm. Remove the four screws using a 3/32” Allen wrench.

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Next, remove the two Phillips screws at the base of the left fork arm.

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Unscrew and remove the knob.

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Remove the three, 3/32” Allen screws.

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You can now remove the plastic cowling from the left fork arm.

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At the base of the left fork arm is an angled plastic plate from which you previously removed the Phillips screws. Grasp and slide this plate out. It may take a little force.

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You now have access to the four Allen bolts which hold the fork arm to the base. Loosening these will allow you to spread the fork arm slightly so the OTA may be removed. These are most likely very tight, and may require application of penetrating oil (like Liquid Wrench) to help break them free. Penetrating oil needs to soak in to be effective; it can take up to 24 hours before you'll be able to break loose the bolts. Be careful not to get the penetrating oil anywhere other than around the bolts.

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Once the bolts are loose you should be able to spread the left fork arm slightly and slide the OTA from its trunnion carriers. Reverse all the above steps to put the left arm back together. Caution: Any screws you put back into the OTA should be screwed in only to the depth they were before. Any further in may place them in the optical or mirror path.

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[exmedia]

And here is the final result on a Celestron AVX mount (Frankenscope!). Total weight of the OTA with finder scope, Telrad, ADM ring mounting bar, Vixen dovetail bar, diagonal and eyepiece is 15 lbs. Good luck!

Richard

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[psyhiker]

Excellent instructions...thanks for posting...

[Brian Risley]

Only comment I might add since it is an issue with Celestrons is to make sure any screws you put back in the OTA from the mount holder do not go too far in and obstruct the mirror path. Same holds true for any accessory added/removed from the OTA.

Brian

[exmedia]

Only comment I might add since it is an issue with Celestrons is to make sure any screws you put back in the OTA from the mount holder do not go too far in and obstruct the mirror path. Same holds true for any accessory added/removed from the OTA.

Brian

Got it. Good point. I made the change.

Richard

[Matthew Ota]

Another Frankenscope....

[Dinomonaco]

Excellent procedure! Just came across this article because I have an ACF 8" LX90.

Love the OTA , but ready to move it onto a GEM.

thanks.

ps. Wondering if I can sell the fork. Has the GPS module and Audiostar controller.

 

regards,

 

dino

[d33d0gg]

I am sure the fork would sell quite easily, as it contains a bunch of goodies!

[BLACKDRAGON]

Many thanks for this video as it gave me the basic idea and confidence to de-fork my LX200 12 inch scope.   Knowing what size Allen wrenches I needed for a great help, although I found that in what I thought was my vast and comprehensive collection of Allen Keys I didn't have a 9/64" one!!!!  So I had to send for a set which, thankfully, arrived the next day.   I did unscrew the three screws on either of the scope as advised and, of course, the Telescope didn't budge!!!    So I made a mug of Tea, and looked at the base. There were 4 large bolts on either side of the base of each Fork right in the corner. The inner bolts were made awkward by being protected by the base strengthening vanes.   They eventually surrendered to a bit of torque and came loose with an alarming crack!, but they came loose.   Once all 4 bolts were slackened right off the Telescope slid out of the forks easily without any damage or scratches.    The sense of relief was immense and the Telescope is now safely in a large plastic wheeled box and lying on a bed of foam rubber.   The fork needs putting back together and will go up for sale when I've put a dovetail on the scope.    

[OzAndrewJ]

Just another option if the forks arent too tight.

You can use the quickgrip style F clamps

http://www.bunnings....-clamp_p5860115

to preload the forks thus springing them out far enough to release the OTA.

The ends of many clamps are reversible, ie they can clamp like normal

or push apart :-)

 

Doing this also means you dont affect the orthogonality of the DEC axle

 

Andrew Johansen Melbourne Australia

[junomike]

Many thanks for this video as it gave me the basic idea and confidence to de-fork my LX200 12 inch scope.   Knowing what size Allen wrenches I needed for a great help, although I found that in what I thought was my vast and comprehensive collection of Allen Keys I didn't have a 9/64" one!!!!  So I had to send for a set which, thankfully, arrived the next day.   I did unscrew the three screws on either of the scope as advised and, of course, the Telescope didn't budge!!!    So I made a mug of Tea, and looked at the base. There were 4 large bolts on either side of the base of each Fork right in the corner. The inner bolts were made awkward by being protected by the base strengthening vanes.   They eventually surrendered to a bit of torque and came loose with an alarming crack!, but they came loose.   Once all 4 bolts were slackened right off the Telescope slid out of the forks easily without any damage or scratches.    The sense of relief was immense and the Telescope is now safely in a large plastic wheeled box and lying on a bed of foam rubber.   The fork needs putting back together and will go up for sale when I've put a dovetail on the scope.    

Be sure to update your other thread with pics If possible!

 

Mike

[RedLionNJ]

Hi - adding to this thread as it seems most relevant..

 

I'm trying to do the same (deforking, replacing my SCT OTA on a GEM) but I have a 12-inch LX200ACF.

 

 

Removing the 'third' screw on each side of the scope is the issue for me.

 

With the slightly-larger mount for the 12-inch, that third (front-most) screw is partly obscured by the rounded part of the mount itself. I can't get a wrench in to loosen it without what appears to be some substantial subsequent disassembly of both fork arms. I *really* want to avoid that much time and effort if at all possible.

 

Anyone have any ideas? Please....?

 

 

[SamTheMan]

Yesterday, I  acquired a complete LX50.  It came with an Autostar controller.  I know absolutely nothing about this LX50.  Does it have goto built in?  I need to find a good manual also, in case anyone happens to have their in PDF format.

 

I'd also like to know what kind and where I can buy the dovetail rail/bar? that is attached to the tube.  I'd like to mount this on my LXD55.

thx

SamTheMan

samdhunt@outl;ook.com

text 253 315-4542

[Piet Le Roux]

Thanks for the instructions Richard,

I was wondering what did you do with the LX90, mount I am sure there is a market for Dec and Az drive spares but my interest is in the two 154 tooth gears. I have LX90 that was delivered with 156 tooth gears and although it works fine if you adjust the gear ratio appropriately I would like to purchase them if they are still available.

Regards  

Edited by Piet Le Roux, 04 October 2020 - 01:02 AM.

[Piet Le Roux]

Yesterday, I  acquired a complete LX50.  It came with an Autostar controller.  I know absolutely nothing about this LX50.  Does it have goto built in?  I need to find a good manual also, in case anyone happens to have their in PDF format.

 

I'd also like to know what kind and where I can buy the dovetail rail/bar? that is attached to the tube.  I'd like to mount this on my LXD55.

thx

SamTheMan

samdhunt@outl;ook.com

text 253 315-4542

That is interesting : as far as I know the LX50 did not have a Autostar controller and were not goto. I have seen mods to make then goto and I have seen old classic LX200 scopes being upgraded to use Audiostar  controllers, so I think it is possable that your LX50 has been upgraded. Here is a manual for the standard LX50.

https://www.manualsl...Meade-Lx50.html

[DSOGabe]

A similar tutorial for the LX200 would be appreciated. The fork arms are so massive that accessing the screws in next to impossible