Jump to content


Photo

How I deforked my 8" LX90

  • Please log in to reply
14 replies to this topic

#1 exmedia

exmedia

    Ranger 4

  • *****
  • Posts: 306
  • Joined: 26 May 2013
  • Loc: Orange County, CA

Posted 15 November 2013 - 08:30 AM

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).

Attached Files



#2 exmedia

exmedia

    Ranger 4

  • *****
  • Posts: 306
  • Joined: 26 May 2013
  • Loc: Orange County, CA

Posted 15 November 2013 - 08:33 AM

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.

Attached Files



#3 exmedia

exmedia

    Ranger 4

  • *****
  • Posts: 306
  • Joined: 26 May 2013
  • Loc: Orange County, CA

Posted 15 November 2013 - 08:34 AM

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

Attached Files



#4 exmedia

exmedia

    Ranger 4

  • *****
  • Posts: 306
  • Joined: 26 May 2013
  • Loc: Orange County, CA

Posted 15 November 2013 - 08:35 AM

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

Attached Files



#5 exmedia

exmedia

    Ranger 4

  • *****
  • Posts: 306
  • Joined: 26 May 2013
  • Loc: Orange County, CA

Posted 15 November 2013 - 08:37 AM

Unscrew and remove the knob.

Attached Files



#6 exmedia

exmedia

    Ranger 4

  • *****
  • Posts: 306
  • Joined: 26 May 2013
  • Loc: Orange County, CA

Posted 15 November 2013 - 08:38 AM

Remove the three, 3/32” Allen screws.

Attached Files



#7 exmedia

exmedia

    Ranger 4

  • *****
  • Posts: 306
  • Joined: 26 May 2013
  • Loc: Orange County, CA

Posted 15 November 2013 - 08:39 AM

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

Attached Files



#8 exmedia

exmedia

    Ranger 4

  • *****
  • Posts: 306
  • Joined: 26 May 2013
  • Loc: Orange County, CA

Posted 15 November 2013 - 08:40 AM

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.

Attached Files



#9 exmedia

exmedia

    Ranger 4

  • *****
  • Posts: 306
  • Joined: 26 May 2013
  • Loc: Orange County, CA

Posted 15 November 2013 - 08:41 AM

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.

Attached Files



#10 exmedia

exmedia

    Ranger 4

  • *****
  • Posts: 306
  • Joined: 26 May 2013
  • Loc: Orange County, CA

Posted 15 November 2013 - 08:43 AM

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.

Attached Files



#11 exmedia

exmedia

    Ranger 4

  • *****
  • Posts: 306
  • Joined: 26 May 2013
  • Loc: Orange County, CA

Posted 15 November 2013 - 08:44 AM

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

Attached Files



#12 psyhiker

psyhiker

    Explorer 1

  • -----
  • Posts: 90
  • Joined: 28 Feb 2013
  • Loc: Burbank, CA

Posted 16 November 2013 - 12:11 AM

Excellent instructions...thanks for posting...

#13 Brian Risley

Brian Risley

    Mercury-Atlas

  • *****
  • Moderators
  • Posts: 2832
  • Joined: 04 Sep 2006
  • Loc: SW Florida

Posted 16 November 2013 - 10:08 AM

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

#14 exmedia

exmedia

    Ranger 4

  • *****
  • Posts: 306
  • Joined: 26 May 2013
  • Loc: Orange County, CA

Posted 16 November 2013 - 11:39 AM

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

#15 Matthew Ota

Matthew Ota

    Hmmm

  • -----
  • Posts: 2137
  • Joined: 30 Apr 2005
  • Loc: Los Angeles, California

Posted 16 November 2013 - 03:44 PM

Another Frankenscope....






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics