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LX90 8" - Moving finderscope or adding extra accessory mounting points?

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#1 summetj

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Posted 28 February 2024 - 09:58 PM

New LX90 8" SCT owner here.    I'm interested in moving the finder-scope mount (from the top left to top right) and would also be interested in adding a secondary mounting point for a laser pointer.

Anybody have suggestions?  I'm comfortable removing parts and drilling/tapping mounting holes, but would prefer to follow a "known easy" procedure.

 

If I had to guess, the procedure would be to remove the OTA from the forks, remove the SCT ring and focusing knob, then remove the black cover from the back, and then drill/tap extra mounting holes in it. But I'd prefer if somebody has a website/procedure/youtube video where it's been documented already......

 

top-view.jpg

 

Thanks,

Jay



#2 MikeBY

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Posted 29 February 2024 - 12:12 AM

No No No!!

 

For a simple laser pointer:

Use one of the other existing screws, or

Attach the laser to the finder scope ring assembly (stack on the finder scope) or

Change the finder scope mount to a dual finder mount or

Velcro tabs or

Mount an upper accessory rail using existing screw locations and radius brackets. 

 

NEVER Defork the OTA unless you're moving the OTA to a new mount. 

 

NO, to removing the rear of the scope as the entire mirror assembly is still attached to it. You'll have to re align the optics

 

No to drilling holes unless it's a last resort,  and this isn't it. You should find that an existing pair of screws have the correct spacing for another finder mount, but laser pointers are a different thing. I'd just stack it on the finder scope. 

 

An accessory rail is overkill for a pointer. It is useful to piggy back a camera or wide field refractor. 


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#3 Pedro724

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Posted 29 February 2024 - 02:14 AM

Hi mate, my LX90 10” has two finder scopes on it, left and right. One has 90 degree on it when the OTA is vertical etc. the OTA had screws already there and it was simply a question of taking them out, fitting the mounting plate and screwing them back in. Simples. Totally agree with Ranger 4 - no to all the things you were contemplating lol.will share piccies when its next set up.


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#4 summetj

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Posted 29 February 2024 - 09:09 AM

Ok, so don't disassemble, got it!

I really wanted to move the finderscope to the other side (stay on the top, but move it to the right side to position it better for my left eye) but there are only 3 screws (seen in the photo above) which I assume hold the back to the tube (there are a similar set of 3 screws on the bottom).  The only extra screws are where the finderscope is currently mounted (on the left side of the top of the OTA).

Of the three top screws the far right one is a #8-32 machine screw that is 0.36" long with a 3/32 hex head. (assume all six semetrical screws are the same, but only removed one).

 

Just wondering what all these connect together (I assume the tube to the back assembly?) and if there are any things I should be careful of when removing/replacing? No backing plate audibly fell off when I removed one to check size, but I don't want to remove more than one at a time just in case ;>   

I'll probably end up replacing one of these screws with one that is longer to account for whatever I mount between screw head and back assembly.  This will work fine for a laser, but they are not spaced properly for the finderscope mount, so I guess moving it may not happen.



#5 summetj

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Posted 29 February 2024 - 09:33 AM


Change the finder scope mount to a dual finder mount or

I'm interested...do you have a link to a "dual finder mount" that works with the Meade LX style finderscope mount?  

BTW- What is the name / google search term for searching for compatable things that plug into the "inverted T" mounting plate that came on the LX90-8?
 

mount-profile-small.jpg finderscope-base-small.jpg



#6 Skywatchr

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Posted 02 March 2024 - 06:59 PM

New LX90 8" SCT owner here.    I'm interested in moving the finder-scope mount (from the top left to top right) and would also be interested in adding a secondary mounting point for a laser pointer.

Anybody have suggestions?  I'm comfortable removing parts and drilling/tapping mounting holes, but would prefer to follow a "known easy" procedure.

 

If I had to guess, the procedure would be to remove the OTA from the forks, remove the SCT ring and focusing knob, then remove the black cover from the back, and then drill/tap extra mounting holes in it. But I'd prefer if somebody has a website/procedure/youtube video where it's been documented already......

 

attachicon.gif top-view.jpg

 

Thanks,

Jay

There is no "magic genie" to let out if you disassemble the optical tube.  You can remove the corrector plate (being sure to mark it's orientation), then remove the focusing mechanism, then remove the primary mirror.  Then remove any grease so any drill shavings don't become embedded in it.  Then drill/tap and holes in the rear cell you like. Then thoroughly clean everything before reassembly.  Use fresh "medium" Damping Grease to lube the mirror slide/baffle tube. CAUTION: Be very careful of screw lengths so they do not touch the primary mirror.

There is no need to de-fork it at all.  If you do, then you will have to properly re-align the forks for accurate go-to.

 

I never had this particular LX90 apart, but I have had several other Meade SCT scopes apart.



#7 summetj

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Posted 24 March 2024 - 07:38 AM

rings-on-finderscope-1x1-small.jpg

Ok I ended up 3D printing attachment rings to connect my laser pointer to the finderscope.  Just with generic rings the laser pointer beam as within the FOV of the finderscope, and I was able to dial things in by varying the height of the rings slightly. With a 9mm separation on the front and a 10.5 on the back I was able to get the green dot very close to the crosshairs, so I generally don't even need to use the finderscope to get objects into my eyepiece.

 

3D / STL files are located here: https://www.thingive...m/thing:6547150

 

I expect the STL's will work with any meade 8x50 finderscope of the same era as my Meade LX-90 8".  I have also included the SCAD file, so you could edit the diameter of the ring for the finderscope or laser pointer to work with any other sized OTA/Finderscope/cylindrical laser pointer.

 

The specific laser pointer I'm using which works well can be found at this amazon affiliate link: https://amzn.to/43y7UpV

Here is a video showing the mount in action:

https://www.youtube....h?v=uJ5DuQi3M2g

 


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#8 dcaponeii

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Posted 01 April 2024 - 08:09 AM

I replaced the existing bracket with this instead.

 

 

Attached Thumbnails

  • IMG_5758.png


#9 summetj

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Posted 01 April 2024 - 07:57 PM

I replaced the existing bracket with this instead.

Nice, thanks for the pointer.  Did your telescope have a vixen style mount for the finderscope already, or did you also install a vixen mount onto the scope?  (Mine has something that looks  like an inverted T, probably Meade specific.....)



#10 dcaponeii

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Posted 02 April 2024 - 03:37 PM

Nice, thanks for the pointer. Did your telescope have a vixen style mount for the finderscope already, or did you also install a vixen mount onto the scope? (Mine has something that looks like an inverted T, probably Meade specific.....)


I cobbled a mount for the pointer by cutting the scope (gun) side of the ring mount off then epoxying the stub into a block of hardwood cut to match the shape of the vixen cross-section. The pointer is light enough that there isn’t a problem with flexure. The laser pointing adjustment knobs had enough span to handle the alignment with the FOV of my finder scope. I only use the pointer to get close then I find tune with my finder which is a 135mm SLR lens with an ASI485MC imaging through it.
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#11 summetj

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Posted 02 April 2024 - 05:09 PM

I cobbled a mount for the pointer by cutting the scope (gun) side of the ring mount off then epoxying the stub into a block of hardwood cut to match the shape of the vixen cross-section. The pointer is light enough that there isn’t a problem with flexure. The laser pointing adjustment knobs had enough span to handle the alignment with the FOV of my finder scope. I only use the pointer to get close then I find tune with my finder which is a 135mm SLR lens with an ASI485MC imaging through it.

 

It sounds like your scope body had a vixen dovetail holder/mount already installed. Unfortunately mine has some type of Meade specific "inverted T" adapter.  I'll probably just stick with what I have for now, but maybe eventually swap it out for a vixen dovetail mount as all of the current accessories appear to use that.
 



#12 dcaponeii

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Posted 02 April 2024 - 05:43 PM

It sounds like your scope body had a vixen dovetail holder/mount already installed. Unfortunately mine has some type of Meade specific "inverted T" adapter. I'll probably just stick with what I have for now, but maybe eventually swap it out for a vixen dovetail mount as all of the current accessories appear to use that.


Not true. I got the appropriate mount at the same time and simply swapped it for the Meade T-style mount. That part was trivial.

#13 summetj

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Posted 02 April 2024 - 06:48 PM

Not true. I got the appropriate mount at the same time and simply swapped it for the Meade T-style mount. That part was trivial.

Nice, do you have a link to the source for the vixen dovetail mount that matches the LX90-8" tube curve and matches the hole spacing?



#14 dcaponeii

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Posted 02 April 2024 - 07:21 PM

Nice, do you have a link to the source for the vixen dovetail mount that matches the LX90-8" tube curve and matches the hole spacing?


Not handy but it was same vendor as the triple mount if I recall. I think I had to widen the hole spacing on the bracket just a touch.


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