22 replies to this topic

[vidrazor]

My friend recently bought the above model Meade from the big selloff at Highpoint Scientific.

 

We were trying to mount a motor mount to the unit, and could not get the the knob off. So we searched online and found some info that said the the knob needs to be turned fully counterclockwise till it stops, and then needs to be unscrewed once the focus knobs hex locking bolts are loosened.

 

What was not made a point of in that information, and much to our amazement, astonishment, and shock, is that the focus ring is the only thing that holds the primary mirror in place!

 

So no sooner than we removed the focus knob, the primary and it's focus mechanism just slid down into the tube and went crashing on to the plastic secondary hood!

After our initial shock of the event, we realize we had no choice but to take the entire unit apart, get a closer inspection of the primary, and try and figure out how to put it back together.

 

Now everything we saw online about this mentioned removing everything through the front of the scope, which we found odd, since the front element needs to be oriented in a specific manner and should best be left alone. Nonetheless, that's what we did, made a note of it's positioning and wound up removing the primary through the front.

 

Initially we thought the primary was totaled, but it turned out to be mostly grease that had gotten on the surface from it's adventure. We wound up removing the mirror from it shaft and focus link, removing any stray grease, and placing it in a dish with some dishwashing detergent, which was the protocol we found online for cleaning these mirrors, and proceeded to go through the cleaning ritual involved. When done we were quite astonished actually to find only one small spot that appears to be permanently damaged, and the rest of the mirror is fine.

 

So now the big mystery for us is to figure out how we can get the mirror, with it's focusing linkage attached, back in through the front of the tube without the linkage falling back down into the tube, and sliding into the opening the brass focus shaft goes through. Not to mention being able to see the linkage, which will be obscured by the primary, so how will we know how to properly place it is a mystery. That linkage is the flimsiest system I have ever seen for such a process, there is no way to keep the linkages locked together, the whole thing looks like an exercise in futility.

 

My gut feeling is to remove the rear plate with the primary baffle, put everything together that way, and then mount the entire rear assembly back in. However try as we might, we could not get that rear assembly (or the front one, for that matter) removed. We removed every screw we could find, and tried tapping it out from the inside with a hammer and metal rod for a tap, and that unit would not budge.

 

Soooo...

 

Does anyone know how to put these units back together? We're at a bit of a loss on this.

 

If you've read this far, thank you, and perhaps you've been though a similar nightmare with a Meade.

[Asbytec]

I wish I could help, maybe someone will. You seem to have tried everything I would have tried. I have never run across this problem. 

[vidrazor]

I wish I could help, maybe someone will. You seem to have tried everything I would have tried. I have never run across this problem. 

Yeah, I hope to find something online. Most of what we've found is for big Meades, 12s, 14s, and not all that info transfers down to the little 6.

 

It's a shame, cause the kid never got a chance to go first light with his brand new scope! I've installed motors on my C5 and C8, and of course they're entirely different animals, but the mirror assemblies aren't held in place by the focusing knob.   That's the last thing I ever expected, for the Meade to hold an entire mirror assembly in place solely by the focusing knob! That's just insane.

 

The kid's got collage classes to contend with for the moment, so we'll see if by next week we can figure out how to get the mirror back in with it's focusing mechanism attached, which hangs on to it by a wing and prayer, without it falling off the mirror and into the tube as we try to slide it back down and out through the rear opening.

[OzAndrewJ]

Gday VidRazor

Do you have a side view piccy of what you are talking about?

If there is a threaded hole in the end for a stop screw

you can use that with a guide rod to bring it through the hole.

Andrew Johansen Melbourne Australia

[vidrazor]

Gday VidRazor

Do you have a side view piccy of what you are talking about?

If there is a threaded hole in the end for a stop screw

you can use that with a guide rod to bring it through the hole.

Andrew Johansen Melbourne Australia

Well, everything is out and apart right now, but I can show you the linkage I was referring to, in the image below.

 

The mirror mounts to the metal plate on the right, and is held in place by the black plastic sleeve, which glides up and down the primary baffle. The focus knob slides into the protruding pin sticking out the side of the metal mount. There is no screw or nut to keep it from sliding off, and you have to angle the mirror to get it through the front. At least, that was the only way we could get the mirror out through the front.

 

Even if we can slide the mirror straight down, there's no way to see if you're lining the brass knob up correctly so it enters the hole in the rear of the telescope tube. At any point in that endeavor, that brass bar can slip off that pin, if it were to enter the bottom hole incorrectly, or not at all. We would then have to pull the mirror all the way out again, reinsert the brass bar into the pin, and start the process all over again. Right.

 

So that is what we have to figure out to effectively do, hopefully once. If we can do that, then we reattach the focus knob to the protruding brass sleeve, by screwing it back on and tightening down two hex screws. That focusing knob is the only thing that holds that entire assembly in place! That's what blew our minds. It was a real Whiskey Tango Foxtrot moment.

Attached Thumbnails

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[Asbytec]

So, is it possible to install only the assembly in the pic above, then slide the mirror onto the baffle? 

[OzAndrewJ]

Gday Vidrazor

Do you have piccies of the knob side of the focusser and also

the hole in the back of the casting.

That part you show looks like the focusser has been disassembled in situ ( bad )

Normally, the focusser is removed by screwing it full forwards,

then removing the 3 screws that hold the focusser to the casting.

This leaves a large hole, and then you can then pull it back a bit manually

and just slide the unit sideways off the pin.

Even if you could push that bit shown back through the current hole

you wont be able to preload it as it will just spin ( as it is a bearing )

 

Andrew Johansen Melbourne Australia

[OzAndrewJ]

actually, have a squizz at

http://karmalimbo.com/aro/mods/ota.htm

Yours wont be identical, but it shows how 99% of Meade focussers fit

 

Andrew Johansen Melbourne Australia

[Asbytec]

Gday Vidrazor

.

That part you show looks like the focusser has been disassembled in situ ( bad )

 

Normally, the focusser is removed by screwing it full forwards,

then removing the 3 screws that hold the focusser to the casting.

This leaves a large hole, and then you can then pull it back a bit manually

and just slide the unit sideways off the pin.

 

Even if you could push that bit shown back through the current hole

you wont be able to preload it as it will just spin ( as it is a bearing )

 

Andrew Johansen Melbourne Australia

So, when you remove the focusing rod, the focuser knob stays attached to the brass screw? Can he simply reattach the knob to the brass threaded part without spinning it and then reinsert it? One can imaging getting it back on the unthreaded pin might be difficult because it's impossible to see behind the mirror. But, if the mirror is in the way, can he reinstall it separately afterward? 

[OzAndrewJ]

Gday Asbytec

So, when you remove the focusing rod, the focuser knob stays attached to the brass screw?

Unless he has a weird variant, absolutely.

The whole focuuser assy, ie rod, brass journal, bearings, knob and housing

al stay together as one unit.

When removed, to reduce backlash in the focusser, you release the grub screws that hold

the alloy knob to the brass journal and tighten the fit until the bras journal is snug

but can still turn in the housing, and then retighten the grub screws.

The Peterson focus kit describes this well as al they do is replace the nylon

bearings with roller bearings, to get a tight fit with no lash

 

One can imaging getting it back on the unthreaded pin might be difficult because it's impossible to see behind the mirror

Look at the link i gave

You can see the pin through the large hole in the rear casting.

With the focusser rod extended fully, you can wiggle the pin to a position where

it just slides onto the rod and then pull it back and secure it.

If worried about the link, try this one

https://www.cloudyni.../#entry11172154

Its a link to a thread here on CN that shows the same stuff

 

Andrew Johansen Melbourne Australia

Edited by OzAndrewJ, 26 April 2025 - 10:06 PM.

[Asbytec]

Yea, those are great links. Maybe just what the OP needed. Thanks for that. I've owned several SCTs but never removed the focuser knob. 

Edited by Asbytec, 26 April 2025 - 10:26 PM.

[vidrazor]

So, is it possible to install only the assembly in the pic above, then slide the mirror onto the baffle? 

No way. It all has to go in together. There is one ray of hope, that I'll outline below.

 

That part you show looks like the focusser has been disassembled in situ ( bad )

Normally, the focusser is removed by screwing it full forwards,

then removing the 3 screws that hold the focusser to the casting.

This leaves a large hole, and then you can then pull it back a bit manually

and just slide the unit sideways off the pin.

Even if you could push that bit shown back through the current hole

you wont be able to preload it as it will just spin ( as it is a bearing )

The little 6 inch is different from those big boys. Other than the focusing knob on the outside, you're looking at the entire focusing mechanism.

 

However I've notice that if we remove the plastic sleeve that the brass shaft goes through to come out the rear, there is a larger opening. This can give us some leeway in being able to drop the assembly through the opening. Once it's through, the hardest part is done. We simply put the sleeve back on, and attach the motor mount we intended to in the first place, and never touch it again!
 

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[Asbytec]

Okay, sounds like a plan.

 

But, in the same way as the illustrations above with a larger hole, can you reinstall the focusing mechanism from the bottom? I realize that plastic sleeve will have to be dealt with before inserting the focusing rod. 

 

I've never done this, so I'm thinking out loud. 

Edited by Asbytec, 26 April 2025 - 11:10 PM.

[vidrazor]

But, in the same way as the illustrations above with a larger hole, can you reinstall the focusing mechanism from the bottom? I realize that plastic sleeve will have to be dealt with before inserting the focusing rod. 

I've never done this, so just brain farting a little. 

Yes I've thought of that too, but I don't know how well we'll be able to see in there while simultaneously trying to insert the brass shaft and trying to pin the tail on the donkey.
 

[OzAndrewJ]

Gday Vidrazor

Other than the focusing knob on the outside, you're looking at the entire focusing mechanism.

Other than the plastic sleeve held in by 3 screws.

That is the outer part of the focusser mechanism.

ie the black part in the piccies in the second link.

That black bit is actually a bushing.

The bronze inner section spins inside it and is held at each end by

axial bearings,

Study the second link, and you wil see that if you remove that black bit

and reassemble the focusser mechanism, once screwed out full

you should be able to fit it to the pin on the mirror using the leeway of the hole.

The first link shows how it should be able to be fitted when fully assembled

Andrew Johansen Melbourne Australia

[Asbytec]

 

Study the second link, and you will see that if you remove that black bit

and reassemble the focuser mechanism, once screwed out full

you should be able to fit it to the pin on the mirror using the leeway of the hole.

 

 

 

The second link shows the bushing attached to the focusing rod with the knob attached. The assembly is complete with the black bit installed. When you say, "using the leeway of the hole," I suppose you mean peeking up through the bottom and not trying to drop it in from the inside of the tube with the mirror attached. 

Edited by Asbytec, 26 April 2025 - 11:37 PM.

[OzAndrewJ]

Gday Asbytec

I suppose you mean peeking up through the bottom and not trying to drop it in from the inside of the tube with the mirror attached.

Yep.

The mirror and sled is simply fitted and pushed back

The focusser assy ( with rod fully extended ) is then just

poked through the large hole in the casting as far as you can

with the threaded rod on the side of the hole.

There should be enough lateral movement then to fit the

focusser over the pin on the sled and centre it then do up the three screws.

If that proves impossible, then just fully unscrew the inner threaded rod

from the brass bearing. Use some tweezers etc to fit it to the sled then pull it back through the hole

and rebuild the focusser assy, then refit it.

Andrew Johansen Melbourne Australia

[MrJones]

Gday Asbytec

Yep.

The mirror and sled is simply fitted and pushed back

The focusser assy ( with rod fully extended ) is then just

poked through the large hole in the casting as far as you can

with the threaded rod on the side of the hole.

There should be enough lateral movement then to fit the

focusser over the pin on the sled and centre it then do up the three screws.

If that proves impossible, then just fully unscrew the inner threaded rod

from the brass bearing. Use some tweezers etc to fit it to the sled then pull it back through the hole

and rebuild the focusser assy, then refit it.

Andrew Johansen Melbourne Australia

This is what I remember doing with mine. I forget how exactly I got the focuser rod to go over the pin but that's what I did.

[vidrazor]

actually, have a squizz at

http://karmalimbo.com/aro/mods/ota.htm

Yours wont be identical, but it shows how 99% of Meade focussers fit

Well, looking at this image, I will assume we can indeed just key the brass rod through the rear. However those larger Meades have relative "flat" backs, whereas this unit has these indentations. I'm going to hope they will not space the pin too far up to make it difficult to see how to key the focuser on.

[OzAndrewJ]

Gday Vidrazor

Just remove the black collar and fully rebuild the focusser mechanism and try.

Having the corrector off means you can easily position the mirror anywhere you want.

There is no way Meade will have made these in a way you have to disassemble and reassemble

a std focusser assy in order to fit it. That costs money

Maybe rotate the mirror a bit to get a better angle when trying to fit over the pin.

 

Andrew Johansen Melbourne Australia

[vidrazor]

Gday Vidrazor

Just remove the black collar and fully rebuild the focusser mechanism and try.

Having the corrector off means you can easily position the mirror anywhere you want.

There is no way Meade will have made these in a way you have to disassemble and reassemble

a std focusser assy in order to fit it. That costs money

Actually, the simplest approach would have been to allow removal of the entire rear assembly. That would've made everything dead simple, and we would've never needed to remove/disturb the front optics.

 

However I read elsewhere online that Meade EPOXIED both the front and rear covers on! What on earth were they thinking? We couldn't figure out why, after removing all the screws, we couldn't remove that rear end cover, even when we were hitting it with a hammer and tap! The only way to remove them is to put the tube into a high temperature oven and bake it off! Whiskey Tango Foxtrot?

 

I mean, really? 

 

[OzAndrewJ]

Gday vidrazor

My understanding is the cells were glued in a jig to ensure

the optics atayed within a range where they could be

installed and adjusted without needing to do any figuring.

That said, i have not heard of anyone having the problems you are

so my guess is its just finding the right angle.

And if worse comes to worse, just fully remove the threaded rod

Push the sled forwards and then using needle nose pliers etc

just fit it on the stub and then pull it back out, and reassemble.

Its not that difficult.

Andrew Johansen Melbourne Australia

[Asbytec]

Actually, the simplest approach would have been to allow removal of the entire rear assembly.

However I read elsewhere online that Meade EPOXIED both the front and rear covers on! What on earth were they thinking?

I've never done a focuser swap, but learned a lot in this thread thanks to you and Andrew. I seems simple enough to reinstall without removing the ends (except to retrieve it from inside the tube in your case).

Just guessing, but due to the delicate alignments of an aplanic system, maybe it makes sense to design it so it cannot be easily dismantled. If course, that didn't make it easy on you.

Anyway, I'm glad someone knowledgeable chimed in. We both learned something, surely.

Edited by Asbytec, 27 April 2025 - 11:10 PM.