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The How to Thread

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#26 Bignorrs

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Posted 27 February 2023 - 08:24 AM

Good afternoon all,

 

I've just bought a 1990 Meade Lx5 2080, what I'm hoping for is some advice on what seems to be a lazy RA drive, it turns for a couple of seconds then stops till you give it a nudge, I checked my 12v battery and it is full. 

 

Also, previous owners have replaced the original control panel with one if their own, which is basic to say the least, it has drive speed and east/west controls, no provision for the original handset, which I would like to reinstate. Hoping someone can give me some advice on how to go about these issues. 

 

Thanks in advance from Scotland 🏴󠁧󠁢󠁳󠁣󠁴󠁿. 

 

Norrie. 

 



#27 clamchip

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Posted 03 March 2023 - 12:57 AM

If you have a focuser with this style shaft bearings you can tighten up the gear lash.

After 50 years or so you may just need grease to tighten things up.

If you still have lost motion due to too much clearance I found this works.

Measure the focuser shaft. In this example, a Criterion focuser, shaft measures 0.157" inch

and that happens to be a #22 drill bit, the closer the better on this, and I'm hoping you get

as lucky as I did. If not there's fractional drills, letter drills, number drills, metric drills, and

also reamers. Actually a hand reamer would be the best choice but a drill bit does a fine

job.

Now you lay the drill in the bearings, hold a brass or aluminum block on top of the bit and apply light

pressure. Spin the bit with your fingers. Check your work by assembling the dry parts (no lube)

and go until its zero lash, leave a little room for grease. 

Take your time, be careful not to go too far. 

Robert

 

IMG_1276.jpg

IMG_1278.jpg

IMG_1279.jpg


Edited by clamchip, 03 March 2023 - 01:06 AM.

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#28 mdowns

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Posted 25 March 2023 - 01:27 PM

Rferrante's Meade LX5 and LX 200 schematics.  Thanks Rob!



#29 mdowns

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Posted 25 March 2023 - 01:54 PM

Cross hair installation by clamchip. Thanks Robert!



#30 mdowns

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Posted 14 June 2023 - 06:43 AM

Crown and Flint orientation by Kasmos


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#31 Kasmos

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Posted 14 June 2023 - 12:08 PM

Crown and Flint orientation by Kasmos

For the record it's actually Badbacks art and to keep it simple I cropped out all of the wrong ways they can be positioned.


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#32 deSitter

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Posted 14 June 2023 - 12:18 PM

For the record it's actually Badbacks art and to keep it simple I cropped out all of the wrong ways they can be positioned.

Sometimes it is hard to tell which side is steeper, particularly long f/l 60mm lenses. I hold up the convex lens so that I can see the reflections of a light, and look at the right-side up reflection, which is coming from front surface. There is an upside-down reflection from the back surface - which should be ignored. Flip the lens and check again. Now the roles of front and back are reversed. So you compare the two front-side up reflections as you flip it back and forth, and the steeper side is the one with the smaller reflections. That goes toward the flint.

 

-drl


Edited by deSitter, 14 June 2023 - 12:19 PM.

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#33 clamchip

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Posted 02 July 2023 - 02:51 PM

Edmund 6 inch and others with a single stalk.

Something I'd like to mention,

"Avoid the temptation to bend the diagonal stalk."

Make sure the stalk is straight. You can straighten the stalk in a vise as I show in this photo.

When checking the straightness lay the stalk on a flat surface and look at the light between

the stalk and the flat surface.

The 45 degree platform is rarely bent, the brass is pretty hard.

Once the stalk is straight check to see if the primary cell is centered in the diagonal. If not

the problem is usually the focuser is not square with the telescope tube. It may be the focuser

mounting feet are not square to the focuser, or the tube is bent which is the case with my

scope here. I placed a shim on the low side for the moment just to confirm my findings. At

some time the focuser got clobbered from the sky side denting the tube where the focuser

mounts.

Robert

 

post-50896-0-02480600-1600631469_thumb.jpg

post-50896-0-10769300-1600631489_thumb.jpg

post-50896-0-84605800-1600639790_thumb.jpg


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#34 sdedalus83

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Posted 04 July 2023 - 10:01 AM

Sometimes it is hard to tell which side is steeper, particularly long f/l 60mm lenses. I hold up the convex lens so that I can see the reflections of a light, and look at the right-side up reflection, which is coming from front surface. There is an upside-down reflection from the back surface - which should be ignored. Flip the lens and check again. Now the roles of front and back are reversed. So you compare the two front-side up reflections as you flip it back and forth, and the steeper side is the one with the smaller reflections. That goes toward the flint.

 

-drl

Another way, at least with older lenses, is to check for the AR coating. Most of them are only coated on the first or first and fourth surfaces.



#35 deSitter

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Posted 29 July 2023 - 10:53 AM

Could someone how-to me on the tripod chain of the 6335/6339/6339-a? I need a close-up of the links and the hub, and if possiible a length measurement of the spokes minus the central hub and leg links. TIA

 

-drl



#36 chinacat

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Posted 12 September 2023 - 04:35 PM

I made some a few days ago for the swift 831 you sold me.

Nurse Mendy made some milk jug washers for my Jaegers 1 inch mount.

She sure knows her way around a #11 Exacto blade.

In the early days Edmund used leather washers, and these leather thrust washers

have the oh so perfect rotational friction.

Milk jug washers are really nice too. Good job Mendy.

Don't be shy about using Super Glue to mend things, Mendy glued this broken

C8 finder bracket, its as good as new. Use Loctite brand.

Robert

 

attachicon.gif post-50896-0-35224500-1492621226_thumb.jpg

attachicon.gif post-50896-0-50734700-1494711362.jpg


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#37 Senex Bibax

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Posted 15 September 2023 - 08:48 AM

I tried searching the Classic Telescopes forum for instructions for disassembling, cleaning and reassembling the old collimatable refractor lens cells with three pairs of screws (RAO), but couldn't find anything.

 

My Sears 6339A has what looks like the beginnings of fungus on the interior surfaces of the objective lenses, and I want to split the lenses and clean them. Can anyone please help? I don't want to make mistakes with this fine scope.

 

Thanks



#38 deSitter

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Posted 15 September 2023 - 09:19 AM

Disassembly - unscrew the dew shield, then unscrew the entire objective from the tube. One of each of the three pairs connects the outer to the inner cell assembly. With the pair at 12 o'clock, it's the one on the right. With the assembly on a table, remove those 3 and lift out the outer cell assembly. Do not disturb the other screw as that determines the collimation. It's no big deal to redo the collimation but why make work? The pairs are the classic push-pull arrangement for refractors.

 

With the outer cell out, you can see the retaining ring on the eyepiece side of the objective. If you don't have an optical wrench, you can usually remove this ring with a jeweler's screwdriver by applying a sideways force with the blade inserted into one of the notches in the ring. This is the hardest part - if it doesn't want to budge, don't force it! Instead invest in an optical wrench made for this purpose.

 

Once the ring is out, set up a t.p. cardboard spool vertically and lower the lens assembly SLOWLY onto the spool, so that the cell leaves the lens stack behind balanced on the spool. Again do not force it - it is very easy to wedge the concave flint element in the cell which can lead to clam chips (it is very brittle glass).

 

-drl


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#39 deSitter

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Posted 15 September 2023 - 09:21 AM

Remember the lens stack is air-spaced - they are not cemented together. Once out of the cell they can break independently of each other :)

 

-drl


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#40 Senex Bibax

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Posted 15 September 2023 - 11:15 AM

Disassembly - unscrew the dew shield, then unscrew the entire objective from the tube. One of each of the three pairs connects the outer to the inner cell assembly. With the pair at 12 o'clock, it's the one on the right. With the assembly on a table, remove those 3 and lift out the outer cell assembly. Do not disturb the other screw as that determines the collimation. It's no big deal to redo the collimation but why make work? The pairs are the classic push-pull arrangement for refractors.

 

With the outer cell out, you can see the retaining ring on the eyepiece side of the objective. If you don't have an optical wrench, you can usually remove this ring with a jeweler's screwdriver by applying a sideways force with the blade inserted into one of the notches in the ring. This is the hardest part - if it doesn't want to budge, don't force it! Instead invest in an optical wrench made for this purpose.

 

Once the ring is out, set up a t.p. cardboard spool vertically and lower the lens assembly SLOWLY onto the spool, so that the cell leaves the lens stack behind balanced on the spool. Again do not force it - it is very easy to wedge the concave flint element in the cell which can lead to clam chips (it is very brittle glass).

 

-drl

Thank you!


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#41 Senex Bibax

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Posted 17 September 2023 - 10:46 AM

Thanks again! These instructions were spot on. The only difficulty I encountered was that i had to open my optical spanner to its absolute limit to fit in the retaining ring.

 

Disassembly - unscrew the dew shield, then unscrew the entire objective from the tube. One of each of the three pairs connects the outer to the inner cell assembly. With the pair at 12 o'clock, it's the one on the right. With the assembly on a table, remove those 3 and lift out the outer cell assembly. Do not disturb the other screw as that determines the collimation. It's no big deal to redo the collimation but why make work? The pairs are the classic push-pull arrangement for refractors.

 

With the outer cell out, you can see the retaining ring on the eyepiece side of the objective. If you don't have an optical wrench, you can usually remove this ring with a jeweler's screwdriver by applying a sideways force with the blade inserted into one of the notches in the ring. This is the hardest part - if it doesn't want to budge, don't force it! Instead invest in an optical wrench made for this purpose.

 

Once the ring is out, set up a t.p. cardboard spool vertically and lower the lens assembly SLOWLY onto the spool, so that the cell leaves the lens stack behind balanced on the spool. Again do not force it - it is very easy to wedge the concave flint element in the cell which can lead to clam chips (it is very brittle glass).

 

-drl


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#42 deSitter

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Posted 17 September 2023 - 10:54 AM

Thanks again! These instructions were spot on. The only difficulty I encountered was that i had to open my optical spanner to its absolute limit to fit in the retaining ring.

Most welcome! It's always gratifying to rely on experience to help someone out. When I first cleaned a classic that needed it, I was as nervous as a March hare. I've now done it enough times that I have to remind myself not to become complacent. Always treat the concave flint element like a holy relic. Is it SO easy to get that wedged into the cell and a major headache to get it out undamaged.

 

-drl



#43 apfever

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Posted 17 September 2023 - 12:15 PM

Could someone how-to me on the tripod chain of the 6335/6339/6339-a? I need a close-up of the links and the hub, and if possiible a length measurement of the spokes minus the central hub and leg links. TIA

 

-drl

Did you already get this? I have this original style Hobby #4 chain. I'll send you some, enough for all three lengths but the original suspension design stinks. I believe the original design has one chain go from the leg to a center ring or common center. A better design is to go from each leg to the one next to it, leg to leg instead of leg to center. This won't affect the tray since the tray gets it's own spreader arms. 

 

Go to entry #19 on This LINK.


Edited by apfever, 17 September 2023 - 12:20 PM.


#44 deSitter

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Posted 17 September 2023 - 01:16 PM

Did you already get this? I have this original style Hobby #4 chain. I'll send you some, enough for all three lengths but the original suspension design stinks. I believe the original design has one chain go from the leg to a center ring or common center. A better design is to go from each leg to the one next to it, leg to leg instead of leg to center. This won't affect the tray since the tray gets it's own spreader arms. 

 

Go to entry #19 on This LINK.

I got some s.s. chain to make one. It's just for completeness, the chain serves no purpose I can see. I will try to make one I can install under tension after the tray is fixed in place. Thanks for the offer. BTW my mount came close to disaster on the first light. I had waxed the legs with some Minwax and they look sharp, but while setting up, one gave way because it was slick, and the telescope lurched at me when the strut collapsed. Chain wouldn't help there. Again a better idea would be to have holes in the outer struts and a pin that can be inserted to prevent such a collapse. At this point I've been dealing with this type of mount so long I've thought of half a dozen ways to redesign it :) But I won't do any of them. Anhistorical!

 

-drl



#45 clamchip

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Posted 19 September 2023 - 07:21 PM

If you find yourself needing to remove sticky damping grease from a mount or focuser

paint thinner works great without harm to the finish.

I have a altazimuth mount that was stored in a hot attic and the damping grease liquefied

from the heat and leaked out of the joints, dried up, and is just an awful cleanup.

A dark couple hours but just think how long it would take to build a mount like this from

scratch.

 

Robert


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#46 clamchip

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Posted 19 September 2023 - 07:42 PM

Tobacco tar on our telescopes seems to be a common problem.

Windex does a great job removing it.

Robert 

 

post-50896-0-82695900-1603644470.jpg

post-50896-0-69013500-1603644413.jpg


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#47 Senex Bibax

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Posted 03 October 2023 - 08:40 AM

Here's a really simple homemade 1.25" adapter for older RAO telescopes (Sears 6339A, in my case). I found a barrel / extension tube part / thingy from Antares in my spare parts box, with an inside diameter of 1.25". By a happy coincidence, the draw tube on the RAO focuser is very close to 1.25" in outside diameter. I simply warmed the tube in some hot water, then pushed it over the end of the draw tube. It cooled to a snug, solid fit.

 

It looks like it belongs on the draw tube, and the other end of the tube has a thumbscrew for holding the 1.25" star diagonal securely.

 

Adapter1
Adapter3

Edited by Senex Bibax, 03 October 2023 - 08:40 AM.

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#48 btyler

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Posted 18 October 2023 - 04:00 AM

B and l Criterion 8000, 8" gear grinding forks leaning repair.
I purchased the scope and have found no diagrams, service manuals ect. Everyone says it's easy or they don't break a lot. Well its 40+ years old and needs tlc. Tracking is not very good. When you engage the r.a lock the forks ans scope stand up instead of lean. There is a gap between the fork assembly and base. I have been able to look atvthe very dry bearing in the center.I will be taking pics as I go along. It could be a bearing issue, a ra gear issue too as well as the brake pads? Talked with the guy at astropix may also be in need of an adjustment for the motors to gear meshing. With all that off my chest. Any help, insight, diagrams, breakdowns would be helpful.

#49 Exnihilo

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Posted 18 December 2023 - 11:03 PM

drl suggested putting this link up as a potential source of thumbscrews/set screws etc:

 

https://us.misumi-ec...00/M3301040000/


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#50 mdowns

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Posted 22 December 2023 - 08:46 AM

Kasmos pointers on finding any image you've posted,see here.


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