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Meade corrector plate problem

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#1 ToeMoss

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Posted 23 October 2005 - 10:45 PM

I'm trying to adjust the tilt of the secondary but when i bear down on one of the three adjustment screws, the assembly often wants to rotate as if the center screw were being turned, is there a way to lock the rotation of the assembly in place? How am I supposed to properly collimate this telescope? :confused:

#2 garyc11

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Posted 23 October 2005 - 11:06 PM

are you at the end of the travel on the adjustment screws?

#3 ToeMoss

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Posted 23 October 2005 - 11:14 PM

Hmmm...they are a little tight, but they should have some travel left in them. I'll check though. If they are at the end of their travel, do I need to back out all the adjustment screws a turn or so in order to get the proper tilt?

#4 garyc11

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Posted 23 October 2005 - 11:19 PM

you would do your collimation the same way you just back out a screw rather than tighting it.

#5 garyc11

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Posted 23 October 2005 - 11:38 PM

have you ever thought about installing bob's knobs?

#6 ToeMoss

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Posted 23 October 2005 - 11:57 PM

Yeah, the more I poke around the corrector plate with my screwdriver the more I think of it. I think I'll just order them before I do any damage.
Thanks for help.

#7 jmcdonald

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Posted 24 October 2005 - 02:20 PM

Scopestuff has knobs. I like mine.
The center screw doesn't rotate the secondary. See this

#8 jmcdonald

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Posted 24 October 2005 - 02:33 PM

I assume you mean the Meade SN8. If so, rotation is controlled by the locking ring on the front of the corrector plate. See this
link for a good description of adjusting and locking down the secondary rotation on this scope. There's lots more info on that site as well.

I've had the same issue on my SN10. Cotton gloves are a good investment when working around the corrector plate.

You may already know all of this, but if not, the center screw isn't meant to rotate the secondary (although it might if the secondary is loose anyway), it adjusts the movement of the secondary towards and away from the primary mirror. I'd leave it alone unless you believe the offset was set wrong at the factory. If you loosen it too much without tightening the other 3, the secondary holder will 'sag' and it's a pain to get it adjusted correctly again (take my word for it).

And, again, this may be old news to you: a good sight tube is pretty necessary to adjust the rotation if it's off. Most sight tubes are too long for an f/4 scope so watch out. You may want to make your own. You'll need a sight tube and cheshire at a minimum to collimate that scope.

Scopestuff.com has replacement thumb knobs for this scope. Beware when you change them out, do them one at a time and follow the instructions.

Good luck, that's a sweet scope.

#9 Guest_**DONOTDELETE**_*

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Posted 24 October 2005 - 03:36 PM

Hey tom, there is some sort of cover over where the diagonal support bolts are suppsed to be adjusted from. How did u remove that cover (with the blue centre).

BTW now that i illuminated the tube with a flash light i can see dust specks on the primary & inside the corrector plate......So i guess the secondary might have it as well.

Any suggestions on how to clean em?

mosaic...

#10 ToeMoss

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Posted 24 October 2005 - 06:56 PM

The center screw doesn't rotate the secondary. See this


Interesting piece, I had not noticed those holes in the ring. However,the center screw on my scope seems to do nothing *but* rotate the secondary mirror about the primary axis. I have not been able to loosen the screw at all, I'm thankfull since I have no wish to adjust vertical offset, I only messed with the center screw to beging with because I noticed the whole secondary rotate when I was adjusting on of the smaller screws, had to rotate back.

a good sight tube is pretty necessary to adjust the rotation if it's off. Most sight tubes are too long for an f/4 scope so watch out.


I do have a 2" Jim Fly teletube, it is designed to work with various f number scopes so I think I'm good there, I do have a problem with seeing the whole secondary in the sight tube thought, wonder if its designed to work with the large secondary on the LXD75 SN8.

#11 ToeMoss

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Posted 24 October 2005 - 07:29 PM

How did u remove that cover (with the blue centre).


It just pops off. I kinda enjoy poking around the corrector plate with sharp objects, so I use a screwdriver. Look closely for where the cover meets the rest of the assembly and *carefully* insert something like a credit card into the gap and give a little twist, it should pop right out.

dust specks on the primary & inside the corrector plate... Any suggestions on how to clean em?


Sure, get one of nice little squeezable puffer blowers, can't do any damage that way, or do what I did and get a fancy camel hair lens brush, if you brush just right, believe it or not, you can put perfect little scratches on your beautiful lenses, it's freaking great. Seriously, I tend to learn the hard way, you don't have to.

#12 jmcdonald

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Posted 25 October 2005 - 03:28 PM

I'd call Jim Fly if you have trouble seeing the entire secondary using the teletube -- he will probably have suggestions. You have to be able to see the outline of the secondary to adjust it correctly -- especially rotational adjustment.

I have a 2" Telecat and can't even insert it fully into the focuser (due to a nut on the inside of the drawtube). Maybe you have a similar problem. I would've sent it back, but I'm upgrading to a JMI focuser soon. :yay:

Sorry to hear about the scratches on your corrector plate ToeMoss. :tonofbricks:


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