meade LX200GPS Corrector plate & Secondary help needed.

[Angeleyes]

Hello

I hope someone out there can advise me on the following issue.

I believe the corrector plate and secondary mirror on my 10" lx200gps had been removed and put back wrong in the past.I purchased the scope second hand about 2 yrs ago and all seemed fine but after reading about cleaning the corrector i decided to have a look.

when i removed the thin outer plastic ring,the white painted marks on the body of the scope and on the corrector did NOT line up.the body mark was at lets say 20 past and the corrector was at half past(if as looking at a clock face).

Also i noticed that the secondary mirror holder was loose and able to turn and wiggle around within the corrector.

Well i cleaned the corrector,tightened the secondary,put the corrector back but with the painted marks lined up,collimated the scope on a small pinhole light(more that lightly not perfect) and that was that.I thought nothing more of it.

But now,a year on i am ordering bobs knobs and flocking paper,thinking of doing these mods and so reading up on how to do it when i find info telling me that if you are going to remove the secondary,you must mark its position,well my one was floating about when i purchased the scope and so was never marked.

Can i correct this myself with a star test and collimation or is there more to it.

Over to you

Regards

Tim

[barkis]

Firstly, The fitting of Bobs Knobs does not require the removal of the secondary, but I'm sure you know that already. Also, it cannot be removed completely without removing the plate, or there is a risk of it falling out and impacting the main mirror.

I would fit the B/Knobs and do a collimation including a star test.

If it is OK then job done. If it is not satisfactory, then withought touching the secondary again, proceed to realign the corrector according to the marks that are there. Make sure you do not over tighten the plate fixing screws. Tight is tight, too tight is distortion.

Make sure the plate is clean before you put it back, you don't want to see finger marks on the inside, after you have re fitted it.

Clean it gently with tepid water only, no polishes of any kind, and use gentle strokes with a lint free cloth.

You can get advice here too.

http://www.meade4m.com/

Ron.

By the way, I have Meade LX90, and my secondary has been rotated without any adverse effects. It too must not be overtight though.

[Angeleyes]

Thanks Ron

I did align the white marks up on the corrector a year ago,i do not understand why they were off set in the first place,i am sure it never came from meade like that.

What i am really at a loss with is any problems that may occur from the removal and re fitting of the secondary mirror as i am sure this has been done by the last owner incorrectly.

I do know i don't have to remove anything to fit bobs knobs but as i will be removing the corrector pate to flock the tube i may as well address any and all other potential problems with the optics while i am there.

This scope has failed to deliver what i call good,clean crisp images both visual and for imaging since i have owned it.In fact i had a lx5 8" beside the lx200 and the old lx5 with worn coatings on the corrector made the lx200 look stupid for both visual and imaging.

I thought at the time the lx200 just needed collimating but this is all before i found the above problems.I hope to finally correct all this and get from the scope what it is really capable of.

Thanks for your reply and help,other ideas or opinions are welcome before i pull it all apart.

Regards

Tim

[barkis]

Is the corrector profiled Tim. You know, shaped as to modify the incoming light, and not just a plain uniform disc of glass, and is it coated as with Mag. Fluoride giving that Bluish tinge that always looks so nice.?

I would hope it is the genuine plate for the scope, and not a facsimile.

Can't believe anyone would do such a thing.

Did you know who you bought it from? I don't want to sound too negative here, but all possibilities have to be considered.

Correctly aligned and collimated, it should give flawless performance.

Meade's engineering hasn't been perfect in the past, but their optics can't be questioned.

You could perhaps write or email Telescope House, they may be able to help you, I'm sure they repair/ refurbish Meade SCT's.

That's if something of that nature is required.

You must be pretty downhearted about this, and understandably so.

Hope you get it sorted mate.

Ron.

[barkis]

Just a note on the secondary mirror. As far as I'm aware, the optics are all Spherical surfaces, and to make that work, and correct the incoming starlight, is the corrector plate.

I don't think the secondary would require any special orientation, merely that it should be capable of proper adjustment during collimation. I don't have to stress to you the importance of collimation being less than perfect for best performance. Also, cooling of the scope is a paramount requirement too.

I've proved that to myself using mine.

Simply putting the scope into action on a Saturn observation almost immediately after sliding back the Roll Off Roof of the Obs. showed a terrible image. Could not get a decent focus at all.

This was an early evening attempt, and I thought the Observatory was freezing. However, an hour or more later, when I went and retried, a different result altogether, the planet looked infinitely better, and as the evening wore on, became perfect, and a joy to behold.

I'm not attempting to mislead you, I know you are quite aware of what I'm saying, merely how important the two aspect of collimation, and instrument cooling, are essential to the telescopes performance..

Sorry for the long sermon Tim, I can't seem to use just a few words, I seem to have to write a story..

Ron.

[Angeleyes]

Funny you mention the facsimile plate,i have read that some scopes in the past have had a broken plate and some fool thinks they can have one cut at a glass shop.

Fortunately for me,my plate is the real deal with uhtc coatings and all in good condition---thank god.

over the past year i have left the scope for over 2 hours before trying it,nope no good.

I do know the scope was one of the last gps models made before the change to to the "R" and that meade had many problems with them at that time regarding quality control including the "R" model with many complaints but apart from this issue my scope and mount have performed perfect.

I have wondered if the corrector had ever been replaced for one from another scope,no way to tell that i know off.

Anyway i will give it a dose of bobs knobs,flock the tube and under the stars i will ramp up the mag and collimate it. if that don't work then i will have to send it to telescope house and wear a large bill,or sell it and buy a tasco lol

Regards

Tim

[barkis]

Well, good luck mate. It still might come good for you.

Ron.

[RobH]

Hello Tim, I agree with Ron, the secondary doesn't need to be oriented in any particular way....it's only the corrector that needs that.

I bought a S/H 10 inch LX200 a few years ago, and got it home to find that the DEC drive would slew, but not track properly.

I sent it to TH and thay very quickly sorted the whole thing for me...I can thoroughly recommend them.

BTW....I like your Avatar.....Khaaaaan!!!

Cheers

Rob

[Angeleyes]

lol Rob

The Avatar remind me of me in the dark trying to find that dso on a cam chip lol.

If my work on the scope don't give me the results i am looking for then i will book it in at TH.

I will save a few pound by dropping the scope to them instead of posting it(big letterbox needed) but at the moment as you know the pounds are a bit tight here lol so it will have to wait a while.

I hope after a spot on collimation the scope performs,i also hope flocking the tube and painting the baffles with blackboard paint will help.i am going to get the flocking from Edmund Optics (hope this is good stuff) and bobs knobs from the US.

I don't fancy dropping tools on the corrector in the dark and making things worse

Anyway i will have a go at it as they say and see what happens.

I need it done as i have peltier cooled the dsi colour and i want to try it but the scope needs to be right.

I will let you all know the result of all this but for now stand well back because Meade parts are about to fly everywhere

Regards

Tim

[alfingido]

What about a phone call to TH to discuss your problems? They may say," oh, we get loads like that, you just need to......." well, you get the picture.

I had a 10 LX200gps last year, it was really nice and sharp, it would be a shame not to get it sorted properly as I am sure you will be very pleased with it when its working right. Or, you could drop it off to me, not that far from TH myself, and I will look after it for you

Allan

[wlacy004]

Just a note on secondary alignment with the OTA in a 8" Meade LX200 GPS.

My secondary was also loose on the corrector plate.

I had heard that the secondary should be aligned with the rest of the optics, however I have also heard the opposite.

When I removed the corrector plate from the OTA in order to tighten the secondary mount I noticed rust around the Bob's knobs I had installed.

Having nothing to loose as the secondary had already been rotated, I set the secondary on some clean tissue (Kleenex type as per Meade cleaning directions) and removed the Bob's knobs.

This released the secondary from the cell.  I lifted the secondary cell body and the secondary was left behind.

The secondary is mounted on an aluminum mount.  This mount had a mark (black marker) which was aligned with the small screw on the plate where the Bob's knobs are located.

Having no other instructions, I aligned the mark with the screw and aligned this with the alignment mark on the outer edge of the corrector plate.

After putting everything back together and collimating, my optics look just as good as the first time I used it.

The secondary, having a factory mark, tells me that the secondary should be aligned in a particular fashion.

The quality of the view, and the ability to quickly collimate confirms this.

Also, be careful not to loose the small washers inside the secondary body.  They are aligned with the hole in the aluminum secondary mount and the protrusion on the

secondary adjustment plate.