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LX200R 10" vs C-11 Part 2

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#1 JerryWise

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Posted 05 July 2006 - 08:33 AM

Hope no one minds my starting a second thread on this. The original thread is getting a bit clunky with the number of images.

To summarize, the C-11 is out resolving the LX200R. The LX200R had a problem. When collimated outside focus and then moved to inside focus it no longer is in collimation. This would make it out of collimation at focus. The LX200R 10" is now at Meade for repairs.

We are attempting to diagnos the problem with photos of the baffle tube and mirror assembly clearance.

The collimation problem is best shown in this photo:

Attached Thumbnails

  • 1030066-Focus Collimation Composite.jpg


#2 JerryWise

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Posted 05 July 2006 - 08:33 AM

Members have posted excellent images of thier LX200R 10" mirror assembly to baffle tube clearance. There seems to be excess clearance.

For comparison the following are similar images of, first, a Meade 14" LX200 UHTC mirror to baffle tube fit. The tube was flipped over so one image is of the left side, the other the right. Compare to these images of the LX200R.

Attached Thumbnails

  • 1030067-LX200 14.JPG


#3 JerryWise

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Posted 05 July 2006 - 08:33 AM

This image is the mirror baffle tube fit from a new Celestron C-11 XLT. One image is of the left side, the other the right.

Attached Thumbnails

  • 1030068-C11 Focus.JPG


#4 LLEEGE

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Posted 05 July 2006 - 09:08 AM

:question:

#5 JerryWise

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Posted 05 July 2006 - 09:17 AM


Yes Luke, me too. I can't draw a conclusion from the images of baffle tube fit. I was hoping someone could shed some light on it.

Looks like the LX200 14", and Celestron C-11 have a little tolerance on the fit. Not as much as the LX200R. I have to go back to the mirror moving in a non-perpendicular path for collimation moving out. The baffle tube fit seems as if it would show as mirror flop. OTAs with mirror flop (every SCT OTA I've worked with) holds collimation fine. My old 10" LX200 had so much mirror flop you could put a grass skirt on it and be entertained. But it held collimation no matter how that mirror was situated. Maybe the truth will be known when mine gets back from Meade.

#6 LLEEGE

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Posted 05 July 2006 - 12:38 PM

Their fix should be an interesting one. I wonder.......
How is 10Penny doing?

#7 steddyman

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Posted 05 July 2006 - 01:56 PM

My old 10" LX200 had so much mirror flop you could put a grass skirt on it and be entertained. But it held collimation no matter how that mirror was situated.


Thanks for that rather graphical explanation Jerry. I'm very new to this so didn't realize that mirror flop could not affect collimation.

Your photos look like there is much less tolerance than my LX200R.

I wonder if its possible for the outside diameter of the baffle tube to vary?

#8 JerryWise

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Posted 05 July 2006 - 02:36 PM

Their fix should be an interesting one. I wonder.......
How is 10Penny doing?


They booted 10Penny.

But points were proven all the way around.

I am wondering if Meade will fix the collimation and, if so, will the others be recalled.

#9 inaPICle

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Posted 05 July 2006 - 02:37 PM

Just a random thought here, but given the hyperbolic nature of the secondary could this make collimation problems worse?

My thinking is that the same amount of mirror flop between a classic SCT and an R series may show up as having a much worse impact on the collimation of the R series OTAs.

My understanding of optics is that a true RC design is very sensitive to primary collimation errors due to the hyperbolic nature of both the primary and the secondary.

This will be worse still in the Meade R series because the primary is supposedly a very fast f/2 (heard through the grapevine so I may well be wrong) and the secondary is more highly aspherical than a true RC design.

So any R series flop may well show collimation errors that would not really be apparent on the classic.

If you look at all the real RC designs all of them focus by moving the secondary with the backfocus some fixed point behind the mirror, or by using a crayford if you have the backfocus to fit one in. The primary is fixed to a mirror cell that allows collimation. The RCX fits that pattern but for the fact the primary mirror cell is fixed.

This does make me wonder if for the R series Meade would have been better off using the same OTA tube as the classic but fixing the mirror cell and using a crayford on the back end instead of the moving mirror design.

#10 JerryWise

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Posted 05 July 2006 - 03:42 PM

That is an excellent point inaPICLe. My RCX was spot on. Matter fact, I never touched collimation. It first went from Meade to a dealer in the NE then to me. Collimation fine outside to inside focus. Then it went back to Meade then back to me. Same on the collimation. I could not see any reason to touch collimation so I never did. I put a FeatherTouch on this LX200R but there is not enough focus range to make it work under all circumstances.

Even with a Crayford, I would feel much better with Meade engineering providing it and blessing the system.

#11 inaPICle

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Posted 05 July 2006 - 04:24 PM

There is a problem with my idea of a fixed mirror and crayford R series when dealing with focal reducers.

Unless you have a huge amount of backfocus for normal use you will never be able to bring the optical train to focus with a reducer in place, particularly something like a Meade 0.33x reducer. If you do have the backfocus the scope will be very rear heavy in normal use.

If I've got my head round this the right way a reducer is a positive lens so the focuser would have to be cranked in to bring it to focus.

The problem is lessened with things like the AP focal reducers with are 2" in diameter and so slide inside the focuser saving a huge amount of backfocus. They seem to get used with the RCOS scopes that way and they seem to keep the mirror spacing close enough to the sweet spot.

To truely make the fixed mirror design work Meade would have had to retool a very large chunk of their accessory line, and that wasn't/isn't ever going to happen.

#12 JerryWise

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Posted 05 July 2006 - 08:04 PM


Dean posted some information on the AP reducers in another thread and I purchased one. Was trying it and it looked very good when I found the collimation problem. I agree on the Meade FRs. I have both and neither seems to work well on the RCX line.

#13 Moggi1964

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Posted 05 July 2006 - 08:27 PM

Jerry,
I plan on fitting the Peterson Eyeopener to my 10"R and wondered what the maximum focusser length might be that still allows the scope to clear the base when slewing between the forks (I'm not explaining myself very well; sorry)?

I figure if the issue you discuss is evident in my scope then I will just go for the external focusser (Feathertouch for example) with the greatest backfocus.

Hope you get your scope back soon and the problem is gone.

Morris

#14 JerryWise

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Posted 05 July 2006 - 08:32 PM

Hey Morris. I have only the OTA so I can't say for sure on the Fork clearance. On my RCX the Peterson would clear no problem.

#15 Moggi1964

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Posted 05 July 2006 - 08:58 PM

Of course! I forgot that Jerry!

Perhaps someone else can chip in here?

Morris

#16 LivingNDixie

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Posted 06 July 2006 - 10:04 AM


My old 10" LX200 had so much mirror flop you could put a grass skirt on it and be entertained. But it held collimation no matter how that mirror was situated.


Thanks for that rather graphical explanation Jerry. I'm very new to this so didn't realize that mirror flop could not affect collimation.

Your photos look like there is much less tolerance than my LX200R.

I wonder if its possible for the outside diameter of the baffle tube to vary?

My second Lx200 8in Classic had more mirror flop then the first one I had, but it had just as sharp optics and thats all that matters to me :)

#17 JerryWise

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Posted 06 July 2006 - 11:05 AM


My old 10" LX200 had so much mirror flop you could put a grass skirt on it and be entertained. But it held collimation no matter how that mirror was situated.


Thanks for that rather graphical explanation Jerry. I'm very new to this so didn't realize that mirror flop could not affect collimation.

Your photos look like there is much less tolerance than my LX200R.

I wonder if its possible for the outside diameter of the baffle tube to vary?


I'm sorry Steddyman, I missed your post. Was wrapped up in some stuff at work.

I just don't know about baffle size. It seems there was an assumption made about mechanical fitting in the production process and it wasn't correct. That's why so many are off. I haven't seen a post (that I recall) without a collimation problem on the 10" version. That should be a very popular size too.

Looks like it's wait and see how Meade handles it.

#18 michaeloconnell

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Posted 06 July 2006 - 12:54 PM

Well, I've been following the threads here and on the yahoo groups. At this stage, I've come to the conclusion that I will forgo buying the LX200R OTA and I've placed my order to buy a 12" LX200 SCT OTA instead. I just don't fancy spending my hard-earned money to be a Meade LX200R beta-tester, especially with the prices they charge over here in Europe.
The info placed here on this site and on others has been really useful and informative. Many thanks to everyone here. Just proves how great the internet really is.

Clear skies,

#19 AstroArlo

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Posted 06 July 2006 - 05:30 PM

Jerry and Steddy:

I want to commend you (and others in this thread) for an objective and systematic analysis and comparison of the scopes and the problems you encountered. I think you attempted to eliminate all of the variables except for the scopes themselves.

Also, the photos are worth a thousand words, to use a cliche. I agree with those who say you should be an official beta tester.

I would love to see you using your talents to image or observe instead of debugging your instrument - good luck in the detective work.

#20 JerryWise

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Posted 06 July 2006 - 06:51 PM


Thank you very much for your kind words Arlo. I wanted to prove out the LX200R concept and then go for the 14" LX200R version.

I think Steddy and I both would be delighted to volunteer the analysis and testing of your 20" RCOS when it arrives. I think that is the most impressive signature line I've seen. Excellent choices.

#21 Keith Myers

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Posted 06 July 2006 - 08:51 PM

Jerry, you hear any rumblings from Meade about when you should expect your scope back? What is the procedure to get status on your RGA without having to sit on the phone for hours?

Keith
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#22 JerryWise

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Posted 06 July 2006 - 10:49 PM


Haven't heard a thing. If it's like the RCX and the Ultra Wedge, it will just show up one day. A few more weeks and we will call but that long hold time is something to be avoided if possible.

#23 Moggi1964

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Posted 06 July 2006 - 11:26 PM

Jerry,
I can confirm the following issues were evident on my 'new' 10" R:

1) RA clamp not working;
2) mirror lock defective (replaced);
3) DEC drive badly binding;
4) corrector plate and secondary rotated about 8 degrees axially to primary.

..and a few other things!

I figure it should be better than 'new' when I get it; I will let you know.

Morris

#24 steddyman

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Posted 07 July 2006 - 07:32 AM

I think Steddy and I both would be delighted to volunteer the analysis and testing of your 20" RCOS when it arrives. I think that is the most impressive signature line I've seen. Excellent choices.


Yes, I will be more than happy to provide my services in testing your 20" RCOS. Let me know when you're ready for my home shipping address :)

#25 physics911

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Posted 07 July 2006 - 08:21 AM

So what do you think Meade is going to do now? I don't know if enough people have contacted them regarding this yet that they know for sure there is an issue, however, I am sure they read forums the same as the rest of us. The three possibilities as I see it are: 1) They don't officially acknowledge a problem but repair/retrofit the ota in someway that corrects the issue. 2) The problem is widespread enough they do a voluntary recall. Which I am sure is unlikely. 3) They say "You only spent $1800, you can't expect perfection".
I am finally going to have clear skies tonight and tomorrow it looks like so I will get some testing done.


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