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LX200R 10" vs C-11 Part 2

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#51 steddyman

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Posted 16 July 2006 - 06:43 AM

I managed to get out again last night under some very clear skies without the moon up.

I took a number of photos with my D70 in Prime Focus mode. These shots are of me moving the telescope through the point of focus so you can see collimation on both sides. The shots got very murky the nearer to focus I come:

Posted Image

I didn't manage to get a shot with it actually focussed, so the nearest is the blob. As you can see I didn't actually manage to collimate it properly before the taking these shots, so it is a little out on both sides.

The other thing I don't like the look of is the distrubance on one edge which I have noticed visually too. On top top row it is at the top and on the bottom row at the bottom. I can't see anything intruding in the tube so I am not sure what this could be.

The scope had been out for two hours prior to taking the shots so it should have had plenty of time to come to the right temperature.

Steddyman

#52 jrcrilly

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Posted 16 July 2006 - 07:16 AM

That disturbance looks and behaves like a typical heat plume.

To evaluate the optics you'll want to take the inside/outside shots much closer to focus and shorten the exposure time. If seeing permits, a Barlow would also help. We want to see five rings or so with a bright center spot.

#53 JerryWise

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Posted 16 July 2006 - 08:45 AM

As John says, that plume certainly looks like a classical cooling problem.

It may be just me, but it seems the CO (central obstruction) shadow is offset to the 2 oclock position outside focus and the 8 oclock position on inside focus. If that is the case, then if the outside focus were perfectly collimated would that not move the CO toward the 8 oclock position until centered on outside focus. With this done, my massive fortunes would bet the offset toward 8 oclock on inside focus would continue by the same amount. Making the scope in collimation on outside focus and further out of collimation on inside focus.

The central obstruction shadow should be offset in the same direction on outside and inside focus (see third image here). With this situation, if what I'm thinking indeed exist, this (in scientific terms) sucker won't work like it should. Same collimation deal going on. Could be wrong.

(Nice work Steddyman. Thank you.)

#54 jeffk1965

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Posted 16 July 2006 - 08:48 AM

I agree the touched up scratches do not look good and the owner should have been contacted about them first.

jeff

#55 tboss70

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Posted 16 July 2006 - 09:38 AM

"The central obstruction shadow should be offset in the same direction on outside and inside focus (see third image here)."

I've never tried this and am posting without actually thinking about it...BUT...if you were collimating with a diagonal, would that show the collimation offset on opposite sides of both intra and extra focus?

I seem to recall my C9.25 doing the same thing when I collimated with diagonal.

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#56 JerryWise

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Posted 16 July 2006 - 10:44 AM


Todd, the diagonal would flip the image but, if I'm not mistaken, the out of collimation shadow would stay on the same side from outer to inner focus.

I would run up and test it on the Celestron C-11 but I just got that one in perfect collimation and its over 100 degrees in the dome. May well be wrong. (I'm real gun-shy about making a mis-statement right now because of the implications in this Meade thing so I'm trying to be careful. I think we are safe though in assuming if collimation is perfect on one side of focus and out on the other the LX200R has a problem.)

#57 LLEEGE

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Posted 16 July 2006 - 10:49 AM

I agree with Jerry. Even if the image "flips" the collimation should not change on either side of focus.

#58 steddyman

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Posted 16 July 2006 - 10:59 AM

Thanks for the tip on the heat plume John. This disturbance always seems to be about this position every time I take the scope out. It is very hot here at night now, so it could be heat related.

Because I was using and DSLR it was very difficult to adjust the focus and exposure manually. I don't have it linked to the computer so I am relying on the tiny screen on the back. I also don't have a guide scope. You are right though, the exposure is too high on most shots hence the lack of sharpness. What I wouldnt' give for an EOS 20Da.

Also, the smaller the circle got the less fuzzy and defined it became. This was a very clear night so I don't think seeing was responsible. Stars looked like little fireballs.

I am still a baby at this, so it could well just be the effects of seeing. I didn't have a diagonal installed when taking these shots and the shadow and heat plume definately seemed to reverse when I crossed focus.

Steddyman

#59 Keith Myers

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Posted 16 July 2006 - 02:33 PM

Funny, I have a 2" long shallow scratch in the paint under the very same dovetail ( I assume MaxMount) on my LX200R 10" OTA. Must be the same person assembling or rather banging the dovetail onto the tube. Hidden by the dovetail, seen when removed and now hidden again by the Losmandy DM10 dovetail plate. Isn't Meade quality control - Grand!? NOT!

Keith

#60 Keith Myers

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Posted 16 July 2006 - 03:09 PM

I got the newly received 10" OTA back after return from the RGA at Meade. When I took off the MaxMount dovetail and noticed the scratch I began to have my doubts as to whether I properly recorded the S/N of the original OTA. I thought I received a unit 2 S/N's earlier in production from the original S/N I sent in under RGA. But after seeing that scratch which looked so familiar I have my doubts now and think maybe I got back the original OTA. Unless the person doing the assembling is very consistent with mishandling of the dovetail and scratches every OTA similarly. Anyway, I now know that the OTA does not preserve collimation in any way after being subjected to the abuses of UPS shipping from Meade. And the trip was local within 70 miles of Irvine CA. The returned OTA was badly out of collimation again looking identical to the first OTA. I spent an hour collimating it last night and things look definitely improved. I get similar collimation patterns both sides of focus now. Even better was that even though my test of imaging was hampered by blustery winds, very short exposures did give me round stars this time. Even better was that optical collimations and camera collimations were the same. So it looked like Meade either fixed my original OTA or gave me one that doesn't seem to have any problems so far other than the slight image shift when changing focus. I'll be able to better evaluate this upcoming new moon weekend from a dark sky site and the full imaging rig including Crayford focuser and use of the mirror lock.

Since the FeatherTouch Microfocuser is not an option so far for the "R" model, can anybody tell me whether the Peterson Engineering EZ-Focus modification will disturb anything with the ostensibly good performing OTA? I would like an easier focus feel but don't want to mess with anything if it will hurt my newly RGA'd OTA.

Thanks in advance,

Keith
:p

#61 tboss70

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Posted 16 July 2006 - 05:13 PM

OK, I need a tutorial...Im really not trying to hijack the thread, just need some clarification before i go on. I hope thats ok.

When viewing through a refractor w/out a diagonal, you see the image inverted. My question is this: Does the light path before focus show the image one way and after the focus point show the image another way...(inverted)?? Or vice versa.

If so, wouldn't this explain why you see the CO pulled one way on one side of focus and pulled the opposite way on the other side of focus?

#62 tboss70

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Posted 16 July 2006 - 05:16 PM

I realize im comparing apples and oranges here but Im trying to understand the light path and why collimation (if its out) should be on the same side on intra and extra focus.

My C9.25 does not show "collimation out" on the same side of intra and extra focus....does this mean I have a problem with mine too?

#63 LLEEGE

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Posted 16 July 2006 - 06:09 PM

Todd, the problem is the collimation is good (centered CO) on one side of focus and bad (off centered CO)on the other side of focus. The image flipping on either side of focus should be centered if collimation is good.

#64 Jeff Crilly

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Posted 16 July 2006 - 06:14 PM

4) corrector plate and secondary rotated about 8 degrees axially to primary.



How did you know that?

#65 Moggi1964

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Posted 16 July 2006 - 08:08 PM

I didn't but that's what Dr. Clay found and told me about.

Not entirely sure I know what it means but I figure it wasn't how it was supposed to be otherwise he wouldn't have corrected it.

What does it mean John?

#66 Joad

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Posted 16 July 2006 - 08:52 PM

I know you asked John, who knows a heck of a lot more than I do, but I'll try anyway: the corrector plate and the secondary mirror are figured to align precisely with the figuration of the primary mirror (that's why one is advised not to remove the corrector plate to clean it without taking precautions to replace it exactly as it was factory installed; it's also why you can't simply replace a broken corrector plate without having to get a new primary also). If the corrector/secondary were rotated 8° off their proper alignment, the performance of the scope would suffer.

#67 JerryWise

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Posted 16 July 2006 - 09:56 PM

.............

My C9.25 does not show "collimation out" on the same side of intra and extra focus....does this mean I have a problem with mine too?


Todd, I've been in the observatory the last two hours with a Celestron C-11 and Intes MK66 mounted side by side. I decollimated the MK66 and the off center central obstruction (CO) shadow stayed in the same place both sides of focus. Also, on the C-11 I put a wide angle EP in, moved a focused star to the edge of the field and defocused outside. You could see the central obstruction was off center. Moving to inside focus it was off center in the same direction.

In the procedure for collimation you put your hand over the end of the scope on the side the CO is offset and this will be over the screw that needs adjusting. If, when you move to the other side of focus, if the off center CO moved to the opposite side the proper screw for adjusting would also move to the opposite side. The light path would have turned itself upside down with the focusing action. The focus moves forward and backward through the focal point and the image stays in the same orientation. Also, if the central obstruction did flip side to side moving through focus, Jupiter's moons would flip side to side as you focused on it.

Diagonals can have an effect on collimating. Have you tried it with the diagonal out?

#68 Moggi1964

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Posted 17 July 2006 - 08:20 AM

I know you asked John, who knows a heck of a lot more than I do, but I'll try anyway: the corrector plate and the secondary mirror are figured to align precisely with the figuration of the primary mirror (that's why one is advised not to remove the corrector plate to clean it without taking precautions to replace it exactly as it was factory installed; it's also why you can't simply replace a broken corrector plate without having to get a new primary also). If the corrector/secondary were rotated 8° off their proper alignment, the performance of the scope would suffer.


Thanks Joad,

I get it :D

Morris

#69 physics911

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Posted 17 July 2006 - 11:53 AM

I don't mean to be the slow guy here, but I still don't understand why the corrector and primary have to be a matched set. As someone stated earlier, why aren't the corrector and primary both completely symetrical (with tolerances), about the central axis? I find it hard to believe they individually configure each set of glass or even use some other iterative method of matching corrector to primary. What am I missing?

#70 jrcrilly

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Posted 17 July 2006 - 12:02 PM

I find it hard to believe they individually configure each set of glass or even use some other iterative method of matching corrector to primary. What am I missing?


That's what they do (Celestron does the former, Meade does the latter). You'd have to ask the manufacturers their reasons.

#71 kgeakin

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Posted 19 July 2006 - 12:41 PM

The curious collimnation problem in the 10" 200R may be due to the baffle that the primary mirror rides on being installed slightly off axis at the factory. This could also explain the assymetric gap between the mirror and the baffle. This could be checked by using a secondary focuser perhaps. Just a thought.
Kim

#72 JerryWise

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Posted 19 July 2006 - 05:00 PM


Hi Kim and a warm welcome to CN. Very good observations. In an earlier thread this was explored and your thoughts are exactly in line with the hottest theory going. We are waiting now for Meade to sent the scope back (five weeks and counting). Hopefully there will be some explanation.

#73 Keith Myers

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Posted 19 July 2006 - 07:37 PM

Jerry, don't hold your breath waiting for an explanation of what was done to your scope. I got mine back and there was nothing in the box describing the service action. I called Meade Customer Service and asked what they had done to correct my tilted baffle/off-axis baffle problem that caused my 'clipped' stars and widely different collimations postions intra/extra focus and for visual vs. camera use. All I can say is that they have appeared to fix the problem. I now have same collimation position intra and extra focus and camera collimation matches visual. Its funny that I got my RGA back before you and you sent yours in before me.

Keith
:shocked:

#74 LLEEGE

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Posted 19 July 2006 - 08:26 PM

Thats good news, Keith!

#75 steddyman

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Posted 20 July 2006 - 05:20 AM

I desperately need this explanation. My scope was imported directly from the states, therefor I don't really have a warranty I can use.

I have local dealers that service the Meade scopes, but they would need to know what the problem is to fix it.

Is there anyway Meade can be pushed to provide an explanation?

Thanks
Steddyman


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