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hargy
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Reged: 01/09/14

Loc: Lawrenceville, GA
LX200R secondary mirror
      #6380179 - 02/16/14 10:19 PM

I was wondering how I could make sure my secondary mirror is centered perfectly for collimation. I have used the Ho-Tech laser collimator however, on the mirror that I place where the eyepiece goes, the 3 dots are not centered. Is there some sort of adjustment I can do to correct this?

Edited by hargy (02/16/14 10:46 PM)


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hargy
super member


Reged: 01/09/14

Loc: Lawrenceville, GA
Re: LX200R secondary mirror new [Re: hargy]
      #6380224 - 02/16/14 10:49 PM

Here's another question. If i remove the front lens to look at the secondary mirror and I put it back in the same place (screw holes) will that alter the optics in any way?

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nitegeezer
scholastic sledgehammer
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Reged: 11/27/07

Re: LX200R secondary mirror new [Re: hargy]
      #6380378 - 02/17/14 01:21 AM

Before you remove the corrector plate and take a chance of doing some serious damage, are you sure you have a collimation problem? Have you done a star test?

Since the secondary mirror is not flat, I would not expect a clean reflection with a laser. The fact that you are getting any reflection at all tells me that it is not too bad, and probably better than you could achieve by taking the corrector off and making a manual adjustment.


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SteveRosenow
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Reged: 07/10/12

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Re: LX200R secondary mirror new [Re: nitegeezer]
      #6380467 - 02/17/14 03:38 AM

I just went through this on my LX6. I'll add to what Nitegeezer said.

First, DO NOT remove the corrector under ANY circumstance unless you have it marked for position and rotation. You risk nearly irreparable damage to the optical train's alignment. Meade's design has the secondary, primary, and corrector plate assembly optically figured to match each other not just as a set, but also through rotational alignment.

You need to conduct a star test before doing ANY sort of work.

Best method is to select Polaris, or this can be done in the daylight using sunlight reflecting off of a distant object such as a car bumper or power line insulator. My method is a steel ball bearing positioned on a fence post about 50 feet away.

You need to de-focus the pinpoint of light to where you have a "donut" of light about 1/8th the field of view, and determine the collimation adjustments that way.


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Pcolon1
member


Reged: 02/10/13

Re: LX200R secondary mirror new [Re: SteveRosenow]
      #6380477 - 02/17/14 04:00 AM

Quote:

I was wondering how I could make sure my secondary mirror is centered perfectly for collimation. I have used the Ho-Tech laser collimator however, on the mirror that I place where the eyepiece goes, the 3 dots are not centered. Is there some sort of adjustment I can do to correct this?

Edited by hargy (02/16/14 10:46 PM)



Because of the shape of the mirrors, there's pretty much a low chance of getting the laser to bounce in the way you are expecting. I made the same mistake on my lx90 last year when I had absolutely no idea what I was doing. Needless to say, I ended up separating the secondary mirror from the corrector plate and almost ruined the scope. Toss the laser and do a star test. Collimation on an sct last a good while so it's not needed to be done repeatedly enough to need a laser anyway.

Quote:

Here's another question. If i remove the front lens to look at the secondary mirror and I put it back in the same place (screw holes) will that alter the optics in any way?




As long as the corrector plate (what you are calling the lens), secondary, and primary mirrors are in the original position, it won't matter. The corrector plate is mated to your mirrors to reduce imperfections from manufacturing.


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hargy
super member


Reged: 01/09/14

Loc: Lawrenceville, GA
Re: LX200R secondary mirror new [Re: Pcolon1]
      #6381084 - 02/17/14 01:21 PM

I'll try it again... thanks for the responses.

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Christopher EricksonModerator
Carpal Tunnel
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Reged: 05/08/06

Loc: Waikoloa Village, Hawaii
Re: LX200R secondary mirror new [Re: hargy]
      #6381397 - 02/17/14 04:49 PM

Quote:

I was wondering how I could make sure my secondary mirror is centered perfectly for collimation. I have used the Ho-Tech laser collimator however, on the mirror that I place where the eyepiece goes, the 3 dots are not centered. Is there some sort of adjustment I can do to correct this?




WHICH Hotech laser collimator are you using?


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Markigno
sage


Reged: 01/09/10

Re: LX200R secondary mirror new [Re: hargy]
      #6381449 - 02/17/14 05:26 PM

Quote:

I was wondering how I could make sure my secondary mirror is centered perfectly for collimation. I have used the Ho-Tech laser collimator however, on the mirror that I place where the eyepiece goes, the 3 dots are not centered. Is there some sort of adjustment I can do to correct this?



Hi, when the three laser points (which at focus, they form a single point) does not fall to the center of the mirror target, then it means that the secondary mirror is not centered.
The problem of secondary mirror not centered is verifiable even with a star test. With a star out of focus if the shadow of the secondary is not centered in both intra-focal and extra-focal, then the secondary mirror is not centered.
If the secondary mirror is slightly off-center, then it is not worth correcting with removing the corrector
If the test with Hotech CT collimator with three points on the mirror target are to only 1 or 2mm away from the center target, then let it be so. Do not touch anything
Marco


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hargy
super member


Reged: 01/09/14

Loc: Lawrenceville, GA
Re: LX200R secondary mirror new [Re: Markigno]
      #6381526 - 02/17/14 06:12 PM

I am using the advanced ho-tech ct laser.
Yes. it's with the laser and it's on the mirror target. This is good to know cause if you look close it looks like a circle with points or a rounded triangle and it isn't dead center.


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Markigno
sage


Reged: 01/09/10

Re: LX200R secondary mirror new [Re: hargy]
      #6382287 - 02/18/14 07:57 AM

Quote:

looks like a circle with points or a rounded triangle



This form, like a small triangle of the laser is quite normal, because they are 3 separate laser and will probably not match perfectly in a single point. the important thing is that the center of the image formed by the three laser (either a small circle or a small triangle , that's fine too) , coincides with the center of the target drawn on the back of the mirror target , or at least just 1 or 2mm out of center.
Always remember one thing: this is still a laser (although built very well ), but the result should be " interpreted " and never taken as absolute truth. The star test is the "real " way to collimate a telescope perfectly ( whatever the optical scheme ) .
I own Hotech advanced CT laser collimator and I use it for my LX200R 12". This laser is a very powerful tool (it is almost comparable to an optical bench) , but you have to know how to use it well.
The quality of the final result also depends greatly on the focuser (or visual back ) if it is orthogonal to the primary mirror (and this never happens with a telescope SCT) . There is a special procedure to align perfectly the optical axis to the mechanical axis , using this laser . The result is surprising , but to do this it is mandatory to remove the corrector plate . This is not hard to do, but it requires good manual dexterity and precision. It should also own a focuser or visual back with the screw adjustments orthogonal. Keep in mind that a telescope SCT is very tolerant to small misalignments (I mean axial, not collimation misalignments), and these do not create problems with a good collimation on a star. But if you intend to do this work for precise alignment optical/mechanical with the laser , I can explain all the steps to follow .
Marco

Edited by Markigno (02/18/14 09:11 AM)


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hargy
super member


Reged: 01/09/14

Loc: Lawrenceville, GA
Re: LX200R secondary mirror new [Re: Markigno]
      #6385633 - 02/19/14 09:51 PM

Thanks markigno; I would appreciate it. looking forward to seeing your info.

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Markigno
sage


Reged: 01/09/10

Re: LX200R secondary mirror new [Re: hargy]
      #6387426 - 02/20/14 07:24 PM

Ok hargy, these are the basic steps to align the optical axis and the mechanical axis in an LX200 Classic, R, ACF with advanced Hotech CT laser collimator:

1) OTA pointing up, remove the screws of corrector plate and remove the great ring of plastic.
2) Mark with a pen the outer edge of the corrector plate and the telescope tube (this is the reference to reassemble the corrector plate with the right rotation). NOW you can remove the corrector plate.
3) Turn on the laser sight cross, do the procedure of co-alignment between OTA and the laser (as explained in the manual).
4) Mount the mirror target in the visual back or focuser with adjustable orthogonal
5) Check if the cross laser sight, reflected by the target mirror on the target collimator, coincides with the laser sight reflected from the primary mirror on the target collimator.
If the two reflections, are not aligned (forming a single cross), then act on the adjustment screws orthogonality of the focuser until the two reflections coincide.
Now the focuser is perfectly perpendicular to the optical axis of the primary mirror.
6) Remounting the corrector plate (matching the marks you made before removing it), put the plastic ring and the screws loosely.
7) Repeat the procedure of co-alignment between the laser and ota, center the secondary mirror (if needed) by moving the corrector plate in order to make the shadow of the secondary mirror concentric with the reflection of the primary mirror (on target collimator)
8) Tighten the screws of the corrector plate to lock it.
9) NOW you can make the whole process of collimation of the telescope with laser

In this video you can see the whole procedure explained very well. You are using a Celestron HD where you can only remove the secondary mirror. In Meade telescopes is necessary to remove all of the corrector plate, but the procedure is identical. Good luck,
Marco

Edited by Markigno (02/20/14 07:35 PM)


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hargy
super member


Reged: 01/09/14

Loc: Lawrenceville, GA
Re: LX200R secondary mirror new [Re: Markigno]
      #6389253 - 02/21/14 05:55 PM

I tried to work on it on my off days but ran out of time.. There is always next week.

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hargy
super member


Reged: 01/09/14

Loc: Lawrenceville, GA
Re: LX200R secondary mirror new [Re: hargy]
      #6436826 - 03/29/14 08:20 PM

What a project this has been. It turns out my Ho-tech laser was off. I sent it back for a new one but I think they sent me back the same one without fixing it. I cant complain about them not willing to take it back again since I let a lot of time lapse before I tried to collimate my scope due to moving and not having the time to do anything. when I had the time, one of the laser points was way off and I thought it was my scopes secondary mirror.
So after reading up on removing the corrector plate and collimating my scope. I built up enough courage to start this task. I was able to clean the inside of the corrector plate and check for slop in the primary mirror and. after cleaning the corrector plate ( I recommend not using lint free cotton pads due to the lint issue when dry) I let it air dry and it looked brand new again. I put it back together and was able to see the error I had prior. The corrector plate slipped down a bit over the years. I secured it in place and bolted it down. the cone was spot on dead center. I calculated the error from the laser and adjusted the error. When I took it out for a final star test, I was shocked at how much more detail I was able to see in Orion's Nebula. The star test was just a tad off and I started to fiddle with the knobs and knocked it out again. The good news is now I know my mistakes. When I have time, I will do a better job at collimating the scope. I do have a question for you pros. 2 out of the 3 screws are fairly snug but the 3rd feels loose. Is this normal or should all three be snug?


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nitegeezer
scholastic sledgehammer
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Reged: 11/27/07

Re: LX200R secondary mirror new [Re: hargy]
      #6436864 - 03/29/14 08:49 PM

Having one loose sounds kind of strange. When I adjust mine, I keep the screws fairly snug, to the point that I have to loosen screws before I can tighten one. When I get done, I try to tighten all just the same amount to hold the secondary firmly in place and it stays in place well unless I take it on a field trip down a bumpy road.

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Christopher EricksonModerator
Carpal Tunnel
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Reged: 05/08/06

Loc: Waikoloa Village, Hawaii
Re: LX200R secondary mirror new [Re: hargy]
      #6436899 - 03/29/14 09:18 PM

Quote:

What a project this has been. It turns out my Ho-tech laser was off. I sent it back for a new one but I think they sent me back the same one without fixing it. I cant complain about them not willing to take it back again since I let a lot of time lapse before I tried to collimate my scope due to moving and not having the time to do anything. when I had the time, one of the laser points was way off and I thought it was my scopes secondary mirror.
So after reading up on removing the corrector plate and collimating my scope. I built up enough courage to start this task. I was able to clean the inside of the corrector plate and check for slop in the primary mirror and. after cleaning the corrector plate ( I recommend not using lint free cotton pads due to the lint issue when dry) I let it air dry and it looked brand new again. I put it back together and was able to see the error I had prior. The corrector plate slipped down a bit over the years. I secured it in place and bolted it down. the cone was spot on dead center. I calculated the error from the laser and adjusted the error. When I took it out for a final star test, I was shocked at how much more detail I was able to see in Orion's Nebula. The star test was just a tad off and I started to fiddle with the knobs and knocked it out again. The good news is now I know my mistakes. When I have time, I will do a better job at collimating the scope. I do have a question for you pros. 2 out of the 3 screws are fairly snug but the 3rd feels loose. Is this normal or should all three be snug?




It is my understanding that David Ho is rather fanatical about his collimators working perfectly and that he personally checks out and collimates any unit sent back for any reason.

Is it possible that there is something else going on with your scope that might make it appear that the collimator is off?

As for the third collimation screw not being as tight as the others, That doesn't sound right and something else could be going on. Of course don't overtighten any of the three screws.

If you have a camera service center in your area, that might be a good place to find someone who can inspect your scope for subtle problems.


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hargy
super member


Reged: 01/09/14

Loc: Lawrenceville, GA
Re: LX200R secondary mirror new [Re: Christopher Erickson]
      #6438144 - 03/30/14 05:34 PM

David Ho may be fanatical about his collimators but mine is off a couple of mm. I taped a piece of paper over my lens cap and marked where the three dots are. I rotated the paper and only 2 point of light match up. 1 point of light is off. I also checked with a ruler and the laser should point .5 mm of the right. Like I mentioned before, I let a lot of time lapse and I feel I can not call and complain about this issue. I will contact him and see if there is a way I can collimate the laser myself and resolve my own error.

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Christopher EricksonModerator
Carpal Tunnel
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Reged: 05/08/06

Loc: Waikoloa Village, Hawaii
Re: LX200R secondary mirror new [Re: hargy]
      #6438172 - 03/30/14 05:50 PM

I'll bet that he will want to make it right for you more than he would worry about warranty status.

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hargy
super member


Reged: 01/09/14

Loc: Lawrenceville, GA
Re: LX200R secondary mirror new [Re: Christopher Erickson]
      #6438586 - 03/30/14 10:33 PM

I sent him an email and asked how to adjust it. I did not ask to repair or place the unit. I will let you know what happens when it does. I will admit after watching his new video, it sure make more sense to do a complete collimation and easier to follow along.

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hargy
super member


Reged: 01/09/14

Loc: Lawrenceville, GA
Re: LX200R secondary mirror new [Re: hargy]
      #6439860 - 03/31/14 05:30 PM

I sent out an email last night and it was answered within a couple of hours. Now either David Ho is reading this or someone told him about it. He personally responded to the email and will take care of it for me without a second thought. Now that is how all customer service should be like. I am very impressed with fast response to fix this.
+1 for David Ho and Ho-tech company !!!


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