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Precision Centering Adapter

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#1 Cj1319

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Posted 17 January 2013 - 10:33 PM

Hello all,
I plan on buying a laser collimator to tune up my XT8. I noticed that Orion sells a Precision Centering Adapter. Is that worth getting for collimation and/or regular eyepiece viewing?
Thanks,

#2 dpwoos

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Posted 17 January 2013 - 10:47 PM

I would get the Glatter Parallizer - a great adapter that ensures that your collimator and 1.25" eyepieces are held parallel to the optical axis.

http://www.collimato.../parallizer.htm

In fact, I would get a Glatter laser collimator as well.

#3 panhard

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Posted 17 January 2013 - 10:56 PM

for the difference in price I would get the parallizer. :grin:

#4 Cj1319

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Posted 18 January 2013 - 08:28 PM

Thanks for the responses, I will look into the parallizer.

Is that something that is highly recommended for a beginner, or do you think that money would be better spent on other accessories/eyepieces?

#5 dpwoos

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Posted 18 January 2013 - 10:21 PM

It is a great adapter, so if you need one then this is a worthwhile purchase. However, more important is a laser collimator. Again, if you need one of these then the Glatter is a great choice. Collimating is necessary, and many folks (including me) find a laser easy and effective. You can always use it with the adapter that you already have, and discover for yourself if the Parallizer is something that you need. I think that you do need it, but really it is best for you to figure that out for yourself.

#6 WaterMaster

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Posted 18 January 2013 - 10:37 PM

There are lots of reasons why a centering adapter is a good idea, especially for consistent collimation, and Howie builds some of the highest precision devices I've ever seen. I got a look at his Paralizer at ASAE and it's exactly what I'd expect from him. I can't compare it to any others as it's the only one I've actually laid hand on.

#7 Jon Isaacs

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Posted 19 January 2013 - 07:05 AM

Thanks for the responses, I will look into the parallizer.

Is that something that is highly recommended for a beginner, or do you think that money would be better spent on other accessories/eyepieces?


I don't recommend it. When you are collimating your scope, the secondary tilt is set with the laser, it is important that the laser be properly square with the focuser. This is not difficult to achieve by making sure the laser is properly seated in the drawtube. When setting the primary tilt with a laser, the Barlowed laser is the proper technique and again, it is just necessary to make sure the Laser is properly seated in the focuser.

If you are going to use a laser, what is important is that the laser itself is a high quality laser, that it fits the focuser without significant slop and that the laser itself is collimated. I recommend Howie Glatter laser collimators, I have two, one is about 12 years old and still going strong.

An 8 inch F/6 Newtonian has relatively relaxed collimation tolerances. You have better ways to spend your money.

Jon

#8 Mr Magoo

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Posted 19 January 2013 - 08:43 AM

Are these even in stock? His ad mentions "reserving" one.

#9 Ed D

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Posted 19 January 2013 - 08:44 AM

I agree with what Jon said and will add that a Cheshire tube and a collimation cap are all you really need to collimate your 8" f/6 scope. If you really want a laser then I agree with all the suggestions above. Don't waste your money on something cheap that will hurt collimation more than help. If the day comes that you get a big truss Dob you'll be glad you spent the difference on good tools.

Ed D

#10 kenrenard

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Posted 19 January 2013 - 03:39 PM

I bought one and own it. Got one when I bought my XT8 kit from orion. I use it for putting eyepieces in. It's really nothing special just more of a gadget. As the others have mentioned not worth spending the money on. I also have the orion laser collimator another newbie purchase at the start. As Jon mentions the lasers themselves are often not collimated. Mine is off by just a bit not terribly but I will no doubt by a Howie Glatter system when I can.
The XT8 is pretty easy to collimate once you get the hang of it. Spend some time reading in the forums and take a cloudy night and work on getting the collimation down. You should see the center ring on the primary with the collimation cap orion includes.



I would read this excellent thread below. It helps quite a bit with collimation.



http://www.cloudynig...rd=reflector...

If you need any more help. As in the forum and one of the more experienced folks ( not me!) can give some more tips.

Hope it helps

Ken

#11 dpwoos

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Posted 19 January 2013 - 06:13 PM

I bought one and own it. Got one when I bought my XT8 kit from orion. I use it for putting eyepieces in. It's really nothing special just more of a gadget. As the others have mentioned not worth spending the money on.


I think my Glatter Parallizer is absolutely worth it. Given that your laser collimator is not accurate then you might not realize how important it is to hold it parallel to the optical axis. Even a relatively small tilt will cause one to mis-collimate. All of this is not to say that I advocate that every newbie run out and buy one. It is always best to educate oneself, and a bit of struggle collimating might make the Parallizer's value obvious. Of course, maybe not and that is ok too.

#12 Adam Taylor

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Posted 19 January 2013 - 06:39 PM

Antares Twist-Lock Eyepiece Adapter, $31 shipped - same as Orion's Precision Centering Adapter. Easily my favorite add-on.

#13 Heitman

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Posted 19 January 2013 - 07:36 PM

Hi,
I have The Parallizer, and to me it works great. Without it, every time I put the laser in, the beam always ends up pointing to a slightly different place. Using The Parallizer, problem solved. Worth it to me.
Tim

#14 kenrenard

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Posted 19 January 2013 - 07:40 PM

I bought one and own it. Got one when I bought my XT8 kit from orion. I use it for putting eyepieces in. It's really nothing special just more of a gadget. As the others have mentioned not worth spending the money on.


I think my Glatter Parallizer is absolutely worth it. Given that your laser collimator is not accurate then you might not realize how important it is to hold it parallel to the optical axis. Even a relatively small tilt will cause one to mis-collimate. All of this is not to say that I advocate that every newbie run out and buy one. It is always best to educate oneself, and a bit of struggle collimating might make the Parallizer's value obvious. Of course, maybe not and that is ok too.



I don't have the gladder version. I do understand what you mean about the laser being out. I often have to adjust with the collimation cap. The laser gets me close.

I have heard good things about the gladder stuff. I still have much to learn with collimation so I may be missing some of the advantages.

#15 Jon Isaacs

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Posted 19 January 2013 - 07:43 PM

I think my Glatter Parallizer is absolutely worth it. Given that your laser collimator is not accurate then you might not realize how important it is to hold it parallel to the optical axis. Even a relatively small tilt will cause one to mis-collimate. All of this is not to say that I advocate that every newbie run out and buy one. It is always best to educate oneself, and a bit of struggle collimating might make the Parallizer's value obvious. Of course, maybe not and that is ok too.



The Newtonian Axial collimation tolerances for the focuser are not as tight as one might assume. For a Newtonian with out a coma corrector, Vic Menard states the tolerance is about 1/30th of the mirror diameter. For an 8 inch telescope this is close to 7mm. This is a radius, diameter would be 14mm which just happens to be the diameter of the reinforcing dot that typically marks the center of the mirror. With a Paracorr it would be 0.5% or about 1mm for an 8 inch. This is definitely doable a collimated laser that fits properly in the focuser.

More critical is the adjustment of the primary tilt. This should be done with a Barlowed laser which is insensitive to errors in the focuser/secondary alignment. For an F/6 telescope this needs to be within about 1 mm.

Catseye Collimation: Newtonian Axial Tolerances

Jon

#16 kenrenard

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Posted 19 January 2013 - 07:50 PM

Jon,
I have a question about the gladder collimator. Is the 1 1/4 or 2 the way to go. I have an XT8 may get a bigger dob someday. I read the article below and used this technique with a 2X barlow and a red filter with the paper disk cut out. I have also followed the other advise in the forums about looking through the focuser and seeing the whole primary mirror. I seem to be getting it very close and I am getting excellent views with my scope. Just curious on the Howie Gladder laser and TuBlug since they can get pricey.



http://www.cameracon...collimation.pdf


Thanks again for your advice.


Ken

#17 Jon Isaacs

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Posted 19 January 2013 - 10:52 PM

Is the 1 1/4 or 2 the way to go.



These days I think a 2 inch is the way to go unless you already have some scopes with 1.25 inch focusers. But I believe Howie Glatter makes a 1.25 inch-2 inch for the same price as the 2 inch alone so to me that makes sense.

I have two, my original 1.25 inch collimator is about 12 years old, the second one is a 2 inch 635nm that's about 5 years old. The 635nm is brighter to the eye, useful in collimating truss scopes during the day. With my big scope, it's 10 feet from the collimator to the mirror..

Jon

#18 dpwoos

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Posted 20 January 2013 - 12:54 AM

I think that it is best to hold one's collimator in the same way as one's high power eyepieces. So, since I use all 1.25" eyepieces for high power then I think my 1.25" collimator is exactly what I want - however the collimator sits in the focuser is how my 1.25" eyepieces sit.

On the focuser axial tilt thing, I don't see how this applies to the Parallizer and a laser collimator. We are not talking about properly collimating and then tilting only the eyepeice, but rather mis-collimating the secondary and then the primary because of a mis-aimed collimator. It really is the same case as having a wonky collimator.

#19 Jon Isaacs

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Posted 20 January 2013 - 03:31 AM

On the focuser axial tilt thing, I don't see how this applies to the Parallizer and a laser collimator. We are not talking about properly collimating and then tilting only the eyepeice, but rather mis-collimating the secondary and then the primary because of a mis-aimed collimator. It really is the same case as having a wonky collimator.


The secondary will be misaligned if indeed there is a problem with the fit of the focuser but Vic's tolerances allow for a significant error without a problem. This does not result in a miscollimated primary because the primary mirror should be adjusted using a Barlowed laser, not the return beam of the collimator.

The value of using the Barlowed Laser can easily be seen with a simple comparison. Insert the collimator into the focuser but make sure it is loose. While looking at the return beam on the collimator face, rock the collimator in the focuser. The return beam will be seen to dance across the face of the collimator.

The second step is to use the Barlowed laser, insert the Barlow with the target in the focuser, leaving it loose. Insert the laser into the Barlow and while watching the target on the face of the Barlow, rock the laser in focuser. This time, the dark shadow of the primary mirror center mark does not move on the face of the target even though the laser is moving about and the pattern on the primary can be seen to move.

This is the genius of the Nils Olof Carlin's Barlowed Laser Technique, it is only sensitive to the alignment of the primary mirror. Without the Barlowed Technique, accurate collimation of the primary with a laser is not possible because there are too many other factors involved, with the Barlowed Technique, it's pretty easy.

Jon

#20 kenrenard

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Posted 20 January 2013 - 07:42 AM

Thanks Jon,
I appreciate the advice.


Ken

#21 dpwoos

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Posted 20 January 2013 - 08:03 AM

The secondary will be misaligned if indeed there is a problem with the fit of the focuser but Vic's tolerances allow for a significant error without a problem.


What I read has nothing to do with a mis-collimated secondary, but rather only axial tilt at the focuser. I think you are confusing the two issues. Again, it seems obvious to me that a tilted collimator is EXACTLY the same issue as a collimator that is out of alignment, which I think everyone agrees is a bad thing. Would you be happy with a laser collimator that missed the center target when rotated? I don't think you would, and that is what we are talking about.

Also, this has nothing to do with the barlowed laser, which everybody agrees is the way to go.

#22 Jon Isaacs

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Posted 20 January 2013 - 09:00 AM

The secondary will be misaligned if indeed there is a problem with the fit of the focuser but Vic's tolerances allow for a significant error without a problem.


What I read has nothing to do with a mis-collimated secondary, but rather only axial tilt at the focuser. I think you are confusing the two issues. Again, it seems obvious to me that a tilted collimator is EXACTLY the same issue as a collimator that is out of alignment, which I think everyone agrees is a bad thing. Would you be happy with a laser collimator that missed the center target when rotated? I don't think you would, and that is what we are talking about.

Also, this has nothing to do with the barlowed laser, which everybody agrees is the way to go.


This is what you had written:

" We are not talking about properly collimating and then tilting only the eyepeice, but rather mis-collimating the secondary and then the primary because of a mis-aimed collimator. It really is the same case as having a wonky collimator."

The focuser axial alignment is the tilt of the secondary...

Ask yourself what happens if collimator is not exactly parallel optical axis, if it is a poor fit in the focuser. You adjust for it with the secondary tilt.

A slightly misadjusted axial alignment/secondary tilt does not result in a misaligned primary. That is why the Barlowed laser keeps entering in to it.

Jon

#23 dpwoos

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Posted 20 January 2013 - 12:14 PM

The purpose of the barlow+collimator is not to compensate for a mis-aligned secondary, but rather for SMALL mis-alignments of the collimator. I really do think you are missing the point of holding the laser collimator without tilt, as I am pretty sure that you would not be happy with a mis-aligned laser that produced exactly the same effect. Nobody thinks that a grossly mis-aligned collimator is ok because of the addition of the barlow.

#24 frito

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Posted 20 January 2013 - 01:45 PM

i bought a HOTECH 2" SCA and a Glatter Parallizer at the same time. am very happy with both of them.

to experiment with accuracy and repeatability of results i tried using the HOTECH on its own with its SCA's (Self Centering Adapters) the HOTECH fitted into the Parallizer and a Meade (GSO) laser collimator with and without the Parallizer.

The Meade collimator had to be fixed before it was useful it was not in collimation itself, after this every single configuration i tried agreed with each other close enough to be able to fine tune with a barlowed laser collimation to finish it off and perfect the primary alignment except for using the Meade without the Parallizer using a regular 2" to 1-1/4" adapter. i was able to resolve this issue as well however by applying scotch tape around the barrel of the Meade so it made a tight centered fit into my 1-1/4" adapter.

of all this methods of collimation the fastest and easiest one and the one i now use now is the HOTECH laser without its 2" adapter inserted into my Parallizer and fixed in place with the parallizer's hold down screw not the built in SCA compression rings. first i do it the normal way to make sure its very close to in collimation and then i remove the HOTECH and thread on the barlow element from my Orion Shorty 2x Barlow onto the end of the HOTECH (yep its threaded! how convenient) and finalize my primary alignment via Barlow method

a Glatter collimator and TuBlug i can see being an easier tool to use but it does cost more from what i gathered because you need not just the TuBlug but then a decent laser to put into the TuBlug (Glatter or otherwise) so you're looking at 200+ the HOTECH and a cheap barlow will get the same repeatable results for almost half the price albeit its less convenient to use due to having to tighten down the compression ring to attach and detach it but it is functional and works very well.

#25 Jon Isaacs

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Posted 20 January 2013 - 02:15 PM

The purpose of the barlow+collimator is not to compensate for a mis-aligned secondary, but rather for SMALL mis-alignments of the collimator. I really do think you are missing the point of holding the laser collimator without tilt, as I am pretty sure that you would not be happy with a mis-aligned laser that produced exactly the same effect. Nobody thinks that a grossly mis-aligned collimator is ok because of the addition of the barlow.


Dennis:

Did you read the Catseye link about collimation tolerances:

"A focuser axial error (FAE) tilts the eyepiece field stop (or image detector) relative to the focal plane. The result is a focusing error. The FAE is measured as the linear difference between the focuser axis (or more specifically, the eyepiece axis) and the center of the primary mirror. To keep the image defect contributed by FAE below that of the residual coma in the field of view, the FAE tolerance for a Newtonian telescope without coma correction is roughly 1/30th (3 percent) of the primary mirror diameter. Since there is (6X) less coma when a ParaCorr is used, the FAE tolerance should be reduced by a factor of six, or 0.005 times the diameter of the primary mirror when a coma corrector is used." (Letter to Jim Fry from Vic Menard)

This says that tolerance for the FAE, which can be adjusted by the secondary tilt, is 1/30th the mirror diameter. For an 8inch mirror, this is about 7 mm. This error could be in the collimator or in the adjustment. If one is using a Paracorr then it is about 1mm. It would seem that for


As far as the "grossly misaligned Collimator" used with a Barlow to set the primary tilt, the Barlow produces a diverging, diffuse beam, it does not require a perfectly aligned laser because it is diverging and diffuse. How this works as can be seen by the experiment previously outlined. Tilting the Barlowed Collimator in the focuser and observing the position of the shadow.

Jon






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