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Is Self Centering Adapter better for Collimating?

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#1 VectorRoll

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Posted 12 April 2013 - 02:22 PM

I am wondering if it is better to use a Self Centering Adapter when Collimating with a Laser Collimator over using a regular Compression Ring Adapter. Any thoughts?

I ask because when collimating today I noticed that when using my Laser when I tighten down the Laser in mt 1.25" Adapter I can see the laser point shifts position on the Primary and on the Diaginal in the Collimator. It also shifts when I turn the Adapter itself.

The Laser itself is collimated with a V-Block. At least it hits the same spot when rotating the Collimator and having the laser hit the wall a couple of feet away. I'll recheck the Laser at an even longer distance, but I am wondering if this is a common thing with compression rings, since the ring pushes the eyepiece on one or two sides.

I fear that they adapter making the Laser Collimator not being centered just makes the Collimation to always be off.

I am going to be buying a Cheshire as well as I wanted one anyways to learn how to use it as well. But I am wondering if getting a Self Centering Adapter to be a good Idea as well. Any thoughts on if a Self Centering Adapter is worth purchasing.

#2 Vic Menard

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Posted 12 April 2013 - 02:37 PM

I would suggest you consider this adapter: http://www.collimator.com and click on the link, "NEW - The Parallizer".

#3 Jon Isaacs

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Posted 12 April 2013 - 02:41 PM

But I am wondering if getting a Self Centering Adapter to be a good Idea as well. Any thoughts on if a Self Centering Adapter is worth purchasing.



It could be worth purchasing.

First I would make sure your laser is properly seated in the adapter. The laser has a shoulder that is supposed to fit up against the adapter, that is what ensures the alignment. Push on the laser and rotate it to make sure the shoulder is up against the adapter flange all the way around as you tighten up the adapter.

Jon

#4 VectorRoll

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Posted 12 April 2013 - 03:40 PM

I would suggest you consider this adapter: http://www.collimator.com and click on the link, "NEW - The Parallizer".

That is pretty nice. I watched the video on there site where the guy explains it. I like it plus it does not cost to much. I think I may just pick one of those up.

I wonder if they make a Focuser with it built in for 2" eyepieces.?

But I am wondering if getting a Self Centering Adapter to be a good Idea as well. Any thoughts on if a Self Centering Adapter is worth purchasing.



It could be worth purchasing.

First I would make sure your laser is properly seated in the adapter. The laser has a shoulder that is supposed to fit up against the adapter, that is what ensures the alignment. Push on the laser and rotate it to make sure the shoulder is up against the adapter flange all the way around as you tighten up the adapter.

Jon

If you saying to pretty much push it down all the way to the rim where it can not go any further, that is pretty much what I do for both the Collimator and 1.25" Adapter. I'll double check it though just to make sure. :)

#5 Vic Menard

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Posted 12 April 2013 - 03:58 PM

...I wonder if they make a Focuser with it built in for 2" eyepieces.?

That's a good question (and one I've discussed with Howie)--they don't, yet.
FWIW, my 2-inch tools and eyepieces seem to be less susceptible to registration errors than my 1.25-inch gear. But my Parallizer has fixed the 1.25-inch registration issues.

#6 DaveJ

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Posted 12 April 2013 - 04:29 PM

...I wonder if they make a Focuser with it built in for 2" eyepieces.?

That's a good question (and one I've discussed with Howie)--they don't, yet.
FWIW, my 2-inch tools and eyepieces seem to be less susceptible to registration errors than my 1.25-inch gear. But my Parallizer has fixed the 1.25-inch registration issues.


This part from Agena Astro works perfectly well, also.

#7 beatlejuice

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Posted 12 April 2013 - 05:48 PM

The Parallizer certainly works, but when I got the Self-centering adapter from Agena it worked as well. I would collimate with one or the other and then check with the one I didn't use to find that nothing had changed. This is after adjusting the secondary and also using the Tublug for primary adjustments. Some, (myself included), think that there is another advantage with the self-centering adapter with the ease of changing eyepieces. I'm keeping both since I like the confirmation aspect, but you might want to consider the other possible advantage to the self-centering adapter when you make a purchasing decision.

Eric

#8 Don Taylor

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Posted 12 April 2013 - 06:28 PM

My opinion (and only that) is that you should collimate with the same adapter you will subsequently use with your eyepieces.

The reason for this is that Collimation is aligning the optical axis of the scope's elements with that of the eyepiece

If you collimated with one centering adapter and then use a different one for viewing then you have just built in misalignment from any differences between the two.

Since You have checked the effect of rotating the Collimation tool and adapter together in the focuser and the point moves then I suggest you obtain a new adapter that can be used for both alignment and viewing.

Beyond that (as everything has some variation) it helps to orient eyepiece adapters exactly the same when using an eyepiece as when collimating taking care to register the adapter against the same feature of the focuser.

#9 johnnyha

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Posted 12 April 2013 - 09:42 PM

There are several schools of thought on this. I thought the same thing for awhile Don but came to realize, after reading many threads on this issue - the self-centering adapter is what works for me. You want the collimation to hit the center of the eyepiece (or the drawtube, if you will). The eyepiece can tilt quite a bit but it does not matter much, it's a "local tilt" and does not effect the image - the center is still pretty much centered and that is where the image is focused. However the laser OTOH when tilted by the setscrew, has to go all the way to the mirror (or lens), and any local tilt by the time it gets to the mirror has magnified by the distance and can be off quite a bit - and this can cause miscollimation of the return reflection, or the mirror might end up moved from its optimal position to accomodate the offset laser, or the secondary collimation may be thrown off.

#10 VectorRoll

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Posted 13 April 2013 - 09:55 AM

Well I tried to buy one of those Parallizer's but for the life of me it seems I can not register an account in order to get through the CheckOut process.
Anyone have an Idea on how to register with them in order to buy things from them?

If I can not figure it out I'll just go for the other one from Agena.

#11 Howie Glatter

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Posted 13 April 2013 - 10:13 AM

Hi Vector,

Sorry about the ordering problem - I'll try to fix it asap. In the meantime, you can just e-mail me at howieglatter@mindspring.com or phone at 718 796 3203.
I'm checking a batch into stock now. Each one is tested in a long path laser set up with a "perfect" 1.25" collimator inside it, rolling it within a "perfect" cylinder as a stand-in for a drawtube.
Regarding the O.P.'s question in the title of this thread, I think we should stop worrying about the centering, and instead worry about the tipping.

#12 Jon Isaacs

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Posted 13 April 2013 - 10:32 AM

However the laser OTOH when tilted by the setscrew, has to go all the way to the mirror (or lens), and any local tilt by the time it gets to the mirror has magnified by the distance and can be off quite a bit - and this can cause miscollimation of the return reflection,



This is one of the several reasons the return reflection should not be used for aligning the primary mirror... If one is going to use a laser, it needs to be some form of the "Barlowed laser" as it is relatively insensitive to misalignments other than the primary tilt.

Jon

#13 precaud

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Posted 13 April 2013 - 11:27 AM

You want the collimation to hit the center of the eyepiece (or the drawtube, if you will). The eyepiece can tilt quite a bit but it does not matter much, it's a "local tilt" and does not effect the image - the center is still pretty much centered and that is where the image is focused.


How can it possibly be true that the EP is so tolerant of axial misalignment as you suggest? It makes no sense to me.

#14 DaveJ

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Posted 13 April 2013 - 01:41 PM

How can it possibly be true that the EP is so tolerant of axial misalignment as you suggest? It makes no sense to me.


The eyepiece can tolerate a bit of tilt just fine. A tilted laser, on the other hand, causes extreme mis-collimation which screws up everything.

#15 Vic Menard

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Posted 13 April 2013 - 02:16 PM

The axial alignments are responsible for axial performance. The two axes are the optical, or primary mirror, axis, and the eyepiece axis (often referred to as the focuser axis).

Each axis has defined tolerances. For high magnification performance, the optical axis must be centered in the eyepiece field stop to a tolerance of +/-0.0055mm times the focal ratio cubed (Everhart). This effectively "centers" the coma "free" field in the center of the eyepiece field stop.

Similarly, for high magnification performance, the eyepiece axis must be tilted so it is aimed at the center of the primary mirror to a tolerance of about 3-percent of the primary mirror diameter (+/-). This tilt adjustment is usually imparted by adjusting the secondary mirror tilt. If a Paracorr is used, the tolerance is tightened by a factor of 6, or about 0.5-percent of the primary mirror diameter (+/-). This effectively keeps the defocusing contribution from a tilted focal plane below that of the coma contribution and ensures snap focus when combined with a well corrected optical axial alignment.

And I agree with Don Taylor that collimating tools should be subject to the same registration as the eyepieces or imaging accessories you'll be using with your scope. By using the same adapter for collimation and observing/imaging, the eyepiece/camera will benefit from the same axial alignment corrections.

#16 VectorRoll

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Posted 13 April 2013 - 02:52 PM

Hi Vector,

Sorry about the ordering problem - I'll try to fix it asap. In the meantime, you can just e-mail me at howieglatter@mindspring.com or phone at 718 796 3203.
I'm checking a batch into stock now. Each one is tested in a long path laser set up with a "perfect" 1.25" collimator inside it, rolling it within a "perfect" cylinder as a stand-in for a drawtube.
Regarding the O.P.'s question in the title of this thread, I think we should stop worrying about the centering, and instead worry about the tipping.

Thanks for the Reply. I went ahead and Emailed you.

Being the OP and since you mentioned the tiping. I take it you mean the laser itself. I just went through the collimation of the laser again to double check it. I know it is not as good as one of your laser's :) but if you have any further insight on how to improve any tilt I might have I am curious.

One thing about my Laser that I did notice is that when I took the end off today to see what size batteries it takes, which are dieing already even though I have only had it for about two weeks :foreheadslap: , I noticed that the laser is set in there at an angle. Yet when I do the V-Block test it does seem to be dead on. I have done the test at about twenty feet.
I am wondering is it common for the laser to coming out of the actual houseing at an angle like that?

#17 Howie Glatter

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Posted 13 April 2013 - 05:32 PM

". . since you mentioned the tiping. I take it you mean the laser itself"

I don't mean tipping of the laser beam with respect to the laser collimator housing. Let's theoretically assume a perfect collimator - I mean the tipping of the entire laser collimator, or eyepiece, or camera nosepiece, within the holder (drawtube or adapter). This is what creates the optical problems; not a small sideways offset of the accessory. As long as the axis remain parallel, you are o.k.
As has been mentioned, tip seems less of a problem for one-eyed visual observing. I think that's because of the capability of our visual system to accomodate small amounts of misfocus. Imaging chips can't do that yet :-) Tipping is a problem for high power bino-viewing, because the image moves in the field, and then inter-ocular collimation is lost. And of course, tipping is a terrible problem when using collimation tools.

"I noticed that the laser is set in there at an angle . . is it common for the laser to coming out of the actual houseing at an angle like that?"

Yes. Many low-quality laser collimators use cheap key-chain type laser pointers, which have infinitely permissive tolerance on beam alignment. They are typically powered by three small button cells that last many minutes.

Vector, at the moment I can receive but not send e-mail, so I will reply to your e-mail tomorrow, or send you a PM here.

#18 Starman1

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Posted 13 April 2013 - 05:38 PM

The Parallizer certainly works, but when I got the Self-centering adapter from Agena it worked as well. I would collimate with one or the other and then check with the one I didn't use to find that nothing had changed. This is after adjusting the secondary and also using the Tublug for primary adjustments. Some, (myself included), think that there is another advantage with the self-centering adapter with the ease of changing eyepieces. I'm keeping both since I like the confirmation aspect, but you might want to consider the other possible advantage to the self-centering adapter when you make a purchasing decision.

Eric

The self-centering adapter adequately centers and aligns the tool in the adapter, but the exterior of the adapter is still a smooth cylinder, and a fairly short one at that (to improve registration and safety for 2" filters threaded onto the bottom, I recommend using this adapter with an eyepiece barrel extender or a Baader Fine Tuning Ring. Both additions lengthen the adapter and improve its registration). In high-end focusers, the fit may be tight enough to avoid misregistration, but, unlike the Glatter Parallizer, it CAN still be mis-registered in the focuser's drawtube. Since any 1.25" collimation tool has the possibility of TWO misregistrations when used in a 2" focuser, I always recommend 2" tools with a 2" focuser.
The Glatter Parallizer may eliminate that objection, but if you have a 2" focuser, you might as well use 2" collimation tools.

As for the ease of changing eyepieces, I agree with you. The self-centering adapter is a smooth-sided collet, and, as such, doesn't hang up on the 'safety grooves' cut into eyepieces. Plus, unlike an adapter with a brass ring inside, it actually supports the eyepiece all the way to the shoulder.

#19 VectorRoll

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Posted 13 April 2013 - 06:05 PM

". . since you mentioned the tiping. I take it you mean the laser itself"

I don't mean tipping of the laser beam with respect to the laser collimator housing. Let's theoretically assume a perfect collimator - I mean the tipping of the entire laser collimator, or eyepiece, or camera nosepiece, within the holder (drawtube or adapter). This is what creates the optical problems; not a small sideways offset of the accessory. As long as the axis remain parallel, you are o.k.
As has been mentioned, tip seems less of a problem for one-eyed visual observing. I think that's because of the capability of our visual system to accomodate small amounts of misfocus. Imaging chips can't do that yet :-) Tipping is a problem for high power bino-viewing, because the image moves in the field, and then inter-ocular collimation is lost. And of course, tipping is a terrible problem when using collimation tools.

"I noticed that the laser is set in there at an angle . . is it common for the laser to coming out of the actual houseing at an angle like that?"

Yes. Many low-quality laser collimators use cheap key-chain type laser pointers, which have infinitely permissive tolerance on beam alignment. They are typically powered by three small button cells that last many minutes.

Vector, at the moment I can receive but not send e-mail, so I will reply to your e-mail tomorrow, or send you a PM here.

Thanks for your reply. Everything in it was very helpful for me. I am learning more every day.
I also look forward to your reply to my Email. :)

#20 beatlejuice

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Posted 13 April 2013 - 06:38 PM

I recommend using this adapter with an eyepiece barrel extender or a Baader Fine Tuning Ring.


Thanks Don,
I like the barrel extender idea. I didn't know about these. Pretty inexpensive and might be worth experimenting with. I also like the way it will solve the filter problem.

Eric

#21 VectorRoll

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Posted 19 April 2013 - 04:25 PM

Well I got my Paralizer from Howie Glatter today. :)
Great service by the way Howie. ;)

I am loving it. It works perfectly. It fits nicely in my 2" focuser and the 1.25" pieces fit nicely in it. The threading on the end is also perfect. I was able to attach my Barlow lens to it perfectlty and smoothly. So any 2" filters and extenson tube I may get should work perfectly as well.

Another thing is that it is just visibly beautiful. The milling work you all did on it is great. It looks perfect on my scope. Like it was meant to be a part of it.

The last thing I noticed is that the inset design allows for you to get about a 1/4" closer to the Secondary than you would with a flat end.

I have already used it to re-collimate my scope. Now I just need to get some ClearSkies in order to use it. :) !@#$%


If you all decide to make a 2" Focuser with this design, let me know. Or even some sort of Draw Tube Mod for my exsisting focuser. I would love to have it for my scope. :)

#22 precaud

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Posted 19 April 2013 - 09:45 PM

You have chosen... wisely... ;)

#23 Dakota1

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Posted 19 April 2013 - 10:36 PM

I got my Parallizer today and it is the best thing I have used. It is rock solid in the Moonlite focuser and the Glatter laser is solid. This is something everyone should have. I have tried the twist lock type of several makes. I tell you they will never do what this does for keeping the laser where it should be. This is a winner. Thank you Bill

#24 Jeff Morgan

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Posted 30 April 2013 - 09:44 PM

Last month I ordered a new FeatherTouch LW focuser, and came across the Parallizer on the Starlight web site. In theory it sounded great and I ordered it instead of the regular 1-1/4" adapter.

I just received my order, including the Parallizer. It is nicely made of course (I was told that Starlight Instruments does the manufacturing). Testing on Brandons and Delos reveals a very precise (tight!) fit. Obviously it is made to a high tolerance. Fit to the focuser is somewhat looser, but still very good. However I must say I have some apprehensions about it.

Firstly, the eyepiece end is a rather deeply inverted volcano top - this end is not shown in the advertisements. The depth could be very problematic for shorter eye relief eyepieces and/or eyeglass wearers. I tested it in the office with a 6 mm Brandon and I may be ok on this, but it needs to be verified under the stars.

Secondly and more troubling is the securing method. There is no compression ring, a brass set screw bears directly against the eyepiece barrel. The set screw appears to have some sort of rubberized coating dabbed on the tip, but how durable will that prove to be? I'm not keen on the idea of marring my eyepieces with set screw marks. Replacement with a nylon screw may be a better idea.

On a Dob there is no real danger of the eyepiece sliding out under gravity, so a very light touch on set screw will work. Or, I can just limit use to a laser collimator. But I can not see myself using this with eyepieces in my refractor where gravity can be an issue and therefore more tightening is required.

Since the scope I purchased this for will not be complete within normal return periods, I may just exchange it now for the regular FeatherTouch adapter.

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#25 Jeff Morgan

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Posted 30 April 2013 - 09:45 PM

Here is a photo showing a 6 Brandon well-recessed into the Parallizer.

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