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Is Self Centering Adapter better for Collimating?

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#26 Jeff Morgan

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Posted 30 April 2013 - 09:45 PM

One more angle to show the depth of the inverted volcano.

BTW, the new lightweight FT is a work of art!

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#27 okieav8r

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Posted 30 April 2013 - 09:53 PM

Brass is a softer metal than that of your eyepiece barrels, so it shouldn't mar them. When working on stainless steel aircraft parts, such as turbine shafts, mechanics use vices with brass jaws to hold parts while doing deburring and finish work on them, so that the parts will not be damaged. I've been using a Parallizer for two years, and it hasn't marred any of my eyepieces. And, due to the angle at which the set screw goes into the adapter, only a very light amount of applied pressure is needed to hold the eyepiece. Also, the pointed end of the screw is at such an angle that, for the most part, the flat of it is parallel to the eyepiece barrel. I have some University orthos that sit pretty low into the bowl of the adapter, but I haven't had any problems viewing through them. I'm going to purchase another Parallizer soon.

#28 Howie Glatter

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Posted 01 May 2013 - 05:13 AM

Hi Jeff,

"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 happy to tell you that you've got that wrong. The clamp screw has an acetyl (Delrin) tip, which is a very tough plastic, not a "rubberized coating", and it is permanently fixed deep into the brass screw. You can crank it down as hard as you like without danger of the metal contacting the eyepiece. So called "compression rings" do protect the eyepiece barrel from marring, but do not compress the eyepiece all around like a collet or split-ring, and create problems with eyepiece registration and eyepiece "saftey groove" lock-up.

"the eyepiece end is a rather deeply inverted volcano top - . . The depth could be very problematic"

In my opinion, you've got this wrong, too. The conical recess is there so that there is no loss of in-travel for situations where the eyepiece needs it. Eyepieces seat at the same depth as the 2" drawtube lip, as can be clearly seen in your photo.
The recess has to be conical in my design to clear the clamp screw shaft. While some eyepieces with wide upper bodies will not seat all the way down, they will still work fine with the Parallizer if the extra in-travel is not needed.

#29 Jeff Morgan

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Posted 02 May 2013 - 09:01 AM

Hi Jeff,

"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 happy to tell you that you've got that wrong. The clamp screw has an acetyl (Delrin) tip, which is a very tough plastic, not a "rubberized coating", and it is permanently fixed deep into the brass screw. You can crank it down as hard as you like without danger of the metal contacting the eyepiece. So called "compression rings" do protect the eyepiece barrel from marring, but do not compress the eyepiece all around like a collet or split-ring, and create problems with eyepiece registration and eyepiece "saftey groove" lock-up.



And I'm happy to say that you're right, and my concerns were unfounded. I tested this against anodized 6061-T6 tubing (a remnant of a truss tube purchased from Moonlight) and tightened it several times. From light contact to normal to as hard as I could finger-tighten the knob (which would never be done in actual use). No marks left on the aluminum. So long as the Delrin remains in place this should not marr an eyepiece barrel.

The impression that the tip was dabbed on was due to a flaw in the finishing process in the area of the screw passage. Perhaps oil from the thread cutting process remained in the threads after cleaning and leached out before the coating bath. The blem is on the internal surface and IMO in no way detracts from the product. I do have some past experience with metal coatings and know these things happen from time to time. Certainly not an issue worth complaining about (let alone a return) in any event.

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#30 Jeff Morgan

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Posted 02 May 2013 - 09:19 AM

"the eyepiece end is a rather deeply inverted volcano top - . . The depth could be very problematic"

In my opinion, you've got this wrong, too. The conical recess is there so that there is no loss of in-travel for situations where the eyepiece needs it. Eyepieces seat at the same depth as the 2" drawtube lip, as can be clearly seen in your photo.
The recess has to be conical in my design to clear the clamp screw shaft. While some eyepieces with wide upper bodies will not seat all the way down, they will still work fine with the Parallizer if the extra in-travel is not needed.


My concern was not about focus travel - I didn't even mention it.

Rather, the concern was about loss of eye relief on short focal length planetary eyepieces (of which the list is numerous). Even the twist mechanism for the Nagler Zoom is swallowed into the recess. I can adjust it with an ungloved hand, albeit awkwardly.

Since I have satisfied myself that the adapter will not marr eyepieces, I'll test the eye relief issue out this weekend in my refractor. Given the width at the top of the adapter, I'm hopeful that I can press the orbit of my eye deep enough in to see.

But would it be acceptable to not fully seat these types of eyepieces? For example, place the eyepiece in the adapter such that it is flush with the top?

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#31 Howie Glatter

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Posted 02 May 2013 - 01:20 PM

Hi Jeff,

Yes, you raise some very valid points about the Parallizer.

"So long as the Delrin remains in place this should not marr an eyepiece barrel."

I press fit the Delrin tip about 4mm into a hole in the screw end, and it took a while to get my machining tuned so that the press fit was super-tight with no danger of tip loss. I know of one failure from my first run where the tip worked loose and fell out. Fortunately, the user noticed it right away and did not mark an eyepiece. Although that problem is solved, if anyone experiences it, please contact me and I'll supply a good replacement screw.

"The impression that the tip was dabbed on was due to a flaw in the finishing process in the area of the screw passage."

Those marks, which your photo shows so embarrassingly well, are a consequence of the method that was used to remove any burr from the tapped hole, protruding into the 1.25" bore. We are working on a better method that will have little or no cosmetic consequence.

The issue of eye-socket clearance with the conical recess at the adapter top, when eyepieces with short relief and short upper bodies, like that one that you show are used, is something I had to compromise on in order to get to the design goal of no loss of in-travel. Hopefully, the clearance problem will not arise, or if it does, be very rare.

" would it be acceptable to not fully seat these types of eyepieces? For example, place the eyepiece in the adapter such that it is flush with the top?"

Of course! The Parallizer does not depend on the eyepiece bottoming-out to get great alignment.

I make the clamp screws, but you are correct, Starlight Instruments makes the Parallizer bodies for me. I want to take this opportunity to tell everyone how great Jon Joseph,the owner of Starlight has been in cooperating with me to produce the Parallizer. I have only manual machine tools, and I produced the first prototypes on them with great difficulty, transferring the lathe-turned adapter to the rotary table on my millling machine, to mill the Paralizer feature. I had to tweak the alignment of the adapter body to perfection with a very sensitve indicator when I clamped it to the rotary table in order to get it running true, so that the Parallizer would give the 2 arc minute alignment I was shooting for. If I did production this way, the Parallizers would cost $250.
Starlight has a CNC lathe with live axial tooling. It can produce a Parallizer in a single clamping, eliminating registration transfer errors. But this was not enough to hit 2 arc minute accuracy the first time. Even with the machine programmed to theoretically produce perfectly aligned features, the tiny tolerance necessary for 2 arc minute alignment was exceeded. This was where Jon went the extra light-year for me - I sent him a duplicate of the long path-length laser rig that I use to test and align collimators, and check Paralizers. After machining a Parallizer, He put it in the rig and determined how much it was off, and in which direction. He was then able to tweak his machine adjustments to bring it in, and consistantly hit and exceed the 2 arc minute criterion. This put a very big smile on my face, and I learned that it is not as easy to make high accuracy adapters as it is to make high accuracy collimators. By the way,in a stroke of brilliance, Jon was the one who came up with the name "Parallizer".

#32 SACK

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Posted 02 May 2013 - 01:21 PM

But would it be acceptable to not fully seat these types of eyepieces? For example, place the eyepiece in the adapter such that it is flush with the top?


Yes. After I got my Glatterizer and 1.25" glatter laser, I was curious about that, and inserted the laser into the glatterizer about halfway, turned it on, marked the position on the wall, turned it off. Then rotated it, again about halfway inserted, tightened it down, turn it on and it was johnny on the spot! It is the beauty of the design, it doesn't need large registration like others do.
Jonathan

#33 Jeff Morgan

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Posted 02 May 2013 - 03:38 PM

Thanks for the detailed reply Howie.

I guess I had a little shock with the idea that the eyepieces that would benefit most (the high power ones) might seat too deeply to be used. And the market as a whole has become accustomed to compression rings, so I may not be the only one needing re-education in the future.

Seating the eyepiece just a small distance taller in the adapter satisfies me completely. I must admit to feeling just a bit silly that such an obvious solution didn't immediately suggest itself to me, but it's good to hear from you this will not negate the benefits of the adapter.

I'm looking forward to using it for some high-power double star work tomorrow night in the refractor - and with my new Howie Glatter laser collimator.

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#34 Starman1

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Posted 02 May 2013 - 04:10 PM

Jeff,
Remember to follow the advice on how to insert the adapter, and only use one of your focuser's thumbscrews to tighten the adapter down or you will be defeating the purpose of the machined area on the outside of the adapter.

#35 nevy

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Posted 02 May 2013 - 04:49 PM

Good point don.
A question for howie, would it be possible or worthwhile making a 2" diameter paralyser as an aftermarket accessorie that screws into the top of the draw tube to replace the usuall compression ring and or the set screw type for us dob owners to get perfect registration on our2" focusers ?

#36 Howie Glatter

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Posted 02 May 2013 - 04:56 PM

For those who can't stop their fingers from using two clamp screws with the Parallizer, it is advised to rotate the Parallizer in the drawtube so that the two clamp screws are symmetrically disposed opposite the 1.25" clamp screw.

#37 Howie Glatter

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Posted 02 May 2013 - 05:10 PM

Hey Nevy,

"would it be possible or worthwhile making a 2" diameter paralyser as an aftermarket accessorie that screws into the top of the draw tube to replace the usuall compression ring and or the set screw type . ."

Possible, yes, if the top of the drawtube was threaded and had an accurate shoulder to screw down to.
Worthwhile, I don't know about that. I think the best place to put the Parallizer feature is right in the 2" focuser drawtube. If I were a conspiracy theorist, this whole thread might be a plot to lure focuser manufacturers into adopting the idea.
I am thinking of producing visual backs, camera nose-pieces, and larger size down-adapters with the Parallizer feature.

#38 REC

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Posted 02 May 2013 - 05:24 PM

Another booth I missed at NEAF:( I wanted to meet him!

#39 nevy

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Posted 02 May 2013 - 07:03 PM

Hey Nevy,

"would it be possible or worthwhile making a 2" diameter paralyser as an aftermarket accessorie that screws into the top of the draw tube to replace the usuall compression ring and or the set screw type . ."

Possible, yes, if the top of the drawtube was threaded and had an accurate shoulder to screw down to.
Worthwhile, I don't know about that. I think the best place to put the Parallizer feature is right in the 2" focuser drawtube. If I were a conspiracy theorist, this whole thread might be a plot to lure focuser manufacturers into adopting the idea.
I am thinking of producing visual backs, camera nose-pieces, and larger size down-adapters with the Parallizer feature.


I thought most focuser draw tube tops were threaded ( mine is ) I changed mine to a compression ring type , I would buy one if you could make em , I don't think theres any point for manufacterures of focusers to make them as they probly won't hit the accuracy that you aim for so it would be a wast of time , but I know you can do it.

#40 Starman1

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Posted 02 May 2013 - 07:45 PM

Alas, most focuser drawtube tops are not threaded. Many inexpensive refractors and reflectors have threaded focusers and a few dobs and newtonians from Synta, but they are the exception to the rule.
In order to make the focuser drawtubes the right way, many focusers would have to be redesigned to accept the different drawtube, and that probably isn't going to happen.

#41 Jeff Morgan

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Posted 02 May 2013 - 10:50 PM

Thanks for mentioning that Don - in the excitement of getting a new astro-toy (as witnessed by styrofoam peanuts all over the office floor), that one completely escaped me.

#42 Jon Isaacs

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Posted 03 May 2013 - 02:56 AM

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



Try it, loosen the eyepiece and tilt it while maintaining focus. The amount of tilt possible due to slop is small and does not affect the image...

As I have said before, proper alignment of a cylinder in a tube is best done by seating the shoulder of the eyepiece/adapter/collimator against the top of the focuser drawtube, this ensures that the eyepiece/adapter/collimator is parallel to the drawtube axis.

Jon

#43 Howie Glatter

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Posted 03 May 2013 - 04:40 AM

Hi Jon,

"proper alignment of a cylinder in a tube is best done by seating the shoulder of the eyepiece/adapter/collimator against the top of the focuser drawtube, this ensures that the eyepiece/adapter/collimator is parallel to the drawtube axis."

If the top face of the drawtube is square to the drawtube bore, and the drawtube bore is an accurate cylinder, this is fine.

In the unlikely though possible case that the face of the drawtube is not square with the bore, or if the drawtube bore has any taper, tightening the clamp screw may tip the eyepiece, forcing it out of 360 degree contact with the drawtube face.

#44 precaud

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Posted 03 May 2013 - 07:03 AM

I have four 2" to 1.25" adapters here. Three of them exhibit some combination of a) the top plate not being square to the drawtube, and B) the drawtube bore not being perfectly parallel to the outer adapter wall.

Since, when installed, the tool references the focuser drawtube, the top plate is guaranteed to reflect the inaccuracies of those other surfaces PLUS its own.

PS - I should have said, the Parallizer is the one good one.

#45 SACK

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Posted 03 May 2013 - 04:45 PM

A good tip there Howie.






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