36 replies to this topic

[areyoukiddingme]

I have a question about user collimation of triplet refractors.

 

The news I keep hearing--don't know if it's really true--is that Explore Scientific triplets can be collimated by users. Though sending back to the factory is always an option.

 

But then I have seen that Astrophysics video. Some dude called Roland takes as much as 5 hours to align optics to 1/10,000 of an inch (https://www.youtube....h?v=QX91KAAgFew)

 

What am I missing? Is it really possible for a user to align a triplet apo?

 

 

[jrcrilly]

It depends on what one is considering doing. If the objective cell has tilt/tip adjustments, it is no big deal to align the cell assembly to the tube. That is what is usually referred to as collimation.  If one is considering aligning the elements within the objective to each other, that is a different matter entirely and is best left to those with the appropriate experience and equipment.

[areyoukiddingme]

Ah . . . that makes a lot of sense . . . in that case, aligning the optics and the focuser should be relatively easy . . .

 

Thanks!

[Agatha]

Never tried it.  I hear it is very tricky.  

 

I betcha that "dude Roland" did a good job.  

[jrcrilly]

Ah . . . that makes a lot of sense . . . in that case, aligning the optics and the focuser should be relatively easy . . .

 

Thanks!

It can be a user adjustment. When folks speak of a collimatable cell, this is to what they are referring. Triplet objectives DO exist with individual lens centering adjustments, but (a) they can't be accessed while the cell is installed in a telescope so it's strictly a bench job, (b) they are uncommon, and © they should be left alone by almost everyone.

[gfeulner]

I read somewhere that triplets are hard to collimate even by the manufacturer and personally would not even think of doing it myself. I have an ES 102ED air spaced triplet. Collimating a doublet is a piece of cake. Done that a few times. Gerry

Edited by gfeulner, 25 December 2014 - 07:58 PM.

[Eddgie]

 When folks speak of a collimatable cell, this is to what they are referring. Triplet objectives DO exist with individual lens centering adjustments, but (a) they can't be accessed while the cell is installed in a telescope so it's strictly a bench job, (b) they are uncommon, and © they should be left alone by almost everyone.

 

 

The latest ES triplet 127ED does indeed come with radial centering adjustment screws.

 

The ES screws  are easily accessable with the lens cell mounted to the telescope.  The lens shade needs to be removed, but that is just three screws and it comes right off.

 

That being said (just giving the OP the facts about at least on ES model), I agree you 100%.   This is not something that most people should attempt.  The collimation of the lens elements to one another is extremely tedious to do.  You are moving two optical elements in two different planes against a third element, and getting it perfect is a painstaking process that takes an optical bench.  I do not belive it would be possible without a bench in double pass.

Now the OP may have been asking about normal collimation of the lens cell itself, and that is also possible with the ES 127.  The lens cell tilt screws are easily accessed even with the dew shield on.

 

Mine came in perfect lens cell collimation and did not need a bit of adjustment.  The centering screws are sealed into position by some kind of black thread lock material.

 

I normal use, I would hope that it never does need adjustment either for lens cell tilt or for radial centering, but it does have the necessary screws for both adjustments.  

Edited by Eddgie, 25 December 2014 - 05:08 PM.

[areyoukiddingme]

Thanks Eddgie . . . I'm anticipating the delivery of the ES 152Ed, hopefully soon. Given talk about collimation I wanted to get the low down just in case I find myself entertaining the idea. . . 

[Eddgie]

I agree with John C 100% that you would not want to ever touch the radial centering screws.  Play with the tilt screws all you want, but it would be a mistake to mess lens centering.   Even on a doublet it is hard to do.

 

If there is any decentering, you would want to return it.

 

Based on the fact that I rarely hear about centering problems, the scope is not likely to need it.  Likewise with tilt on the primary cell.   If it was set properly at the factory, the only way it would change is if you bent the tube.

 

Also, I only answered for the 127ED.  I do not know if the model you are getting has the centering screws, but even it if does, you should never have to mess with them.

[areyoukiddingme]

Centering the cell sounds like something that I can try if it should be necessary. But seeing that Roland Christen takes his sweet time getting a triplet collimated, there's just no way I'm ever even going to think of attempting it. 

 

This scope is a real indulgence for me, so I hope I'm just being a little paranoid and will report on first light. Fingers and toes crossed!

[jbalsam]

The ES 127 scopes that I had (I had two of them, one newer model and one older) do not have typical tip/tilt adjustment screws (i.e. collimation screws). As several people have said they have lens centering screws, which are designed for screwing up your lens cell if you mess with them. 

 

Bottom line is you can't collimate an ES127 (and probably a few other of their lens cells) without something on the focuser end. I had a Stellarvue 115 that was similar (no tip/tilt adjustment on the lens cell, only lens centering screws), but the focuser had push/pull screws designed into it to allow you to adjust collimation. 

 

EDIT: the ES AR152 had a push-pull style lens cell and lens centering adjustments. That was pretty easy to work with. 

Edited by jbalsam, 26 December 2014 - 03:07 PM.

[Astrojensen]

 

Triplet objectives DO exist with individual lens centering adjustments, but (a) they can't be accessed while the cell is installed in a telescope so it's strictly a bench job, (b) they are uncommon, and © they should be left alone by almost everyone.

ALL triplet objectives have individual lens centering (unless it is cemented), also oil spaced ones, though some may only have adjustment for the middle one. I have not ever heard of an airspaced triplet lens that did not have adjustments for each lens.

 

a) depends on the lens cell design, but I agree it's basically a bench job.

 

b) no, they are very common, as explained above, but may not be immediately obvious to a casual inspection. 

 

c) yes, they should not be touched by anyone not 100% sure of what he's doing. 

 

 

This said, triplets CAN be centered, using a star as reference. This is what was done before interferometers where invented. Remember, some of the first commercial available achromats were the triplets from Dollond, made in the 1770'ies, way before the interferometer was invented. A friend of mine has taken one apart and realigned it, using an artificial star. It was extremely painstaking and took a lot of time. He had to make a new cell, because they had to cut the old one apart. 

 

 

Clear skies!

Thomas, Denmark

Edited by Astrojensen, 26 December 2014 - 03:41 PM.

[astrophile]

Centering the cell sounds like something that I can try if it should be necessary. But seeing that Roland Christen takes his sweet time getting a triplet collimated, there's just no way I'm ever even going to think of attempting it. 

 

This scope is a real indulgence for me, so I hope I'm just being a little paranoid and will report on first light. Fingers and toes crossed!

 

At the risk of taking this thread OT, what mount and what eyepiece collection are you planning to use with the 152?  Very interested to hear first light experience, thanks!

[areyoukiddingme]

I have a skywatcher sky-tee 2 (it easily deals with my 11" edge). For heavy duty use I have it on a cgem-dx tripod. Still, I will probably need to get an extension tube for the refractor (I also have the German Equatorial, but I rarely use it).

 

As far as eyepieces go I think my Leica zoom should get a lot of use. I also have binoviewers and plan to try that out for planetary and deep sky given that it should give a reasonably wide field of view compared to the SCT. Other than that most used stuff is a 31mm Nagler, and Explore Scientific 100 degree (9, 14, 20). A 4.7 Ethos will be my high power eyepiece.

 

My hope is that I will be able to reach focus in eyepieces with the .7 FF/FR. That arrived already. 

 

Anyway, I will start a new thread when it arrives. I contacted ES and they said they were planning late December/Early January, but that they'd get back to me on that.

[MFCharon]

With a Cheshire I see two donuts just touching eachother. That's not good (enough). But now comes the question; which of these screws (if any) I need to change to align? It looks like none of them is giving any result. If I'm correct I can remove the front with screw 1 (and the others around the cell). But for what are screw 2 and 3?

 

Edited by MFCharon, 07 July 2017 - 02:27 AM.

[T1R2]

With a Cheshire I see two donuts just touching eachother. That's not good (enough). But now comes the question; which of these screws (if any) I need to change to align? It looks like none of them is giving any result. If I'm correct I can remove the front with screw 1 (and the others around the cell). But for what are screw 2 and 3?

 

I'm not familiar with that lens cell but, if its not getting results, it because its either glued, and/or also you must not turn one in without adjusting the one on the other side out, if you didn't do this it could possibly chip or crack the lens since the screws are in direct contact with the lens edges. or at the very least pinch the lens

 

these are the centering screws being discussed, and should not be attempted, just send it in

 

however the collimating tilt screws on front of the scope can be used, people adjust the tilt (collimation) of their scopes all the time when needed.

 

if you do want to attempt this then do research as much as you can handle online and with ES, only after you are confident should you proceed. please note it can take more than one attempt to get it right maybe even hrs or few days of fiddling

[HARRISON SCOPES]

 

 

Triplet objectives DO exist with individual lens centering adjustments, but (a) they can't be accessed while the cell is installed in a telescope so it's strictly a bench job, (b) they are uncommon, and © they should be left alone by almost everyone.

ALL triplet objectives have individual lens centering (unless it is cemented), also oil spaced ones, though some may only have adjustment for the middle one. I have not ever heard of an airspaced triplet lens that did not have adjustments for each lens.

 

a) depends on the lens cell design, but I agree it's basically a bench job.

 

b) no, they are very common, as explained above, but may not be immediately obvious to a casual inspection. 

 

c) yes, they should not be touched by anyone not 100% sure of what he's doing. 

 

 

This said, triplets CAN be centered, using a star as reference. This is what was done before interferometers where invented. Remember, some of the first commercial available achromats were the triplets from Dollond, made in the 1770'ies, way before the interferometer was invented. A friend of mine has taken one apart and realigned it, using an artificial star. It was extremely painstaking and took a lot of time. He had to make a new cell, because they had to cut the old one apart. 

 

 

Clear skies!

Thomas, Denmark

 

LZOS have no adjustment in the air spaced triplets up to and including the 8" - just a very precisely engineered cell which is stepped internally to compensate for the thermal expansion rates of each element, superbly done.

[turnerjs085]

Be really careful with those screws. As already said, you can cause substantial damage to the lens during adjustment. Make sure that you loosen any axial retaining ring a bit, otherwise it will prevent the lens from being able to tip/tilt as you translate an element. Try to visualize the movement as you slide an element with curved surfaces against another curved surface. It not only moves sideways, but tips as it follows the curves. If you are really committed to diy on this one, it may be worth taking the cell apart to learn how it works before continuing. Damage happens when you -almost- understand how something functions Just be aware that without lab tools and methods, this is potentially going to take a lot of trial and error (keep detailed notes).

Anyway, I would guess that the two rings seen in the cheshire are the back and front of the objective. If so, it is telling you that s1 and s6 are misaligned. What do you see in a star test? This is kinda the issue with a cheshire for triplets, you have 4 surfaces you can't see... I suspect that for anything other than gross inital alignment, a star test is going to the primary tool used.

As far as which screw to adjust, it almost looks like screw 1 is a lock screw for that front ring. Is that ring the retainer, or is there another retainer in front or in back of the lens? If that is the case, it looks like the back element is non adjustable, which is totally reasonable if it locates on the OD and a lens seat. I would start with the center element, as I have had the best luck there. Use it to correct coma, then iterate to the front element to correct any residual lateral color. If that seems to get worse, reverse the order of operations. Just be aware that the center element is frequently the ED glass, and it is substantially softer than a crown glass.

Jeremy

[Jared]

Centering the cell sounds like something that I can try if it should be necessary. But seeing that Roland Christen takes his sweet time getting a triplet collimated, there's just no way I'm ever even going to think of attempting it.

This scope is a real indulgence for me, so I hope I'm just being a little paranoid and will report on first light. Fingers and toes crossed!

Getting the elements centered with respect to each other is a pain with a doublet since tolerances are very tight. However it is doable since you only have one variable to work with. A triplet? As everyone else has mentioned, I wouldn't touch it.

By the way, centering is only required with air spaced triplets. On an oiled telescope it's a non issue. Some of Roland's designs are oiled. One of them--the current 130--is what's known as a broken triplet, meaning one oiled space and one air space.

Collimating the lens cell with respect to the optical tube (or the focuser with respect to the tube and cell) is fairly easy with a laser, but is not all that important as long as you are pretty close. I might pay a little attention if this were annimaging scope with a large chip camera since you might see some star bloat and astigmatism in the corners of it is off. Unless it's bad, though (and it's not likely to be without a serious knock), you'd never notice anything visually.

Just enjoy your 152 when it arrives. It is unlikely that the optics will ever require an adjustment. That's the beauty of refractors.

[Jeff B]

 

 

 

Triplet objectives DO exist with individual lens centering adjustments, but (a) they can't be accessed while the cell is installed in a telescope so it's strictly a bench job, (b) they are uncommon, and © they should be left alone by almost everyone.

ALL triplet objectives have individual lens centering (unless it is cemented), also oil spaced ones, though some may only have adjustment for the middle one. I have not ever heard of an airspaced triplet lens that did not have adjustments for each lens.

 

a) depends on the lens cell design, but I agree it's basically a bench job.

 

b) no, they are very common, as explained above, but may not be immediately obvious to a casual inspection. 

 

c) yes, they should not be touched by anyone not 100% sure of what he's doing. 

 

 

This said, triplets CAN be centered, using a star as reference. This is what was done before interferometers where invented. Remember, some of the first commercial available achromats were the triplets from Dollond, made in the 1770'ies, way before the interferometer was invented. A friend of mine has taken one apart and realigned it, using an artificial star. It was extremely painstaking and took a lot of time. He had to make a new cell, because they had to cut the old one apart. 

 

 

Clear skies!

Thomas, Denmark

 

LZOS have no adjustment in the air spaced triplets up to and including the 8" - just a very precisely engineered cell which is stepped internally to compensate for the thermal expansion rates of each element, superbly done.

 

I believe, Thomas Back had a big influence there.  

[MFCharon]

 

 

 

these are the centering screws being discussed, and should not be attempted, just send it in

 

however the collimating tilt screws on front of the scope can be used, people adjust the tilt (collimation) of their scopes all the time when needed.

 

 

"These are the centering screws..." => which number?

 

"however the collimating tilt screws" => number 1?

 

I think screw 1 is just a front ring locking screw.

[T1R2]

 

 

 

 

these are the centering screws being discussed, and should not be attempted, just send it in

 

however the collimating tilt screws on front of the scope can be used, people adjust the tilt (collimation) of their scopes all the time when needed.

 

 

"These are the centering screws..." => which number?

 

"however the collimating tilt screws" => number 1?

 

I think screw 1 is just a front ring locking screw.

 

centering screws- #2

 

collimation screws - not shown

 

I also think that 1 was a locking screw

[Astrojensen]

 

 

 

Triplet objectives DO exist with individual lens centering adjustments, but (a) they can't be accessed while the cell is installed in a telescope so it's strictly a bench job, (b) they are uncommon, and © they should be left alone by almost everyone.

ALL triplet objectives have individual lens centering (unless it is cemented), also oil spaced ones, though some may only have adjustment for the middle one. I have not ever heard of an airspaced triplet lens that did not have adjustments for each lens.

 

a) depends on the lens cell design, but I agree it's basically a bench job.

 

b) no, they are very common, as explained above, but may not be immediately obvious to a casual inspection. 

 

c) yes, they should not be touched by anyone not 100% sure of what he's doing. 

 

 

This said, triplets CAN be centered, using a star as reference. This is what was done before interferometers where invented. Remember, some of the first commercial available achromats were the triplets from Dollond, made in the 1770'ies, way before the interferometer was invented. A friend of mine has taken one apart and realigned it, using an artificial star. It was extremely painstaking and took a lot of time. He had to make a new cell, because they had to cut the old one apart. 

 

 

Clear skies!

Thomas, Denmark

 

LZOS have no adjustment in the air spaced triplets up to and including the 8" - just a very precisely engineered cell which is stepped internally to compensate for the thermal expansion rates of each element, superbly done.

 

I had a 100/800 TMB in APM CNC tube on loan for a year or so. It most definitely had centering screws on the lens cell. 

 

EDIT: No, not centering screws, but small rubber pads to keep the lenses centered and stop them from accidentally rotating. 

 

 

Clear skies!
Thomas, Denmark

Edited by Astrojensen, 07 July 2017 - 02:37 PM.

[HARRISON SCOPES]

I have respaced and cleaned all air to glass surfaces on several LZOS triplets including a 115 130 152 and 203 and all had none due to a well designed cell and careful shamfer of the lens edges. I have also seen many more out of the cell. Some had blanked holes with rubber bungs which at a glance may look like screws, these holes were used to move elements over the steps during assembly but I have never seen radial screws in the cells. It is possible some may have as they were produced for many years and production may have changed. From memory I believe the 254 or 306 may have.

Edited by HARRISON SCOPES, 07 July 2017 - 02:37 PM.

[Astrojensen]

I have respaced and cleaned all air to glass surfaces on several LZOS triplets including a 115 130 152 and 203 and all had none due to a well designed cell and careful shamfer of the lens edges. I have also seen many more out of the cell. Some had blanked holes with rubber bungs which at a glance may look like screws, these holes were used to move elements over the steps during assembly but I have never seen radial screws in the cells. It is possible some may have as they were produced for many years and production may have changed. From memory I believe the 254 or 306 may have.

You are probably right. I actually did some research and memory digging and edited my post before I saw your reply here. 

 

 

Clear skies!
Thomas, Denmark