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From undercut to smooth barrels: possible?

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#1 Traveler

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Posted 03 April 2020 - 12:41 AM

Is it possible to change EP's with those undercut barrels into smooth barrels by buying seperate smooth barrels and so change those silly undercut barrels?

If possible, where could i buy those seperated smooth barrels?   



#2 MarkGregory

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Posted 03 April 2020 - 12:58 AM

I can’t answer your question. However, I do find it interesting that so many people hate these undercut barrels. They don’t bother me at all. I actually see the undercuts as a good thing, especially if you do outreach for children. They like to touch the scope and eyepieces and you never know what will happen under dark skies. Having an ocular slip out onto a hard surface is not a fun thing to imagine. Anyway, I look forward to seeing the responses you receive from other members. Mark


Edited by MarkGregory, 03 April 2020 - 01:01 AM.

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#3 Bob4BVM

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Posted 03 April 2020 - 01:04 AM

I'd have to do some actual investigation into commercial models, but I have been using pre=made smooth barrels from SurplusShed in my DIY EP builds f or several years now.  I use both their 1.25 and 2 inch barrels. their barrels have fully filter-threaded ID's which might work on some commercial EP top assemblies. If EP top housings have internal thread attachments then the SS barrels will need to have external matching threads cut to fit EP  in question.

 

Of course new barrels and even all new housings can be made from scratch if you have a lathe. 

Bino EP cnvrsn hsg3.jpg Bino EP cnvrsn hsg4.jpg

 

 

 

Another possibility is certain cases is to just reverse the barrel to put the indent at the top where it may be less of a problem.

EP undrcuts reversed.jpg

 

 

CS

Bob


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#4 Traveler

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Posted 03 April 2020 - 01:11 AM

Reversing the barrel! I have to investigate if that is possible with my ep's. Thanks for the tip Bob!



#5 emilslomi

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Posted 03 April 2020 - 02:24 AM

Undercut and smooth barrels are like matte and glossy computer screens. First, all screens were matte, then glossy was a feature that you paid extra for, and now, matte screens are a feature that you pay extra for. I see that they are suited to different uses. I don't really care one way or the other ... with eyepieces (screens have to be matte!). What really makes me curious is how so many people seem to be bothered by the undercuts. I have a fair selection of eyepieces and diagonals, but I literally never ever had a problem with the undercuts. What are you guys doing? I'd like to try to understand :-)

 

Emil


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#6 sg6

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Posted 03 April 2020 - 02:50 AM

If you can find a supply of smooth ones with the right thread changing is literally just that.

Actually if you had say 4 or more a small workshop might make a number up. Ask around as cost vary a lot - I found that on a small job. One place said £50 the next did it then and there for free.

 

You do not need the barrell chromed, you can blacken the internal thread.

 

Personally they do not bother me at all. Actually have no idea which ones I have that are smooth or undercut. To me the differentce seems to be an extra turn of the retaining screw. So nothing. Shiny end goes in focuser, tighten whatever. End of it.


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#7 markb

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Posted 03 April 2020 - 04:38 AM

Other than having to barrels custom machined, we can be challenging to replace barrels. We're recent eyepiece designs from China seem to be more likely to share common thread pitches. Your paragraph I tried to replace damaged barrels in the past, and going through a fairly extensive assortment of eye pieces, it was extremely hard to find a match. I ended up having to advertise for damaged eye pieces of one design as the only possible solution to replacing a missing barrel.

 

I am among the undercut haters, but that's me, opinions in the following thread opinions vary wildly.

 

The good part about the thread is that it contains several excellent solutions to the problem, although tapered undercuts remain a more challenging problem.

 

I don't recall if the approach was mentioned within the thread, but I plan to measure and custom generate taper eliminators using a 3D printer.

 

https://www.cloudyni...from-the-start/


Edited by markb, 03 April 2020 - 04:42 AM.


#8 TOMDEY

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Posted 03 April 2020 - 06:37 AM

The conundrum is that there are now no standards at all, other than the (roughly) 0.965, 1.25, 2, and 3-inch diameters. So the focuser, eyepiece, collimation tools, and filter manufacturers are completely guessing. They also make the prudent assumption that modern amateurs are too stupid to lock their eyepieces in, before swinging the telescope around. That results in all sorts of seating mis-match problems:

 

>loose and wobbly

>won't bottom in

>hits diagonal mirror

>tilts when you tighten the thumbscrew

>gets hung up inserting or extracting... sometimes entirely stuck

 

Also explains why some users declare there is no problem... because their limited selection currently works OK. Then they upgrade to the next better make and model, and discover one eyepiece falls out, and the other is hopelessly stuck. The best solution would be to go back to smoothies. Then the customer can opt to machine grooves in, to match their equipment. Which actually means that 99% would just develop the habit of tightening them in.    Tom


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#9 russell23

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Posted 03 April 2020 - 10:05 AM

Is it possible to change EP's with those undercut barrels into smooth barrels by buying seperate smooth barrels and so change those silly undercut barrels?

If possible, where could i buy those seperated smooth barrels?   

I completely solved the undercut defect problem with this purchase: 

 

https://agenaastro.c...2-125-blue.html

 

I have not had a single problem with the undercuts snagging with compression ring grooves since I made this purchase.  It has been one of the best purchases I have made to remove an annoyance from my observing! 


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#10 Eddgie

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Posted 03 April 2020 - 10:07 AM

Tom has really put the real issue in the spotlight.

 

I have had cases where I was able to find smooth barrels on eyepiece pairs (I used to only view with binoviewers before going to image intensified eyepieces) that had the same attaching thread as eyepieces I wanted to use that had undercuts, so when I was lucky enough, I could swap them.   

 

To Tom's point though, no one sells just the barrels, and the only way to do it would be to try to find eyepeices without undercuts that happened to have the same treading as the eyepieces you want to covert.

 

But that is not really practical, is it.  So, in a general sense, the answer to your question is no, you can't buy barrels alone on the open market.

 

(Another important point is that in many eyepieces, the eyepiece barrel itself is the retaining ring for the lenses, and in some cases, it has the field stop built into it. It really is not something that lends itself to easy marketing.)



#11 Eddgie

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Posted 03 April 2020 - 10:10 AM

I completely solved the undercut defect problem with this purchase: 

 

https://agenaastro.c...2-125-blue.html

 

I have not had a single problem with the undercuts snagging with compression ring grooves since I made this purchase.  It has been one of the best purchases I have made to remove an annoyance from my observing! 

You completely solved the undercut problem for you maybe, but not for everyone.  This solution won't work for 1.25" diagonals or binoviewers, and often, this is where the problem is most severe.

 

It is though a good way to deal with it for someone that is using a 2" diagonal and would be using a 2" to 1.25" adapter anyway though, so yeah, a nice piece of gear



#12 csrlice12

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Posted 03 April 2020 - 10:11 AM

If the barrels have lenses in them, unless you fill in the undercut with something, you're basically SOL.



#13 russell23

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Posted 03 April 2020 - 10:27 AM

You completely solved the undercut problem for you maybe, but not for everyone.  This solution won't work for 1.25" diagonals or binoviewers, and often, this is where the problem is most severe.

 

It is though a good way to deal with it for someone that is using a 2" diagonal and would be using a 2" to 1.25" adapter anyway though, so yeah, a nice piece of gear

Well I did use "I" throughout my post to indicate how "I" felt about the solution I chose to eliminate the problem for me.  

 

Now if I get another Baader 1.25" prism diagonal the problem will return,  but I won't do that unless I decide to get a 60-72mm aperture APO.  

 

Edit to add:

 

For those that are using a 1.25" star diagonal.  This is a possible solution to the undercut issue: 

 

https://agenaastro.c...-extension.html

 

It would not necessarily eliminate all the catching because I find that the barrels will catch the compression ring groove on insertion and then the undercut catches the groove on extraction.  But this might shift the undercut above the compression ring so that the eyepiece barrel is not tipped by the ring. 


Edited by russell23, 03 April 2020 - 10:30 AM.


#14 Starman1

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Posted 03 April 2020 - 01:12 PM

Is it possible to change EP's with those undercut barrels into smooth barrels by buying separate smooth barrels and so change those silly undercut barrels?

If possible, where could I buy those separated smooth barrels?   

Not on eyepieces with lenses in the lower barrel.

On many simple eyepieces with no lenses in the barrels, the answer is "maybe".

The reason is, some barrels thread into the top sections, some thread over the top section, and there are absolutely no

common threads used in the astronomy world.  I suspect the different threadings are almost as numerous as the eyepieces themselves.

Worse, almost all eyepieces today have some form of undercut on the barrel--either cylindrical or conical.

So finding a cheap used eyepiece to steal the barrel from would be unlikely.

 

No one actually markets what you want, and even if you found someone who did, it is unlikely the threads would work on your eyepieces.

So it would be easier to pay a local machine shop to make what you want, but you'd have to wait until they can reopen.

 

So, what are solutions?

--metal tape applied to fill the undercuts.  This works.

--use 1.25" adapters that have internal collets (called Twist-Lock) that seem to have no trouble with undercuts.  I use one in my refractor and it works on all eyepieces.

--remove the brass split ring from the focuser and replace the screws with nylon one (or nylon-tipped).  Doesn't completely solve the problem, but it's a bit better.

--replace your eyepieces with ones that have smooth barrels (there are a few, like Vixen SLVs)

 

Hope that helps.


Edited by Starman1, 03 April 2020 - 01:12 PM.

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#15 TOMDEY

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Posted 03 April 2020 - 03:58 PM

Oh how I miss the days when I was working! Most of my work was prototype optics, leading to later production runs. One magnificent benefit of that was bonding with the best tool and die makers the corporations had in their stables. They occasionally turned out custom parts for my off-line home experiments. Not only did management allow it, they downright encouraged it! Those days are long gone. But a good machinist with a thread-cutting lathe could certainly retrofit smoothies to most eyepieces.

 

Here's a rather extreme concept, which a high-end machinist could handle: Turn down the barrel below the various undercuts, to the slip-fit of some standard precision e.g. 2" OD tubing sleeve (brass, stainless?) Epoxy that sleeve on. The details of just how to do that would be in the machinist's hands. The guys at work had done far more complex surgeries on some of my stuff, without even removing the optics, dismembering, or getting anything dirty or oily! When they would start, I'd get out of the area so as not to bother them with worries or questions.    Tom



#16 Starman1

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Posted 03 April 2020 - 04:41 PM

You can eliminate all undercuts by attaching 2" adapters without undercuts to all 1.25" eyepieces.

But eliminating the grooves on 2" eyepieces would be a different issue.

Tom's idea might be possible, but ONLY if the barrel is thick enough to hold the optics when reduced to the diameter of the undercut's bottom.


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#17 Kunama

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Posted 03 April 2020 - 04:45 PM

I solved the undercut problem in two ways, I only use Tak  eyepieces in my Tak 1.25" prism star diagonal and Baader Clicklocks in my three 2"  star diagonals......

 

On my FTF2015BCR attached to my Dob I removed the brass compression band, then rounded the inside edges with some 360 grit emery paper and reinstalled it,  it was only due to the sharp edges that it would catch occasionally.


Edited by Kunama, 03 April 2020 - 04:55 PM.

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#18 B 26354

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Posted 03 April 2020 - 05:48 PM

I completely solved the undercut defect problem with this purchase: 

 

https://agenaastro.c...2-125-blue.html

 

I have not had a single problem with the undercuts snagging with compression ring grooves since I made this purchase.  It has been one of the best purchases I have made to remove an annoyance from my observing! 

Only problem is... that adapter itself has "a 2" tapered barrel". So it is also undercut.

 

Fortunately, Agena also sells this one, which doesn't:

 

https://agenaastro.c...ce-adapter.html

 

...and this one, which has more precise machining:

 

https://agenaastro.c...ce-adapter.html

 

grin.gif


Edited by B 26354, 03 April 2020 - 05:58 PM.


#19 Starman1

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Posted 03 April 2020 - 06:03 PM

Only problem is... that adapter itself has "a 2" tapered barrel". So it is also undercut.

 

Fortunately, Agena also sells this one, which doesn't:

 

https://agenaastro.c...ce-adapter.html

 

...and this one, which has more precise machining:

 

https://agenaastro.c...ce-adapter.html

 

grin.gif

The last one does not have a collet that extends all the way to the opening for the eyepiece.

As a result, it only clamps below the undercut--NG.

The Antares is better because it also clamps above the undercut.


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#20 B 26354

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Posted 03 April 2020 - 06:13 PM

The last one does not have a collet that extends all the way to the opening for the eyepiece.

As a result, it only clamps below the undercut--NG.

The Antares is better because it also clamps above the undercut.

Thanks for that. How about this one?:

 

https://luntsolarsys...epiece-adapter/

 

...or this?:

 

https://www.bhphotov...25_adapter.html


Edited by B 26354, 03 April 2020 - 06:26 PM.


#21 russell23

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Posted 03 April 2020 - 06:32 PM

Only problem is... that adapter itself has "a 2" tapered barrel". So it is also undercut.

 

Fortunately, Agena also sells this one, which doesn't:

 

https://agenaastro.c...ce-adapter.html

 

...and this one, which has more precise machining:

 

https://agenaastro.c...ce-adapter.html

 

grin.gif

A taper is not an undercut.  A tapered barrel is not as good as a smooth barrel, but is better than an undercut - and the taper is generally not an issue on a 2” OD barrel.  Certainly there can be seating/tipping issues with a 1.25” tapered barrel. Although I have never had an issue with a 1.25” taper either.   The taper on the WO roto-lock not been an issue with my star diagonal.  Like I said, It has eliminated my issues with undercuts completely.

 

The other thing about the WO version is the finger grips that make it very easy to twist.

 

But pick the one you like.  The important point is this style of adapter eliminates 1.25” eyepiece hang ups. 


Edited by russell23, 03 April 2020 - 06:32 PM.


#22 B 26354

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Posted 03 April 2020 - 06:50 PM

A taper is not an undercut.  A tapered barrel is not as good as a smooth barrel, but is better than an undercut - and the taper is generally not an issue on a 2” OD barrel.  Certainly there can be seating/tipping issues with a 1.25” tapered barrel. Although I have never had an issue with a 1.25” taper either.   The taper on the WO roto-lock not been an issue with my star diagonal.  Like I said, It has eliminated my issues with undercuts completely.

 

The other thing about the WO version is the finger grips that make it very easy to twist.

 

But pick the one you like.  The important point is this style of adapter eliminates 1.25” eyepiece hang ups. 

Got it. Sorry. I get the difference... I just have always lumped the two into the same "potentially disruptive" category. None of my eyepieces have undercuts... but all of my ES ones have tapers, as do my ES Focal Extenders. And since I sometimes use the extenders on my ES refractor for AP with my Olympus E-M1... I often wonder about the potential for induced tilt.

 

shrug.gif



#23 Starman1

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Posted 03 April 2020 - 06:52 PM

Thanks for that. How about this one?:

 

https://luntsolarsys...epiece-adapter/

 

...or this?:

 

https://www.bhphotov...25_adapter.html

The collets are good, but it looks like they both have undercuts--one conical, the other cylindrical.


Edited by Starman1, 03 April 2020 - 06:59 PM.


#24 Starman1

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Posted 03 April 2020 - 06:56 PM

A taper is not an undercut.  A tapered barrel is not as good as a smooth barrel, but is better than an undercut - and the taper is generally not an issue on a 2” OD barrel.  Certainly there can be seating/tipping issues with a 1.25” tapered barrel. Although I have never had an issue with a 1.25” taper either.   The taper on the WO roto-lock not been an issue with my star diagonal.  Like I said, It has eliminated my issues with undercuts completely.

 

The other thing about the WO version is the finger grips that make it very easy to twist.

 

But pick the one you like.  The important point is this style of adapter eliminates 1.25” eyepiece hang ups. 

A tapered barrel is actually a "conically tapered undercut".

It is an undercut because it is cut into the full O.D. of the barrel.

It is incompatible with brass split ring binders, and it is designed to work best with a single thumb screw tightening down on the conical taper.

When used in brass split ring binders, the brass ring distorts, sometime permanently.

Which is why Explore Scientific used spring steel instead of brass in their split-ring binders--so the ring would spring back and not stay distorted.

 

The only way the conical tapered undercut can tip sideways is if the small full-diameter section of barrel above the undercut is above the top of the focuser on the other side.

Otherwise, the thumbscrew pulls the eyepiece down, into the focuser, as it's tightened.


Edited by Starman1, 03 April 2020 - 06:58 PM.

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#25 B 26354

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Posted 03 April 2020 - 07:05 PM

collets are good, but it looks like they both have undercuts--one conical, the other cylindrical.

Thanks again. Kinda hard to tell, from the photos. I'll e-mail Lunt and Celestron, and ask for clarification... and post my findings here.  grin.gif

 

A cylindrical undercut would be perfectly acceptable for me. I'm currently in the process of adapting a 2" visual-back to my '77 C8, which I use for visual only. As such, I'd be leaving the 2"-to-1.25" adapter permanently inserted into the 2" visual-back.




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