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Eyepiece Safety Undercuts - a Bad Idea From the Start

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#201 turtle86

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Posted 16 February 2020 - 08:50 PM

I knew it was only a matter of time before someone blamed climate change.

 

The Carbon Devil strikes again.

 

wink.gif

 

:lol:



#202 ckwastro

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Posted 17 February 2020 - 08:11 AM

I don't experience snags in this adapter (it's sold under different names):

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

Notice also:

--the collet extends all the way to the opening

--the collet is quite long

--the bottom is threaded for 2" filters

--the adapter has smooth sides without an undercut.

Thanks Don, I’ll check out those adapters. 



#203 Mr. Mike

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Posted 17 February 2020 - 08:33 AM

All of my eyepieces with undercuts snag all the time. I’ve owned a lot of TV eyepieces over the years so I pretty much just expect them to hang up, especially in the binoviewer collets, so it’s automatic to expect it. Have never dropped one, but if I had my choice I’d rather have smooth barrels. Don’t really care for the undercuts at all. 

Yeah - I do have this happen from time to time and while its annoying it never ruins my session or anything.  Ive learned to just really loosen the compression screws on the diagonals/other gear and that seems to work.  I do wish these undercuts were gone though.  Id prefer a smooth barrel for easier insertion/extraction.


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#204 Jon Isaacs

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Posted 17 February 2020 - 09:56 AM

I'm trying to figure out the same thing as you from my side of it.   Why are some people saying they never have problems with undercut catches?  I can't seem to avoid the problem with squared undercuts.

 

 

In the interest of further understanding:

 

- How often does an eyepiece hangup? 

 

- How long does it take to resolve the issue? 

 

- How do resolve the issue?

 

I believe that for those experiencing this as an issue, it's real. Whether it's due to differences in equipment, differences in technique or something else, it's worth figuring out.

 

Jeff mentions weight, I'm using TeleVues heaviest eyepieces without issues. Don mentions the horizontal focuser, my 22 inch has a horizontal focuser, I don't seem to have issues with that either.

 

Jon


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#205 25585

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Posted 17 February 2020 - 11:40 AM

If thumbscrews all had flat tips so captive, it would be so easy, just loosen until no turning left. Then you can tell its clear without the darned thing coming out. Also larger width heads are good.

 

AFA collars, some cheaper ones are copper, and distort easier than brass or steel, tgey are more affected by temperature as well. Plastic/synthetic collars can be OK but depends on the plastic, they also are affected by temperature.

 

But none of the designs are made by those who use telescopes, as for most anything. CN people being inventive and imaginative, what are your ideas for an eyepiece holder that makes for easy insert and extraction, yet helps prevent an expensive eyepiece from falling out accidentally, either from scratch or modification of what is on offer at present? 

 

Vixen & Takahashi used to have screw on eyepieces, as did SLR camera lenses to bodies once. Now cameras have bayonet fitting lenses, perhaps there is an alternative for eyepieces?



#206 Jon Isaacs

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Posted 17 February 2020 - 01:18 PM

If thumbscrews all had flat tips so captive, it would be so easy, just loosen until no turning left. Then you can tell its clear without the darned thing coming out. Also larger width heads are good.

 

AFA collars, some cheaper ones are copper, and distort easier than brass or steel, tgey are more affected by temperature as well. Plastic/synthetic collars can be OK but depends on the plastic, they also are affected by temperature.

 

But none of the designs are made by those who use telescopes, as for most anything. CN people being inventive and imaginative, what are your ideas for an eyepiece holder that makes for easy insert and extraction, yet helps prevent an expensive eyepiece from falling out accidentally, either from scratch or modification of what is on offer at present? 

 

Vixen & Takahashi used to have screw on eyepieces, as did SLR camera lenses to bodies once. Now cameras have bayonet fitting lenses, perhaps there is an alternative for eyepieces?

 

My experiences:

 

The pre-compression ring TeleVue adapters and bits I have owned use captive 10-32 aluminum thumb screws. My NP-101 has a compression ring and has a captive thumbscrew. The Everbrite diagonal and adapter have compression rings and do not have captive screws, the diagonal itself has a long threaded piece, it takes 14 complete turns to remove the thumscrew. The adapter itself requires 6 complete turns to be removed, less than 1 turn to free the eyepiece.

 

The flattened head can eventually wear out and become loose. Removing it can be tricky, I replace them with nylon thumbscrews.

 

Regarding designers who use telescopes.. Al Nagler is a life long amateur astronomer, he's been involved over 70 years. He was 45 years old when the first TeleVue eyepiece was sold. My experiences are that TeleVue eyepieces work nicely with TeleVue adapters, Focusers, diagonals etc. Others may have issues. I attribute that to the fact that Al and others at TeleVue are amateur astronomers who use the stuff they make.

 

Jon



#207 russell23

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Posted 17 February 2020 - 03:48 PM

In the interest of further understanding:

 

- How often does an eyepiece hangup? 

 

- How long does it take to resolve the issue? 

 

- How do resolve the issue?

 

I believe that for those experiencing this as an issue, it's real. Whether it's due to differences in equipment, differences in technique or something else, it's worth figuring out.

 

Jeff mentions weight, I'm using TeleVues heaviest eyepieces without issues. Don mentions the horizontal focuser, my 22 inch has a horizontal focuser, I don't seem to have issues with that either.

 

Jon

I've never tabulated statistics during observing but with my current lineup of eyepieces the bigger problem than the undercut is the insertion from catching on the groove for the compression ring.  By catching I mean the insertion is completely stopped.   That happens probably ~ 1/3 to 1/2 the time with certain eyepieces   I resolve it by lifting the eyepiece back out and trying again.  Sometimes it takes 3 tries.   It can take a few seconds depending upon how many tries to get it right.

 

As I said before this insertion catching is not an issue with the Pentax XF which bevels the last 3mm of the barrel.  However, the XF has the square undercut so that one catches when extracting. 

 

None of this ruins an observing session, but it is a nuisance that has potential solutions.  That is why it keeps coming up in discussions.

 

I have a Williams Optics roto-lock en-route so I am looking forward to giving that a try my next observing session. 


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#208 Jon Isaacs

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Posted 18 February 2020 - 10:07 AM

I've never tabulated statistics during observing but with my current lineup of eyepieces the bigger problem than the undercut is the insertion from catching on the groove for the compression ring.  By catching I mean the insertion is completely stopped.   That happens probably ~ 1/3 to 1/2 the time with certain eyepieces   I resolve it by lifting the eyepiece back out and trying again.  Sometimes it takes 3 tries.   It can take a few seconds depending upon how many tries to get it right.

 

 

For comparison, I spend about an hour with my 120 Eon last night, it has a 2 inch non compression ring Everbrite with a GSO compression ring adapter.  I used my TMB Planetary's, Meade SWA's, a 12mm Paradigm, a 4.8 Nagler (smooth barrel). The adapter has an undercut, the 2 inch eyepiece did not.

 

For me, everything slipped in and came back out without any issues.

 

Jon



#209 Mike Spooner

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Posted 18 February 2020 - 11:04 AM

The undercuts and tapers really bug me (hasn't slowed down my eyepiece buying so go figure). 

It's more annoying on my 1 1/4" eyepieces - especially the small, slippery, high dollar ones.

It got bad enough I fixed it.

 

Clamprings would often push the little lip upwards and tilt the eyepiece in the adapter as would set screws that were not quite down far enough. Tapers? Really? Straight in screws will tilt the eyepiece if the diameters are too different ( one of my optically favorite eyepieces is almost .025" undersize!). 

 

So I made the adapter in the photo. Being angled, the nylon screw exerts downward and radial clamping pressure. If it catches an undercut lip, it is the lower one (desirable) and the line of force against a taper extends to the opposite side of the full cylinder below the taper on those eyepieces so it clamps solidly against the adapter, thus no tilt. The downward force also pulls the eyepiece against the top of the adapter thus helping to minimize tilt yet again.

 

I haven't made a 2" focuser tube yet but I generally have a better grip on those larger, heavier eyepieces. 

 

You're welcome. smile.gif

 

Mike Spooner

 

image.jpeg


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#210 ascii

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Posted 18 February 2020 - 12:14 PM

The undercuts and tapers really bug me (hasn't slowed down my eyepiece buying so go figure). 

It's more annoying on my 1 1/4" eyepieces - especially the small, slippery, high dollar ones.

It got bad enough I fixed it.

 

Clamprings would often push the little lip upwards and tilt the eyepiece in the adapter as would set screws that were not quite down far enough. Tapers? Really? Straight in screws will tilt the eyepiece if the diameters are too different ( one of my optically favorite eyepieces is almost .025" undersize!). 

 

So I made the adapter in the photo. Being angled, the nylon screw exerts downward and radial clamping pressure. If it catches an undercut lip, it is the lower one (desirable) and the line of force against a taper extends to the opposite side of the full cylinder below the taper on those eyepieces so it clamps solidly against the adapter, thus no tilt. The downward force also pulls the eyepiece against the top of the adapter thus helping to minimize tilt yet again.

 

I haven't made a 2" focuser tube yet but I generally have a better grip on those larger, heavier eyepieces. 

 

You're welcome. smile.gif

 

Mike Spooner

 

attachicon.gifimage.jpeg

You should try selling those.  We're never going to get eyepiece manufacturers to end this idiocy, but 2" to 1.25" adapters with nylon or nylon tipped screws, without clamp rings or channels that snag would be a godsend.  A bevel on the top inside edge would be good too, since it would reduce insertion snags where the top edge of the eyepiece undercut hits the top of the adapter as it goes in.


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#211 csrlice12

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Posted 18 February 2020 - 12:54 PM

Patent it....though it may be too late.



#212 Starman1

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Posted 18 February 2020 - 03:17 PM

You should try selling those.  We're never going to get eyepiece manufacturers to end this idiocy, but 2" to 1.25" adapters with nylon or nylon tipped screws, without clamp rings or channels that snag would be a godsend.  A bevel on the top inside edge would be good too, since it would reduce insertion snags where the top edge of the eyepiece undercut hits the top of the adapter as it goes in.

Beveling the top lip?  BAD idea.

Many/most eyepieces with undercut grooves have a very short section of full diameter barrel above the undercut.

It is essential this short section of full diameter press against the other side of the bore when the thumbscrew is tightened.

Ergo, the entry point of the bore should be a square lip, and not beveled.

 

This is an issue with some twist lock designs as well, where the collet does not extend all the way to the opening, so does not clamp down on the small section

of full diameter above the undercut.

 

As for TeleVue working with TeleVue, try tightening a 24mm Panoptic in a TeleVue adapter--it tips.

 

Mike is wrong about one thing: the conically tapered undercut works fine with thumb screws and does not tip--just as long as the small full diameter section above the taper

is pressed against a non-beveled entry to the bore on the other side.  In fact, tightening the thumbscrew pulls the eyepiece down into the adapter into full flat contact at the eyepiece's shoulder.

If it tips, the thumbscrew might be hitting on the lip of the undercut--always a possibility. 


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#213 Chucky

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Posted 18 February 2020 - 03:25 PM

Maybe I'm the only one......but I could care less about undercuts or no undercuts.  Never had an issue or problem either way.  I just deal with it and observe.  


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#214 Jon Isaacs

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Posted 18 February 2020 - 03:37 PM

Patent it....though it may be too late.

 

It has similarities to the Howie Glatter Parallaizer. 

 

https://youtu.be/sd3stObWI_I

 

Jon


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#215 Mike Spooner

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Posted 18 February 2020 - 07:05 PM

 

 

Mike is wrong about one thing: the conically tapered undercut works fine with thumb screws and does not tip--just as long as the small full diameter section above the taper

is pressed against a non-beveled entry to the bore on the other side.  In fact, tightening the thumbscrew pulls the eyepiece down into the adapter into full flat contact at the eyepiece's shoulder.

If it tips, the thumbscrew might be hitting on the lip of the undercut--always a possibility. 

Just my luck to have an adapter with the screw right at the top and it does tilt the eyepiece but it's probably an unfortunate combination of the really undersized ep and looking closer I think the adapter likely had the screw added so not a real issue with the typical commercial adapter. 



#216 25585

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Posted 18 February 2020 - 08:36 PM

Perhaps this Baader accessory is a solution of sorts https://www.firstlig...-extension.html



#217 carver2011

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Posted 18 February 2020 - 09:27 PM

Maybe I'm the only one......but I could care less about undercuts or no undercuts.  Never had an issue or problem either way.  I just deal with it and observe.  

I agree. Much to do about nothing. I use a new Celestron 2”Twist lock visual back diagonal. No screw to mess with, hold tight, releases easily. Much of the issue with grooves is turning the screws out enough to not snag on the grooves. Two screws, double the issue. Going back and forth until they clear the groove. All the time worrying, not too much, or the screw ends up lost in the grass. Twist lock solves much of this. I feel much of the problem isn’t the grooves, it’s the small screws. A very awkward inefficient way of securing an eyepiece. I think the grooves are a possible insurance against dropping a $600 eyepiece on the ground.  JMHO

Ed


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#218 russell23

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Posted 21 February 2020 - 10:14 PM

I just spent a few hours observing and used my newly purchased Williams Optics roto-lock adapter.  What a difference!  No catching on insertion or extraction for any eyepiece I used.   The mechanism is super-smooth and can be loosened with a light touch.   Eyepieces are locked in tight.   The undercut is not a problem with this style adapter.


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#219 James Ball

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Posted 22 February 2020 - 01:00 PM

What about designing a spring steel(or polymer) ring that would slide on the barrel of the eyepiece with the undercut and snap on place sorta like the compression rings on a piston in an engine? It might even be able to be 3D printed.

 

Just slip them on the eyepiece and no more undercut.  May need to design a few sizes for the various depths of the groove in different eyepieces, or make a few thicknesses and stack if the cut is deeper on one eyepiece than another.  If you get it to where the groove is only fractions of a mm less than the outer diameter of the barrel then the compression band problem should go away and there would be very minimal hangs with just a setscrew.


Edited by James Ball, 22 February 2020 - 01:01 PM.


#220 CounterWeight

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Posted 24 February 2020 - 09:48 PM

That a good idea, something like a slip ring washer that could be easily slipped into and out of the groove.  Only issue I see is that it would need to be a very good fit (both inner and outer diameter) or your going to have other issues?  I've just been using metal HVAC tape and getting it pretty close.




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