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Modern TV Plossl without the Undercut?

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#1 BillP

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Posted 21 February 2015 - 05:12 PM

Just noticed on AMart (http://www.astromart...ified_id=879871) a modern (circle-R) 32mm TV Plossl without the undercut defect!!  I thought the only smooth barreled TV Plossls were the old smooth sided housing ones?   Anyway...it looks good!!


Edited by BillP, 21 February 2015 - 05:13 PM.


#2 swix

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Posted 21 February 2015 - 06:27 PM

I have one without the undercut.  It was purchased from Company 7

or Pocono Mountain Optics in the late 1990's. They are real...

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Edited by swix, 23 February 2015 - 09:28 AM.


#3 junomike

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Posted 21 February 2015 - 06:52 PM

Just noticed on AMart (http://www.astromart...ified_id=879871) a modern (circle-R) 32mm TV Plossl without the undercut defect!!  I thought the only smooth barreled TV Plossls were the old smooth sided housing ones?   Anyway...it looks good!!

Is it possible someone swapped out a "smoothie" barrel for the undercut one? (not sure if they are compatible).

 

Mike



#4 John Anthony

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Posted 22 February 2015 - 12:10 PM

 All of the TV Plossl's on the TV website show the undercut, I have only the 8-25mm, maybe at one time the dreaded undercut wasn't there with the more modern one.  A while back when the subject of the dreaded undercut was brought up I thought whats the big deal??  Now that I have been using a full set of Ortho's without the undercut and I get the TV Plossl's out with the undercut I kind of understand why most wouldn't like the undercut.  But for the most part I don't get to bothered by it but can say I prefer no undercut.  I also noticed the undercut doesn't seem to bother me as much on larger eyepieces like the Delos, more of a hassle handling the smaller TV Plossl's. 


Edited by John Anthony, 22 February 2015 - 12:12 PM.


#5 John Huntley

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Posted 22 February 2015 - 04:37 PM

I have a very recent TV 32mm plossl which has an undercut but the lower edge has a gradual taper to it as shown in the example from the Tele Vue website:

 

http://www.televue.c....0#.VOpLbyyCC7Q

 

All my other TV plossls have the undercut with the upper and lower edges cut to the same profile. It looks like the tapered one is being used on the 32mm, 25mm and 20mm focal lengths currently.

 

I've had a 32mm TV plossl without an undercut as well but that was some years ago.


Edited by John Huntley, 22 February 2015 - 04:40 PM.


#6 Brian Carter

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Posted 22 February 2015 - 08:01 PM

Do people hate the undercut because it gets caught on focuser retaining rings when you're pulling them out? That's why I hate them.

#7 star drop

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Posted 22 February 2015 - 08:40 PM

Do people hate the undercut because it gets caught on focuser retaining rings when you're pulling them out? That's why I hate them.

Yes.



#8 junomike

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Posted 22 February 2015 - 09:34 PM

I have a very recent TV 32mm plossl which has an undercut but the lower edge has a gradual taper to it as shown in the example from the Tele Vue website:

 

http://www.televue.c....0#.VOpLbyyCC7Q

 

All my other TV plossls have the undercut with the upper and lower edges cut to the same profile. It looks like the tapered one is being used on the 32mm, 25mm and 20mm focal lengths currently.

 

I've had a 32mm TV plossl without an undercut as well but that was some years ago.

This new taper-barrel design aids in eliminating the "catch on exit" problem but some eyepiece collets still won't fully grasp them (APM 100 Binoculars).

 

Mike



#9 tonyt

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Posted 23 February 2015 - 03:13 AM

The undercuts can be a nuisance in binoviewers - the straight barrels always sit square. I just bought some 18mm Fujiyama orthos to replace the 20mm TV plossls which keep tilting off square in my Binotron.  



#10 BillP

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Posted 23 February 2015 - 09:53 AM

This new taper-barrel design aids in eliminating the "catch on exit" problem but some eyepiece collets still won't fully grasp them (APM 100 Binoculars).

 

Mike

 

 

Instead of "aids in eliminating", I would say instead maybe "potentially lessens".  Reason being is that I had this new style and in one of my compression ring holders it was getting stuck all the time.  So still can be problematic.

 

FWIW, for EPs with the undercut defect, I've had them get caught both for insertion and extraction.  It makes eyepiece compares a royal p.i.t.a. 

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#11 Peter Besenbruch

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Posted 23 February 2015 - 01:12 PM

Do people hate the undercut because it gets caught on focuser retaining rings when you're pulling them out? That's why I hate them.

 

Me, too. In addition, those of us who use compression ring clamps on the focuser or diagonal often have trouble getting a decent lock on the eyepiece. Eyepieces also have trouble going in square. The eyepiece barrel undercut is one of the worst inventions in modern astronomy. The person who invented it should be ashamed of an infliction that makes people's lives a little more miserable.



#12 BillP

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Posted 23 February 2015 - 01:58 PM

Peter...great idea!!  Let's hunt down which manufacturer was first with the dreaded undercut defect!  Once we discover which...we can start a letter writing campaign :grin:



#13 junomike

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Posted 23 February 2015 - 03:29 PM

 

This new taper-barrel design aids in eliminating the "catch on exit" problem but some eyepiece collets still won't fully grasp them (APM 100 Binoculars).

 

Mike

 

 

Instead of "aids in eliminating", I would say instead maybe "potentially lessens".  Reason being is that I had this new style and in one of my compression ring holders it was getting stuck all the time.  So still can be problematic.

 

FWIW, for EPs with the undercut defect, I've had them get caught both for insertion and extraction.  It makes eyepiece compares a royal p.i.t.a. 

 

Bill you might be right as I usually use my Antares Twist Lock adapters for mono viewing and my TV Binoues have "splines" which the undercut doesn't affect.

My 15/19/24 Pans were an issue in my APM 100 Semi Apo's but a layer of duct tape (to fill the gap) fixed than issue also.

 

Mike



#14 BillP

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Posted 23 February 2015 - 03:36 PM

FWIW, I see that back in 2003 TV Plossls had undercuts.  Back in 2001 some 2" Celestron EPs were showing undercuts, but not the 1.25" models.  So looks like around the turn of the millennia to 2000 that they came about.  Perhaps a byproduct of the Year 2000 fixes that were going on.  :lol:



#15 junomike

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Posted 23 February 2015 - 03:41 PM

FWIW, I see that back in 2003 TV Plossls had undercuts.  Back in 2001 some 2" Celestron EPs were showing undercuts, but not the 1.25" models.  So looks like around the turn of the millennia to 2000 that they came about.  Perhaps a byproduct of the Year 2000 fixes that were going on.  :lol:

 

So what you're saying Bill, is that you'd prefer TeleVue undercut their competition and not the barrels? :thinking:

 

Mike



#16 csrlice12

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Posted 23 February 2015 - 04:11 PM

If it's a materials cost, I'll pay the extra $.01 in costs to fill in those undercuts.......



#17 tomcody

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Posted 23 February 2015 - 04:32 PM

Do people hate the undercut because it gets caught on focuser retaining rings when you're pulling them out? That's why I hate them.

Or if they have a compression diagonal like my Takahashi 1.25" prism, which will not close far enough to clamp an undercut eyepiece like the Televues and just lets them wobble about. I have to use eyepiece spacer rings to move the undercut above the clamping point, or, as I am doing, replacing all my Televue eyepieces with Takahashi LE's  !!!!!

( a consumer move which is good for Takahashi, bad for Televue. )

Rex

PS And yes I could just use my Baader Ziess prism diagonal ( which clamps anything! ) but I just hate dealing with those undercuts.



#18 Peter Besenbruch

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Posted 23 February 2015 - 08:32 PM

My 15/19/24 Pans were an issue in my APM 100 Semi Apo's but a layer of duct tape (to fill the gap) fixed than issue also.

 

From the Episcopal Book of Common Prayer...

 

"Look with pity, O heavenly Father, upon the people in this land who live with injustice, terror, disease, death and undercuts as their constant companions."

 

From elsewhere in the Book of Common Prayer...

 

"Let us give thanks to God our Father for all his gifts so
freely bestowed upon us.

 

"For the beauty and wonder of your creation, in earth and sky and sea,
We thank you, Lord.

 

"For eyepieces without undercuts,

We thank you, Lord.

 

"For tape to fill in undercuts,

We thank you, Lord."

 

Those Episcopalians were on to something.



#19 catboat

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Posted 24 February 2015 - 02:56 AM

 

My 15/19/24 Pans were an issue in my APM 100 Semi Apo's but a layer of duct tape (to fill the gap) fixed than issue also.

 

. . .

 

"For eyepieces without undercuts,

We thank you, Lord.

 

"For tape to fill in undercuts,

We thank you, Lord."

 

Those Episcopalians were on to something.

 

Perhaps.  But those worthy reformists broke with their traditions of parsimony, prudence, and practicality (the three P’s) when they condoned the proliferation of compression rings, which are as irritating as undercuts and which commonly display the additional vice of inducing eyepiece tilt.  If undercuts are destined for damnation, compression rings should accompany them across the Styx.     :gramps:


Edited by catboat, 24 February 2015 - 08:59 AM.


#20 BillP

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Posted 24 February 2015 - 09:04 AM

So what you're saying Bill, is that you'd prefer TeleVue undercut their competition and not the barrels? :thinking:

 

 

 

:lol:  ... Exactly!



#21 Peter Besenbruch

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Posted 24 February 2015 - 05:20 PM

 

Those Episcopalians were on to something.

 

Perhaps.  But those worthy reformists broke with their traditions of parsimony, prudence, and practicality (the three P’s) when they condoned the proliferation of compression rings, which are as irritating as undercuts and which commonly display the additional vice of inducing eyepiece tilt.  If undercuts are destined for damnation, compression rings should accompany them across the Styx.     :gramps:

 

But compression rings have the advantage of being non marring. Yes, you get screws with non marring tips, but to tighten them enough, you have to mess up the non-marring tip.

 

Consider compression rings to be the Quakers of the telescope world, non-violent, non-marring, and always a bit at odds with the rest of eyepiece society.


Edited by Peter Besenbruch, 24 February 2015 - 05:27 PM.


#22 csrlice12

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Posted 24 February 2015 - 06:22 PM

and the oatmeal boxes make great dew shields...........



#23 BillP

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Posted 25 February 2015 - 01:17 PM

 

 

But compression rings have the advantage of being non marring.

 

 

I'm having no issues with the nylon set screws I used to replace the metal ones in my non-compression ring gear.  They work like a charm.  And if they ever get messed up for any reason, a penny gets you a new one.



#24 Peter Besenbruch

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Posted 25 February 2015 - 02:56 PM

 

But compression rings have the advantage of being non marring.

 

I'm having no issues with the nylon set screws I used to replace the metal ones in my non-compression ring gear.  They work like a charm.  And if they ever get messed up for any reason, a penny gets you a new one.

 

They are not that cheap when you factor in the time, gas, and wear and tear to replace them.

 

For myself, I have ho issue using set screws in a diagonal. Where I run into trouble is using them ON a diagonal, particularly if I want to rotate the diagonal sideways. With what I would call a moderately heavy eyepiece (think Baader zoom) I find the set screws not up to snuff.

 

My current arrangement is a Baader Clicklock holding an Astrotech compression ring 2" to 1.25" adapter. The combination works. A previous adapter with a nylon tipped set screw would not tighten enough, but instead mashed the nylon screw.

 

The diagonal is the 1.25" Takahashi that I picked up for $90. The issue I have is with the Takahashi compression ring. It works on Baader eyepiece undercuts, but not with Explore Scientific, or the BST 58° eyepieces. I try to defeat the undercuts with tape.



#25 BillP

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Posted 25 February 2015 - 04:57 PM

I have a number of accessories that have dual set screws.  While these are also compression ring items, they use very thick and large screws so provide a super strong lock.  So a dual set screw using robustly sized screws out of nylon should be good enough for just about anything within reason.  Sure maybe a imaging setup or a Barlow plus 31T5 would stress things, but for those outliers they should have to purchase special holders and not subject everyone to that nightmare. 




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