39 replies to this topic

[f18dad]

 

 

And then we find that 2.5x GSO being 25% off….. 

 

 

20% - and not good!

 

But it's a good 2x barlow...

[davidgmd]

20% - and not good!

 

But it's a good 2x barlow...

  
Exactly. As long as you know what you’re getting before you buy it. One of the reasons I love this place.

[CHASLX200]

I love the 1.8 and 2.5x Circle NJ's i have.  I don't use them much unless the seeing is near dead still.

[Universe XY]

I'm confused on this TV 3X Barlow. I figure from the letter font it's an older barlow but is it a barlow with a missing ring or a barlow before they made them with rings?

 

It has an indentation as where a ring would go but not ring.

 

Is this going to be a functional problem?

 

I'm thinking it it was a barlow designed without a compression ring then it should n ot have that space for one.

 

It means the screw will have to screw in more????

 

Is this going to be a problem? It has threads on the bottom for a filter if that helps date it.

[Mike W]

Call Televue, they don't bite!

[Universe XY]

Call Televue, they don't bite!

Not used to having a responsive company. I have a feeling it's an old Televue Barlow but just concerned it's not a barlow with a missing compression band.

 

I guess I was hoping someone with a old 3X...Hey, I'll ask Jon. Think he had one...

[Mike W]

Oh it's old for sure.

[Universe XY]

It's a R not NJ so not the oldest & marked Japan on top of black barrel. Looks new old stock but there is a space for a compression band but no band.

Still it has a suction fit. An eye piece inserted kind of it drawn into it & tight so the screw should hold it. Seems centered.

 

Bigger than my Meade 2X 140 telenegative triplet modifier which I have really never used. It's so long. Do you need diagonal extenders?

 

I guess I'll try it on a 32mm & 24mm? would that bring it to about 11 & 8mm?

 

Maybe Tele Vue sells those brass bands? Wonder how they install?

 

 

space for ring

 

Someone said they called TeleVue & they have a end ring upgrade...Trying to find Tele Vue # or contact John Rhodes.

Edited by Universe XY, 17 April 2025 - 05:54 PM.

[Jon Isaacs]

Not used to having a responsive company. I have a feeling it's an old Televue Barlow but just concerned it's not a barlow with a missing compression band.

 

I guess I was hoping someone with a old 3X...Hey, I'll ask Jon. Think he had one...

 

I have a 2x TV Barlow but not a 3x.  People complain about undercuts but the real problem is the so called compression rings. As Don has pointed out, they are not compression rings, they only compress underneath the set screw,.  Their main role is to protect the eyepiece barrel from nicks.  The Aluminum set screw does that.  

 

I generally remove the brass ring and just use the set screw.  I have over 200 Nylon 10-32 thumbscrews. I bought a half pound of them at a surplus store. If you want one, I can put a couple in an envelope and send them to you.

 

My recommendation:  Do not replace the brass ring. They can be problematic when used with eyepieces with undercuts.  

 

Jon

[azure1961p]

I heard that the Powermates are better for imaging and TV Barlows better for visual.  Does that sound accurate?

 

Pete

[russell23]

I heard that the Powermates are better for imaging and TV Barlows better for visual. Does that sound accurate?

Pete

I really liked the 2.5x Powermate, but I found the 3x TV barlow, 2.4x Dakin Barlow,and 2.5x Siebert Telecentric barlow sharper in comparison for visual.

But that was my observations. Others will tell you the Powermate is sharper than barlows.

[Starman1]

I heard that the Powermates are better for imaging and TV Barlows better for visual. Does that sound accurate?

Pete

PowerMates solve a number of imaging problems, but they are excellent for visual use, too.
Compared to Barlows, they:
--do not lengthen eye relief, so are usable with long focal length eyepieces or long eye relief eyepieces.
--do not vignette due to improper placement relative to the eyepiece
--do not change magnification with eyepieces that have different focal plane locations within the eyepieces.
--do not change magnification with increasing distance from the eyepiece (except the 5x one).

[Universe XY]

I have a 2x TV Barlow but not a 3x.  People complain about undercuts but the real problem is the so called compression rings. As Don has pointed out, they are not compression rings, they only compress underneath the set screw,.  Their main role is to protect the eyepiece barrel from nicks.  The Aluminum set screw does that.  

 

I generally remove the brass ring and just use the set screw.  I have over 200 Nylon 10-32 thumbscrews. I bought a half pound of them at a surplus store. If you want one, I can put a couple in an envelope and send them to you.

 

My recommendation:  Do not replace the brass ring. They can be problematic when used with eyepieces with undercuts.  

 

Jon

 

I get what you are saying about the ring in some. It can catch & make it difficult to insert an ep if/when the brass ring gets out of round.

 

Still swimming in the barlow mystery.

 

Really can't see using them with heavy grenade ep's.

 

I'm trying it just to compare but can't see regular use with such a big heavy skyscraper.

 

My Barlow collection is growing but mostly unused.

 

Orion Shorty 2X

Meade triplet 140 2X (pretty light

Dakin 2.4X very light

TV 2.5X NJ

TV 3X

 

Will get back when I can compare the TV's

[Jon Isaacs]

PowerMates solve a number of imaging problems, but they are excellent for visual use, too.
Compared to Barlows, they:
--do not lengthen eye relief, so are usable with long focal length eyepieces or long eye relief eyepieces.
--do not vignette due to improper placement relative to the eyepiece
--do not change magnification with eyepieces that have different focal plane locations within the eyepieces.
--do not change magnification with increasing distance from the eyepiece (except the 5x one).

 

I use Barlows with medium and short focal length eyepieces.  The issues that Powermates solve generally do not apply.  On the other hand, the ability to increase the magnification by simply pulling the eyepiece back is rather useful.  

 

Our mutual friend Bruce (Astro-Master) has made a science of using the 17mm and 13mm Ethos with the 2x TV Big Barlow and the A-P Barlow with spacers to achieve a wide range of magnifications.  It works surprisingly well.  

 

Jon

[CHASLX200]

I'm confused on this TV 3X Barlow. I figure from the letter font it's an older barlow but is it a barlow with a missing ring or a barlow before they made them with rings?

 

It has an indentation as where a ring would go but not ring.

 

Is this going to be a functional problem?

 

I'm thinking it it was a barlow designed without a compression ring then it should n ot have that space for one.

 

It means the screw will have to screw in more????

 

Is this going to be a problem? It has threads on the bottom for a filter if that helps date it.

Televue 3X barlow.JPG

Televue 3X barlow no ring.JPG

Televue 3X barlow.JPG

Televue 3X barlow threads .JPG

Looks to be made in the early 90's.