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Praise for the 3x TV barlow

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#1 russell23

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Posted 12 January 2015 - 02:12 PM

Barlows (both regular and telecentric) seem to be one of those tools that observers either are really comfortable having in their case or hate having in their case.  I fall in the category of people that like having a barlow but I have no critiques for people that prefer not to use barlows. 

 

The primary reasons I like to use barlows are:

 

1.  They improve eyepiece edge performance.

2.  They allow high magnifications to be achieved with longer FL, longer eye relief eyepieces. 

 

The one thing I require of a barlow though is that its performance be essentially transparent with no negative impacts on image quality.  In that regard I think the 3x TV is perhaps the most underrated barlow out there.  I have had two of these 3x TV barlows and both were optically outstanding having zero negative impacts on eyepiece performance.  I would rank this barlow a very close 2nd to the 2" 2.4x Vernonscope Dakin barlow.   I suspect the 3x magnification factor scares a lot of people away from this barlow, but it is outstanding with 15-24mm 1.25" eyepieces and worth considering for anyone who likes using barlows.   I use it extensively with my 24mm and 20mm ES68's. 

 

Here is how I rank the barlows I have used over the years:

 

Optically flawless:

1. 2" 2.4x Vernonscope Dakin barlow

2. 1.25" 3x TV barlow

3. 1.25" 2.4x Vernonscope Dakin barlow

4. 2" 2.5x Siebert Telecentric barlow

5. 1.25" 1.5x Siebert barlow

5b. 2" 2.0x Siebert Telecentric barlow

 

Optically excellent but not flawless:

 

6. 1.25" 2.0x ES focal extender

6b. 1.25" 3.0x ES focal extender

7. 1.25" 2.5x TV Powermate

7b. 1.25" 5.0x TV Powermate

8. 2.0" 2.0x ES focal extender

 

Optically good but also overrated:

 

9. 1.25" 2.0x TV barlow

10. 2.0" AP Barcon

11. 2.0" TV Big Barlow

12. 2.0" 1.6x Antares barlow 

 

Save up for something better:

 

13. 1.25" 1.8x TV barlow

14. 1.25" 3.0x Antares barlow

15. 2.0" 2.0x GSO barlow

16. 1.25" 2.0x Orion Shorty-plus barlow

17. 1.25" 2.0x Celestron Silvertop barlow

 

I know some people will disagree with my classifications of the various barlows, but that is how I rate them for my purposes and what my advice would be if you are looking to pick up a barlow.  Obviously there are barlows I have not tried.  However, the thing I see is that the 3x TV barlow is absolutely one of the best out there - only edged out by the 2" Vernonscope Dakin barlow.  The only ranking on my list that I might like to re-investigate is the 1.25" 2.0x TV barlow.   The sample I had did not impress me and I would like to check out another sample sometime just to verify.  What I saw with the 2.0x TV barlow was that it did not improve the edge performance of eyepieces and possibly introduced some EOFB.

 

Dave


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#2 BillP

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Posted 12 January 2015 - 03:09 PM

One day I need to try the Dakin.



#3 bgi

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Posted 12 January 2015 - 06:58 PM

Thank you for taking the time to share your experience with us.  I'm sure it took many nights over a long time to come up with that summary.

 

I'm curious why the TV 2x didn't impress.  Admittedly, I've only used it with Delos 12, 10, 8 where it was definitely transparent.  No edge clean up needed - just clear scale-up that didn't detract in any way that I could detect.  Now you have me curious.  I'll give it a try with some eyepieces that need a little clean-up help.  :)

 

I had a Dakin 2.4x for a short time. Unfortunately, it was very old and the lens cement had begun to separate, so it went back.


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#4 Peter Besenbruch

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Posted 13 January 2015 - 01:43 PM

One day I need to try the Dakin.

 

And report back on it. They aren't cheap.



#5 SteveG

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Posted 13 January 2015 - 01:50 PM

Excellent review - you've tested a lot of barlows!

 

I've been experimenting with 3x barlows for about 2 years now. My criteria is a little different though; I'm looking for the sharpest view on axis, and nothing else.

 

I use my 3x barlows with Brandons, on planets only for this testing. I'm really going to ramp up the testing for the coming Jupiter season. My location is not good for this type of testing, which is why I've been at it for so long.

 

So far, I feel I get the best image with the Orion TriMag, followed by the TV 3x. All of them are so close that I have not been able to pick a clear winner. One thing I've discovered is that some of my 3x barlows have different magnification increases, and one of them only magnifies at about 2.7x. The TV probably wins for build quality.



#6 bluesteel

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Posted 13 January 2015 - 01:51 PM

Thank you for taking the time to post this! I think your observations are in line with mine, although I have only looked through a couple of the ones you have listed. People have praised the TV 2x barlows, either in the 1.25" or 2" format, but when I tried the 2" format out, I was very underwhelmed with its performance. Made things much softer, even though the power was not extraordinarily high for my scope, using Delos eyepieces with it. It made a sharp Delos 14mm as soft, if not a touch softer, than a TMB Planetary 6mm, which was very surprising. Verifying that the seeing was steady with a 3.5mm Delos solidified my observations, and back the barlow went.

 

russell23, I see you ranked the 2" format of the Vernonscope Dakin barlow higher than the 1.25" format. I take it there was a detectible difference between the two? I have been contemplating picking one of those up eventually, and your input would be greatly appreciated! :D


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#7 russell23

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Posted 13 January 2015 - 02:41 PM

One day I need to try the Dakin.

Worth a try - the 2" Dakin is great with a refractor.  I can't speak about its performance and ability to focus with a reflector.  With a refractor I need to put it in front of the star diagonal to reach focus.  I mainly use it for lunar/planetary observations because I don't swap the barlow in and out when I'm observing those targets.  When I observe deep sky the swapping in and out is less convenient. It is the sharpest barlow for lunar observations I have tried.

 

Dave



#8 russell23

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Posted 13 January 2015 - 02:43 PM

Thank you for taking the time to share your experience with us.  I'm sure it took many nights over a long time to come up with that summary.

 

I'm curious why the TV 2x didn't impress.  Admittedly, I've only used it with Delos 12, 10, 8 where it was definitely transparent.  No edge clean up needed - just clear scale-up that didn't detract in any way that I could detect.  Now you have me curious.  I'll give it a try with some eyepieces that need a little clean-up help.   :)

 

I had a Dakin 2.4x for a short time. Unfortunately, it was very old and the lens cement had begun to separate, so it went back.

 

Mainly with the 2x barlow I felt as if edge performance was negatively impacted - not to the extent that the "look for something better" barlows were affected, but certainly noticeable.  Sharpness at the edge seemed to suffer and there was some mild EOFB introduced with some eyepieces.  But like I said - I'd like to grab another 2x TV barlow to double check that since the 3x is so excellent.

 

Dave



#9 russell23

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Posted 13 January 2015 - 02:48 PM

Thank you for taking the time to post this! I think your observations are in line with mine, although I have only looked through a couple of the ones you have listed. People have praised the TV 2x barlows, either in the 1.25" or 2" format, but when I tried the 2" format out, I was very underwhelmed with its performance. Made things much softer, even though the power was not extraordinarily high for my scope, using Delos eyepieces with it. It made a sharp Delos 14mm as soft, if not a touch softer, than a TMB Planetary 6mm, which was very surprising. Verifying that the seeing was steady with a 3.5mm Delos solidified my observations, and back the barlow went.

 

russell23, I see you ranked the 2" format of the Vernonscope Dakin barlow higher than the 1.25" format. I take it there was a detectible difference between the two? I have been contemplating picking one of those up eventually, and your input would be greatly appreciated! :D

 

I agree about the 2" 2x TV barlow - very underwhelming and seriously overrated if my sample was typical for that barlow.  Definitely made things softer.

 

As for the Dakin's, I briefly had the 2" and 1.25" at the same time.  The 2" definitely seemed sharper to me near the edges of the field and slightly so at the center.  Don Yeier told me that when he had the 2" Dakin designed the optician did not just scale up the 1.25" Dakin but also refined it although I do not know in what ways.  So the 2" Dakin should be the better barlow overall and that seems to be the case.  But that is another comparison I would like to do again. 

 

To me the biggest problem with the 1.25" Dakin is the mechanicals.  The 2" Dakin has a nice compression ring.  The 1.25" has a set screw that is easily lost and the 1.25" eyepiece fit is sometimes very tight so that there is some air pressure resistance as the eyepiece is pushed in.  The new owners of Vernonscope should add a compression ring to the 1.25" Dakin.

 

The 3x TV barlow has a very smooth compression ring.  Nice feel on that one - smoother than the ES focal extenders.

 

Dave

 

Dave



#10 BillP

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Posted 13 January 2015 - 02:50 PM

 

Mainly with the 2x barlow I felt as if edge performance was negatively impacted - not to the extent that the "look for something better" barlows were affected, but certainly noticeable.  Sharpness at the edge seemed to suffer ....

 

 

I have noted this with mine as well. 



#11 paul m schofield

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Posted 13 January 2015 - 03:23 PM

Over the years I have bought and sold a Meade 2-3x barlow, TV 2.5x barlow, TV 2.5x Powermate, UO 2.8x Klee, TV 3x (brand new),  TV 2x barlow, and a TV 3x (bought used). I should have kept the brand new TV 3x because it was the best of the bunch. The Klee was very close. The used TV 3x wasn't quite as good and the TV 2x never seemed as sharp as my original TV 3x. Hindsight is a wonderful thing. I finally found one that matches the quality view: an early model made-in-Japan Orion Tri-mag. It's pretty much a TV 3x clone although the set screw isn't as heavy duty. Superb optical quality though. 



#12 russell23

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Posted 14 January 2015 - 09:37 AM

 

 

Mainly with the 2x barlow I felt as if edge performance was negatively impacted - not to the extent that the "look for something better" barlows were affected, but certainly noticeable.  Sharpness at the edge seemed to suffer ....

 

 

I have noted this with mine as well. 

 

 

Well that is reassuring for me.  I've bought the 1.6x Antares barlow three times and each time I was less satisfied than the previous time.  I guess I won't bother picking up another 2x TV barlow.  Just about every time I give an eyepiece/barlow that I sold for performance reasons a 2nd chance, my original decision to sell the first sample gets confirmed.  When I get another sample of an eyepiece/barlow that I sold for monetary reasons my regrets for having sold the first sample are also confirmed ... as is the case with my not too long ago aquired 3x TV barlow - the 2nd one I have owned.  Never should have sold that 1st 3x TV barlow - although the compression ring screw is a lot smoother on this one.

 

The performance difference between the 3x and 2x TV barlows is an additional reason I heap praise on the 3x TV barlow.  I'm not one of those people that thinks everything TV puts out is great.  But when they nail it - they really nail it.  They nailed it with the 3x TV barlow.  People that have not been impressed with the 2x TV barlow should be aware that the 3x TV barlow is a better barlow (much better IMO but I know not everyone that has used both agrees so as always YMMV).

 

Dave



#13 BillP

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Posted 14 January 2015 - 12:05 PM

I'm not sure if the lens cell in the TV 2x and 3x are really any different.  They may be the same cell in different length housings to achieve the additional magnification.  If this is so, then perhaps why the 2x does not perform as well.  I had the TV 3x as well and felt like you it was superior.

 

As example, I have an APM 2.7x ED Barlow (best Barlow for the price IMO).  If I put this in another housing so the magnification is 2x, then it shows a lot of lateral color and the off-axis not so good.  About as low as it can go and operate cleanly is 2.2x.  So it has a definite operating range for best performance, like all Barlows.  So this could be a reason if the same lens cell is used for both Barlows...but I don't know this is the case or not.



#14 russell23

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Posted 14 January 2015 - 01:45 PM

I'm not sure if the lens cell in the TV 2x and 3x are really any different.  They may be the same cell in different length housings to achieve the additional magnification.  If this is so, then perhaps why the 2x does not perform as well.  I had the TV 3x as well and felt like you it was superior.

 

As example, I have an APM 2.7x ED Barlow (best Barlow for the price IMO).  If I put this in another housing so the magnification is 2x, then it shows a lot of lateral color and the off-axis not so good.  About as low as it can go and operate cleanly is 2.2x.  So it has a definite operating range for best performance, like all Barlows.  So this could be a reason if the same lens cell is used for both Barlows...but I don't know this is the case or not.

 

I see that with the 2" Dakin barlow sometimes when used with extension tubes.  At 2.4x it is great with every eyepiece all the way to the edge - unless there is vignetting.  I've found that if I add extension tubes not only will it increase the magnification, but it will also reduce or eliminate the vignetting.   But with some eyepieces with the extension tube the edge performance improvement starts to reverse and sharpness is lost near the edges.

 

But I thought I read here one time that the 3x and 2x TV barlow lenses could be swapped to the barrel of the other for additional magnification factors different from 2x and 3x - which would mean it is not just the same lense in a different tube ... but I'm not positive I'm remembering reading that correcly.

 

Dave



#15 Peter Besenbruch

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Posted 14 January 2015 - 03:16 PM

 

 

 

Mainly with the 2x barlow I felt as if edge performance was negatively impacted - not to the extent that the "look for something better" barlows were affected, but certainly noticeable.  Sharpness at the edge seemed to suffer ....

 

 

I have noted this with mine as well. 

 

... Just about every time I give an eyepiece/barlow that I sold for performance reasons a 2nd chance, my original decision to sell the first sample gets confirmed.

 

... The performance difference between the 3x and 2x TV barlows is an additional reason I heap praise on the 3x TV barlow.  I'm not one of those people that thinks everything TV puts out is great.  But when they nail it - they really nail it.  They nailed it with the 3x TV barlow.

 

That's good to know. I have had three Televue Barlows. I had both the old 1.8x and 2.5x. The 2.5x was simply not sharp. The 1.8x was, but dimmed the image more than other Barlows. For planetary work that was less of an issue than with deepsky work. Had this thread been around a few weeks ago, I would have considered the Televue 3x.

 

The Televue Big Barlow was decent, though it showed a bit of vignetting with longer Panoptics and Televue Plössls (I owned the 32mm). Combined with the interface lens (effectively making it a telecentric Barlow), it performed better. Even better was the Celestron Ultima 2x shorty. It performed well with all 1.25" eyepieces, but for some reason wouldn't work with two inchers. ;) I recently acquired an Explore Scientific 3x telecentric Barlow. I agree with the OP; it's a very nice performer, especially for the price I paid for it.

 

I had also looked at Antares Barlows. Can you elaborate on what you didn't like?



#16 BillP

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Posted 14 January 2015 - 03:42 PM

The Televue Big Barlow was decent, though it showed a bit of vignetting with longer Panoptics and Televue Plössls (I owned the 32mm).

 

 

FYI, that's not an issue with the Barlow, but with the eyepieces.  The Pans and the TV Plossls because of their design vignette with a conventional Barlow, and why TV recommends a Powermate for those.


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#17 russell23

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Posted 14 January 2015 - 04:36 PM

 

 

 

 

Mainly with the 2x barlow I felt as if edge performance was negatively impacted - not to the extent that the "look for something better" barlows were affected, but certainly noticeable.  Sharpness at the edge seemed to suffer ....

 

 

I have noted this with mine as well. 

 

... Just about every time I give an eyepiece/barlow that I sold for performance reasons a 2nd chance, my original decision to sell the first sample gets confirmed.

 

... The performance difference between the 3x and 2x TV barlows is an additional reason I heap praise on the 3x TV barlow.  I'm not one of those people that thinks everything TV puts out is great.  But when they nail it - they really nail it.  They nailed it with the 3x TV barlow.

 

That's good to know. I have had three Televue Barlows. I had both the old 1.8x and 2.5x. The 2.5x was simply not sharp. The 1.8x was, but dimmed the image more than other Barlows. For planetary work that was less of an issue than with deepsky work. Had this thread been around a few weeks ago, I would have considered the Televue 3x.

 

The Televue Big Barlow was decent, though it showed a bit of vignetting with longer Panoptics and Televue Plössls (I owned the 32mm). Combined with the interface lens (effectively making it a telecentric Barlow), it performed better. Even better was the Celestron Ultima 2x shorty. It performed well with all 1.25" eyepieces, but for some reason wouldn't work with two inchers. ;) I recently acquired an Explore Scientific 3x telecentric Barlow. I agree with the OP; it's a very nice performer, especially for the price I paid for it.

 

I had also looked at Antares Barlows. Can you elaborate on what you didn't like?

 

 

I had a similar reaction to the TV 1.8x barlow - seemed to dim the image beyond what would be expected for the increased magnification.  TV coatings have definitely improved.

 

The Antares barlows for me just lack the transparency and sharpness - and that gets worse near the edges.  The 1.6x was decent and the 3x was ok, but both barlows negatively impacted the edge performance introducing some loss of sharpness and some EOFB.  And in the central field I could just tell the barlow was there whereas with a good barlow, you don't even notice its there other than the magnification change. 

 

Regarding the 3x ES focal extender.  I'm a real big fan of both the 2x and the 3x FE.  My only - and I mean only - issue with them is that for lunar observations they have introduced some scattered light that brightens the sky from the edge of the Moon to the field stop.  This is not seen with the 2" Dakin barlow or 3x TV barlow.  With my 495 LP filter on my achromats this scattered light takes on a brownish cast.  I have a 2x ES FE so when I get my SW120ED back from skywatcher I will see how the ES FE works with an APO.  Maybe it will be different.  For deep sky I have no issues with the FE - which is why I rank them where I do.

 

I do think in general the ES optics probably do not control scatter as well as premium eyepieces.  One thing I have noticed is that when I combine the 24mm and 20mm ES68's with the 2x ES FE I can see more scattered light or a less hi def sky background.  When I combine the ES68's with the 3x TV barlow the image seems more hi def.  When I combine my 32mm Brandon or the TV Pans (this past fall) with the ES FE the image seems more hi def.  So my thinking is that the ES optics have some scattered light and combining the ES FE with the ES eyepieces makes that more obvious.  Combining the ES with a premium barlow or the ES barlow with a premium eyepieces seems to limit the detectability of this effect.

 

Dave


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#18 Peter Besenbruch

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Posted 14 January 2015 - 05:01 PM

 

The Televue Big Barlow was decent, though it showed a bit of vignetting with longer Panoptics and Televue Plössls (I owned the 32mm).

 

FYI, that's not an issue with the Barlow, but with the eyepieces.  The Pans and the TV Plossls because of their design vignette with a conventional Barlow, and why TV recommends a Powermate for those.

 

Yes, that's true, but perhaps you can refresh my memory here. When Televue first came out with the Big Barlow, Astrophysics also sold a 2" Barlow. I seem to remember that both Astrophysics and various users claiming that the Astrophysics didn't not vignette, and needed no additional lenses. No claims were made that the Astrophysics was a telecentric Barlow. Do you know anything about this?


Edited by Peter Besenbruch, 14 January 2015 - 05:04 PM.


#19 bgi

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Posted 14 January 2015 - 05:09 PM

 

 

Mainly with the 2x barlow I felt as if edge performance was negatively impacted - not to the extent that the "look for something better" barlows were affected, but certainly noticeable.  Sharpness at the edge seemed to suffer ....

 

 

I have noted this with mine as well. 

 

 

I wonder if this impact is lessened or eliminated entirely when barlowing shorter FL eyepieces.  Any experience?  I'm putting this on my to-do list.  I've only closely examined the performance of the TV 2X with Delos 12, 10, 8, for which the 2X was specifically purchased.  I could have missed edge degradation.



#20 John Rhodes

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Posted 15 January 2015 - 12:22 PM

Group,

 There are some comments that the "2x never seemed as sharp as the 3x".

Also, Bill P. speculates that the 2x and 3x may be be the same cell in different length housings which is "perhaps why the 2x does not perform as well."
 
I asked Al to clarify:
 
" The 2x and 3x are independent designs, but both have the same on-axis performance:
Analyzed with an f/4.5 Parabola, the spot sizes compared to the airy disc were identical, with RMS less than 60% of the Airy Disc for d,f,c wavelengths combined.
 
Off-axis performance will vary, mainly because of the f/# difference of 2x compared to 3x, and the interactions with eyepieces and scopes, but center field performance should be similar. "
 

--


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#21 ibase

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Posted 15 January 2015 - 12:43 PM

Agree with John, the impression with my TV 2x and 3x barlows is that they're both equally sharp on-axis and won't hesitate to recommend the TV 2x barlow, it's good. Just 2 cents. 

 

TV_PowermateBarlow-2_zpsa4d033df.jpg

L-R: TV Powermate 2.5x, Barlow 2x, 3x

 

Best,


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#22 Scanning4Comets

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Posted 15 January 2015 - 02:07 PM

 

Thank you for taking the time to share your experience with us.  I'm sure it took many nights over a long time to come up with that summary.

 

I'm curious why the TV 2x didn't impress.  Admittedly, I've only used it with Delos 12, 10, 8 where it was definitely transparent.  No edge clean up needed - just clear scale-up that didn't detract in any way that I could detect.  Now you have me curious.  I'll give it a try with some eyepieces that need a little clean-up help.   :)

 

I had a Dakin 2.4x for a short time. Unfortunately, it was very old and the lens cement had begun to separate, so it went back.

 

Mainly with the 2x barlow I felt as if edge performance was negatively impacted - not to the extent that the "look for something better" barlows were affected, but certainly noticeable.  Sharpness at the edge seemed to suffer and there was some mild EOFB introduced with some eyepieces.  But like I said - I'd like to grab another 2x TV barlow to double check that since the 3x is so excellent.

 

Dave

 

Not IME.

 

Only longer FL eyepieces suffer from EOFB, which is really vignetting in my 2x TV barlow.


Edited by Scanning4Comets, 15 January 2015 - 02:08 PM.


#23 russell23

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Posted 15 January 2015 - 03:01 PM

 

 

Thank you for taking the time to share your experience with us.  I'm sure it took many nights over a long time to come up with that summary.

 

I'm curious why the TV 2x didn't impress.  Admittedly, I've only used it with Delos 12, 10, 8 where it was definitely transparent.  No edge clean up needed - just clear scale-up that didn't detract in any way that I could detect.  Now you have me curious.  I'll give it a try with some eyepieces that need a little clean-up help.   :)

 

I had a Dakin 2.4x for a short time. Unfortunately, it was very old and the lens cement had begun to separate, so it went back.

 

Mainly with the 2x barlow I felt as if edge performance was negatively impacted - not to the extent that the "look for something better" barlows were affected, but certainly noticeable.  Sharpness at the edge seemed to suffer and there was some mild EOFB introduced with some eyepieces.  But like I said - I'd like to grab another 2x TV barlow to double check that since the 3x is so excellent.

 

Dave

 

Not IME.

 

Only longer FL eyepieces suffer from EOFB, which is really vignetting in my 2x TV barlow.

 

That is not correct.  EOFB is not just in long FL eyepieces.  The worst case I've seen was in a 13mm Olivon70 while the 22mm Olivon had much less.  The 27mm Pan and 28mm ES68 have none.

 

EOFB is not vignetting either.  I'm not sure we are looking for the same phenomenon when we talk about EOFB.  I know we agree that our scopes are different so that could be a factor.  I sometimes wonder if the comain your scope masks the detectability of EOFB

 

Dave



#24 SteveG

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Posted 15 January 2015 - 03:42 PM

Over the years I have bought and sold a Meade 2-3x barlow, TV 2.5x barlow, TV 2.5x Powermate, UO 2.8x Klee, TV 3x (brand new),  TV 2x barlow, and a TV 3x (bought used). I should have kept the brand new TV 3x because it was the best of the bunch. The Klee was very close. The used TV 3x wasn't quite as good and the TV 2x never seemed as sharp as my original TV 3x. Hindsight is a wonderful thing. I finally found one that matches the quality view: an early model made-in-Japan Orion Tri-mag. It's pretty much a TV 3x clone although the set screw isn't as heavy duty. Superb optical quality though. 

Me too. And I bought mine used, I think it was $35. The TriMag is a sleeper!


  • paul m schofield likes this

#25 BillP

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Posted 15 January 2015 - 03:54 PM

John - Thanks for the clarification.  FWIW, I think when folks say their experience is that the 3x is sharper than the 2x, I doubt it between the two against each other and probably more that the 2x compared to similar magnification Barlows of other brands and the 3x compared to similar magnification Barlows of other brands. 

 

Peter - I personally do not recall discussions that the AP BARCON did not vignette with stated EPs.


Edited by BillP, 15 January 2015 - 03:57 PM.



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