Barlow or not?

[TBRHussaR]

Does a Barlow decrease the contrast of the image? Is it better to just own more eyepieces?

[Zeta Reticulan]

24 minutes ago, TBRHussaR said:

Does a Barlow decrease the contrast of the image? Is it better to just own more eyepieces?

Depends on the Barlow quality. Most modern inexpensive achromatic Barlows are fine. Many eyepieces actually have integral Barlow type tele-negative (Smyth) lenses anyway. Some are amplifiers, such as the Tele Vue Powermates and increase magnification without much vignetting or increase of eye relief.

The simpler 'shorty' type are useful in diagonals or when weight is a factor.

Obviously any addition to the light train will have some impact.

It isn't always that noticeable. Sometimes chromatic aberration can be a problem. The GSO 3x (below, middle) is basically a spectrometer in use. The other GSO Barlows are fine. Maybe a little bit of CA in the 5x.

The distance the Barlow element is from the field lens governs the magnification factor and any possible vignetting issues.

Many Barlows are generic and sold under different names. The Vixen Deluxe below is made in Japan. The Vixen shorty next to it is sold under a variety of brand names and is made in the PRC.

The Takahashi Barlow below is deigned to be used primarily before the diagonal.

I have a few Barlows. As a whole I don't notice any real contrast decrease when using them. A lot depends on the eyepiece used in conjunction with them, prevailing conditions, the target, and the scope used.

[Franklin]

Wow! You're the Barlow man!

I've got the Vixen Deluxe 2x and it doesn't introduce any trouble to the view at all, I think it's a very good barlow but the snout is quite long. I did try the Vixen shorty 2x but I think it's more of a budget option (same as the Celestron 2x T2 Barlow that comes with their Plossl eyepiece set.) It was ok when used with longer fl eyepieces but with shorter fl eyepieces ca and vignetting became apparent.

[Zeta Reticulan]

1 minute ago, Franklin said:

Wow! You're the Barlow man!

I've got the Vixen Deluxe 2x and it doesn't introduce any trouble to the view at all, I think it's a very good barlow but the snout is quite long. I did try the Vixen shorty 2x but I think it's more of a budget option (same as the Celestron 2x T2 Barlow that comes with their Plossl eyepiece set.) It was ok when used with longer fl eyepieces but with shorter fl eyepieces ca and vignetting became apparent.

And those aren't all my Barlows lol! The Vixen Deluxe is superb, as good as the TV 2x. It was designed for shorter focal ratio scopes I believe. It achieves focus in my f/6, 150mm GSO Newtonian where my TV 3x and 2x won't. The 'Vixen' shorty was probably made by Barsta. All shorty achromatic Barlows can have CA/vignetting problems at times IME. 

I forgot this one. lol (I have even more)

[Franklin]

I think the Vixen Deluxe 2x was maybe intended for use straight through or before the diagonal (2.6x) like the Takahashi due to the length of the snout. You could damage a mirror or prism if you were not aware of this.

[Franklin]

1 hour ago, TBRHussaR said:

Does a Barlow decrease the contrast of the image? Is it better to just own more eyepieces?

Sorry for muscling in on your thread.

Back in the day, Barlows received a bad reputation, much like Zoom eyepieces did and the reason was that "less glass is better". 

Modern designs and coatings have superseded this view and the Barlows and Zooms of today are mainly very good quality items. I've used a Baader 2.25x Barlow with their MKIV Zoom and the combo was, to my eye, actually better than using the Zoom alone, even though both setups produced the same magnification. So I think the old adage of "less glass is better" is a little outdated nowadays. Just look at the number of elements in all those fancy wide angle £500+ eyepieces out there. 

Modern Barlows are great and can be used to obtain higher magnifications without using really short focal length eyepieces which helps with eye relief and general comfort whilst observing. I'd go for a 3 element over a 2 element Barlow if getting one.

[Zeta Reticulan]

13 minutes ago, Franklin said:

I think the Vixen Deluxe 2x was maybe intended for use straight through or before the diagonal (2.6x) like the Takahashi due to the length of the snout. You could damage a mirror or prism if you were not aware of this.

Yeah, it's long. It's an entire element and actually threads off from the housing. The Tak' is a bit weird. It needs an extension tube on most Tak' f/7.5 refractors. 

 

Or my 80ED DS Pro. The SvBony Barlow housing (sans element) used in this picture as an extension was not successful. It achieved focus alright but had vibration return issues. The Tak' Barlow can be used conventionally in a 2" diagonal. I believe it was designed for the Tak' flip mirror. However, if used in a 1.25" diagonal its narrow field lens housing can make contact with a prism surface.

[Don Pensack]

A Barlow can reduce astigmatism in an eyepiece by making the light cone entering the eyepiece slower.

Many inexpensive eyepieces that are not good below f/8 clean right up when used with a Barlow.

Also, if your eyepiece eye reliefs get tighter with shorter focal lengths, barlowing a longer focal length works quite well.

It's the main reason Siebert Optics offers long focal length monocentric eyepieces to be used with high power barlows to yield short focal lengths with comfortable eye reliefs.

[Louis D]

3 hours ago, TBRHussaR said:

Is it better to just own more eyepieces?

To answer the second question, it depends on your budget and eyepiece case size.  If I'm going to use a Barlow during an observing session, I'll just leave it in the focuser while switching eyepieces because fumbling with a third item in the dark is not fun when you only have two hands.

In general, the matched Smyth lens in long eye relief, high power eyepieces works better than trying to Barlow a lower power eyepiece to the same power.  However, it costs more to have a bunch of high quality eyepieces in your eyepiece case.

[Zeta Reticulan]

Well, this Barlowed eyepiece has impressed me.

The (SvBony) element basically turns it into a 5.8mm EP. I certainly see no loss of anything in use.

[Mr Spock]

Modern Barlows don't affect the contrast much and as has been said, provide some benefits. My Circle-T orthoscopics seem to gain an edge in both contrast and sharpness when used with a Barlow. I use the nosepiece from a Meade 140 Apo (shown below) attached to a Svbony 70mm extension tube to give x2.1. The Meade on its own measures at x2.4 but doesn't have a compression ring.

The 2" Barlow I have is surprisingly good too, though I don't use it much.

 

 

[Guest]

This is the one i use with my 2 inch eyepieces.  For grins i dropped a 14mm in it and turned it loose on the moon.  I have to say the image was very good with no loss of contrast at all.  

[Zermelo]

I was about to start a separate thread for a question on barlows, but seeing that this one is quite similar ...

I've upgraded my eyepieces since starting out (now into the three-figure range) but I still have my original Barlows: a Celestron Omni x2 and a Baader Classic Q x2.25, both being 1.25", 2-element, short designs.

I'm wondering if it's worth spending more on a new Barlow, given that it would probably see as much action as any one of my EPs. I'm visual only.

There are a few factors to weigh up:

- Barlow or telecentric?
- if Barlow, 2 element vs 3 element vs ED
- if Barlow, long or short?
- x2 or x3 (or something else)
- 1.25" or 2" (I only have a couple of 2" EPs, but I notice that some manufacturers don't make all the mags in both barrel sizes)

And then the choice between manufacturers, and the clones of manufacturers.

I have to say that I don't notice any CA or vignetting with my existing Barlows - not saying it's not there, but I'm not aware of it. The one thing that I do notice is a significant increase in scattered light when I add a Barlow. Since one of my main interests is splitting tight doubles, I sometimes find that the scatter impairs the success, by reducing the contrast or obscuring fainter components completely.

Does anyone have any comments on the factors above, specifically with regard to scattered light? Or recommend specific models? To what extent does it depend on the specific eyepiece being used with a particular Barlow?

I'm not looking to spend Powermate prices, but would consider something up to £120ish (and I'd consider second hand, or a cheaper clone, if available).

[Deadlake]

I bought a baradv a couple of months ago, but only recently have made use of it for planetary usage with either BV or mono viewing.

The Barlow is attached ahead of the diagonal with an extender to gain focus. Magnification will be around x3.5 turning a F6 I have into F21

I suspect from initial usage that it makes the 10 mm UFF I have perform very well giving very high contrast on the moon.

Saturn is a little too low to draw any conclusions.

Would I sell my TOE's or HR's. I need more usage to draw any conclusions, however it does make for a long stack.

Using with a APM zoom would be very good for moon viewing and away around this.

Also work in progress is use with a BV, however I suspect that will increase contrast as well.

For cheaper alternatives the APM Coma Correcting 2.7x Barlow, around £150 new is meant to be good and only beaten by the Baader Zeiss or FCC Barlows.

I have the Baradv as it's more accommodating for BV usage.

 

[Don Pensack]

3 hours ago, Zermelo said:

I was about to start a separate thread for a question on barlows, but seeing that this one is quite similar ...

I've upgraded my eyepieces since starting out (now into the three-figure range) but I still have my original Barlows: a Celestron Omni x2 and a Baader Classic Q x2.25, both being 1.25", 2-element, short designs.

I'm wondering if it's worth spending more on a new Barlow, given that it would probably see as much action as any one of my EPs. I'm visual only.

There are a few factors to weigh up:

- Barlow or telecentric?

If you are barlowing mid power eyepieces to yield high power eyepieces, I don't think it matters.  If the eyepieces have large field stops, though, the telecentric ones affect the image a lot less.

- if Barlow, 2 element vs 3 element vs ED

3 elements are only used to reduce the Barlow's focal length and make it shorter.  3 elements are not optically superior to 2.

ED elements serve the function of controlling chromatic aberration in a very short focal length Barlow.  With normal Barlows like a TeleVue or Baader, ED glass is not important.

- if Barlow, long or short?

Longer Barlows have some advantages, but are not popular with users of scopes with star diagonals.  They work fine in reflectors.

- x2 or x3 (or something else)

That depends.  But using a Barlow with more than 2X often puts the eyepieces into such a high power range that seeing conditions don't allow the use.

I think a 2X Barlow is usually the most likely to be used often; maybe 2.25.

- 1.25" or 2" (I only have a couple of 2" EPs, but I notice that some manufacturers don't make all the mags in both barrel sizes)

Since typically only low power eyepieces are 2", and barlowing 2" eyepieces merely produces medium powers, where you already have eyepieces, a 2" Barlow

is not often the best choice.  For most observers, the 1.25" Barlow makes the most sense unless your medium power eyepieces happen to be 2".  That's not all than common, though.

 

And then the choice between manufacturers, and the clones of manufacturers.

I've seen some very nice Barlows from TeleVue, Celestron, Meade, Baader, Nikon, APM over the years.  There are a lot of fine choices.

In telecentrics, I favor TeleVue.  In telenegatives, I favor the Baader VIP (it worked better with a 7mm eyepiece than a separate 3.5mm).

 

I have to say that I don't notice any CA or vignetting with my existing Barlows - not saying it's not there, but I'm not aware of it. The one thing that I do notice is a significant increase in scattered light when I add a Barlow. Since one of my main interests is splitting tight doubles, I sometimes find that the scatter impairs the success, by reducing the contrast or obscuring fainter components completely.

This will point your to higher end Barlows that are better baffled and have better coatings.

 

Does anyone have any comments on the factors above, specifically with regard to scattered light? Or recommend specific models? To what extent does it depend on the specific eyepiece being used with a particular Barlow?

For control of scattered light, stay away from Explore Scientific, Meade, Celestron, GSO, and many others.  You are looking at TeleVue, Baader VIP, Nikon, maybe Zeiss.

 

I'm not looking to spend Powermate prices, but would consider something up to £120ish (and I'd consider second hand, or a cheaper clone, if available).

Cheap and good control of scattered light are not compatible parameters.  £120 and down means you are looking at cheap Barlows, and you will not find the lens polish, baffling, or color control

at that price range that you are looking for.

 

 

I reply above, in between your lines.

Edited August 9, 2022 by Don Pensack

[Zeta Reticulan]

3 hours ago, Zermelo said:

I was about to start a separate thread for a question on barlows, but seeing that this one is quite similar ...

I've upgraded my eyepieces since starting out (now into the three-figure range) but I still have my original Barlows: a Celestron Omni x2 and a Baader Classic Q x2.25, both being 1.25", 2-element, short designs.

I'm wondering if it's worth spending more on a new Barlow, given that it would probably see as much action as any one of my EPs. I'm visual only.

There are a few factors to weigh up:

- Barlow or telecentric?
- if Barlow, 2 element vs 3 element vs ED
- if Barlow, long or short?
- x2 or x3 (or something else)
- 1.25" or 2" (I only have a couple of 2" EPs, but I notice that some manufacturers don't make all the mags in both barrel sizes)

And then the choice between manufacturers, and the clones of manufacturers.

I have to say that I don't notice any CA or vignetting with my existing Barlows - not saying it's not there, but I'm not aware of it. The one thing that I do notice is a significant increase in scattered light when I add a Barlow. Since one of my main interests is splitting tight doubles, I sometimes find that the scatter impairs the success, by reducing the contrast or obscuring fainter components completely.

Does anyone have any comments on the factors above, specifically with regard to scattered light? Or recommend specific models? To what extent does it depend on the specific eyepiece being used with a particular Barlow?

I'm not looking to spend Powermate prices, but would consider something up to £120ish (and I'd consider second hand, or a cheaper clone, if available).

These are reasonably priced. I have the 3x.

I'm strictly visual as well. Admittedly it has an undercut. I haven't had any problems with extraction or insertion though. For a 3x amplifier I find it relatively light and compact, with a short barrel, which works well in a diagonal. Oddly I like it for splitting doubles.