Any drawback to using a barlow?

[MarkVIIIMarc]

I have read and agree a barlow lense makes more sense economically than buying another lense if you are looking for more magnification because the barlow effectively doubles the number of lenses you have.

Are there any drawbacks to using a barlow? I don't recall reading anything stating a 9mm on a 2x barlow is worse than a 4.5mm lens alone.  Is it in any way?

[Mak the Night]

A lot depends on the quality, if you are prepared to spend the money on TeleVue Barlows or similar you will get the best results. But modestly priced Barlows can perform well.

I've collected some, for various tasks and telescopes. It doesn't always pay to have too much glass in the light train though. I'd often rather use a longer focal length eyepiece combined with a Barlow as it usually allows a greater magnification with an eyepiece with a larger field stop and eye relief, making the viewing experience more enjoyable. Using a Barlow can give you a flexibility in magnification range. The only drawbacks are when poorer quality Barlows affect the image in a detrimental way and sometimes cause effects such as vignetting. Although a Barlow can often increase the eye relief of a short focal length eyepiece making it more tolerable.

Edited March 31, 2016 by Mak the Night

[Dave In Vermont]

A Barlow can be a wonderful addition! But a warning is in order: A low-quality Barlow can cause a dimming of the view through the eyepiece, and also cause a blurry image - vignetting. Which is why I always suggest one spring the $$$ and get the best Barlow (or PowerMate-type of apochromatic-lens) available. Such as the 2X or 3X Barlows from TeleVue®. There are other top-notch ones as well. A poor quality, cheap Barlow will only magify it's own defects and cause the user to leave the thing collecting dust - or ending up as a cat-toy. And top-end Barlows aren't really that much more $$$. And they have the advantage of being the last Barlow you'll ever buy - because in terms of the view, there is only going down in quality from the top!

I'll let someone else make additional suggestions of other top-end Barlows to consider.

This is my opinion - and I'm sticking to it!

Dave

[cotterless45]

Personally they're the last thing in the ep case that I'd reach for. The x2.5 Revelation one isn't all that bad. I use an old x2 Vixen triplet one with a Vixen Plossl on top. Gives a decent 5mm ep.

trouble is that most folks start out with basic ones and as Dave says, they don't do the job,

clear skies !

Nick.

[bomberbaz]

I use a Televue 2" 2x Powermate quite a lot when I am using my own 10" dob and it is brilliant. It is used on my Nikon (at 17 and 14 settings) and SW SWA 22mm (all 2" fitting) which gives me the additional optoins of 22mm, 8.5 and 7. 

I do not actually use the 22mm without the Powermate so the one Nikon eyepiece gives me 4 options, between the 2 though with the PM I have x71, x86, x109 (22mm), x141 & x171. I would point out the Nikon has a huge field of view and so I do not feel the need for anything inbetween and I think of the set up above as my main nebula and galaxy hunting setup.

These mean I really do not need any other eyepieces from the mid range right through to near maximum high power although I do have 3 other 1.25" fitting eyepieces for pushing the scope to its limit at 6,5 & 4mm. (x200, 240 & 300)

So its advantages for me are I can mainly use my favourite eyepiece (Nikon) for the majority of my viewing making it economical and just so much easier without any loss in light due to the high quality of the Powermate.

In case you wonder about my other glass its optional for use with the dob, does go into the focuser occasionally but is mainly for use in the ED100 refractor.

Hope this helps.

[brantuk]

Also don't forget that when you use any barlow of any quality, you are magnifying the seeing. So if it's humid or dusty or you have whispy high level cloud - you may end up just magnifying imperfections in the atmosphere. Same goes for high mag eyepieces even without a barlow in the light train.

[PeterCPC]

You get what you pay for as they say. Televues are great.

Peter

[Stu]

To clarify one point, Barlows and PowerMates are not identical. The Barlow varies it's magnifying factor depending upon distance from the focal plane, and also has the effect of pushing out the eye relief from the original spec of the eyepiece. This is useful if using a short focal length plossl or Ortho for instance, making it more comfortable, but can be difficult with longer focal lengths as the eye relief becomes too long, and makes it difficult to position your eye correctly.

Powermates do not affect the eye relief of the eyepiece so it really does just double the magnification. They are also far less variable in their magnifying factor depending upon distance from the focal plane ie either unaffected or just by a small amount depending on the PM being used.

A high quality Barlow or PM will not affect the view negatively, I nearly always use one with my zoom eyepiece to get it to the focal range I want for planetary viewing. A poor quality Barlow will have you thinking your scope is rubbish!! ?

[MAN or ASTROMAN]

I find my TAL x2 Barlow pretty useful with the f5 scopes. Much better than the SW basic one that was supplied with the ST80.

It cost around £35 when I bought it (2012),but I understand that they are increasingly harder to find these days (having said that ,saw one online the other day-here?, ABS? can't remember exactly).

[michael.h.f.wilkinson]

I have a couple of good tele-centric Barlows (TV PowerMates, Meade TeleXtenders and a Baader TZ-4 tele-centric optimized for H-alpha). I really only use them for imaging. Visually, I find them excellent, but changing magnification by inserting a Barlow always entails a few extra operations of capping and uncapping stuff, and more importantly refocusing. Especially for planetary views, having to change the position of focus (by a large amount) each time you switch to and from a Barlow is much less comfortable, and far slower than swapping (par-focal) eyepieces. 

If you are on a budget, this is of course less of a consideration.

[glowjet]

If you decide to invest in a Barlow, then make it one of good quality. One respectable source has quoted, "that a poor quality Barlow is better used as a door stop" TeleView insist that a good Barlow should, add nothing, or detract from, the field of view, however, quality products from the likes of this company will need extensions to the pocket, but there are other makes which give excellent results.

I am sure some of the membership will be able to provide you with some popular makes costs

[Alan64]

7 hours ago, MarkVIIIMarc said:

I have read and agree a barlow lense makes more sense economically than buying another lense if you are looking for more magnification because the barlow effectively doubles the number of lenses you have.

Are there any drawbacks to using a barlow? I don't recall reading anything stating a 9mm on a 2x barlow is worse than a 4.5mm lens alone.  Is it in any way?

Either one of these would be a great choice, and without the cost of a Tele Vue...

http://agenaastro.com/antares-1-25-2x-barlow-lens-twist-lock-adapter-t-thread-ub2stl.html

http://agenaastro.com/baader-q-barlow-bqb-2956185.html

Edited March 31, 2016 by Alan64

[MarkVIIIMarc]

Thanks again for much insight. 

I have two follow up questions.

Am I using google correctly and finding the PowerMates to be about $300?  or 3 to 6 times the cost of a Barlow?

My telescope is a Zumhell Z10.  They offer a 2" barlow for $50 something, or about 10 Jack n' Cokes lol.  Since Zumhell made my scope, do they make a reasonable barlow?

[Perseus_m45]

9 hours ago, cotterless45 said:

Personally they're the last thing in the ep case that I'd reach for. The x2.5 Revelation one isn't all that bad. I use an old x2 Vixen triplet one with a Vixen Plossl on top. Gives a decent 5mm ep.

trouble is that most folks start out with basic ones and as Dave says, they don't do the job,

clear skies !

Nick.

I'm with Nicko on this one here .I think the more glass the light has to go through the more degraded the image is . Simple physics . I will not use a Barlow on close doubles . In fact if my main intention is just to get the split I use eyepieces with as few elements of glass as I can get .Simply concentrating on the very center of the FOV .At this point I do not care what the edges of the image look like . But if I'm just enjoying some "old friends" and the surrounding star field I often use a 20mm Meade research grade and Televue 2x .Striking would be the word .

[Mak the Night]

1 hour ago, Perseus_m45 said:

I'm with Nicko on this one here .I think the more glass the light has to go through the more degraded the image is . Simple physics . I will not use a Barlow on close doubles . In fact if my main intention is just to get the split I use eyepieces with as few elements of glass as I can get .Simply concentrating on the very center of the FOV .At this point I do not care what the edges of the image look like . But if I'm just enjoying some "old friends" and the surrounding star field I often use a 20mm Meade research grade and Televue 2x .Striking would be the word .

I'll often elect to use a simpler Plossl or ortho' design over a Nagler or Panoptic for very similar reasons. I love my 24mm Pan but sometimes I find I am preferring my 25mm TV Plossl or 25mm Hutech ortho' on some targets; like M42 for instance. Likewise, I'll substitute a 15mm TV Plossl or 18mm AH ortho' occasionally for my 16mm T5 Nagler. I'm pretty sure it's because they have simpler 'less glass' designs and can seem to give a brighter image.

Having said that, for lunar observing, my Nagler T5 was almost always connected to my 2.5x Powermate when used in conjunction with my 102mm Mak (giving me about 203x). The ironical thing is that I believe Naglers have a form of integral Barlow element as part of their design.

[John]

22 minutes ago, Mak the Night said:

.... The ironical thing is that I believe Naglers have a form of integral Barlow element as part of their design.

Most wide angle and / or long eye relief eyepieces use a barlow or smyth type lens set in the eyepiece barrel.

 

 

[Physopto]

The only difference/downside  I can see if using a very good quality 2 or 3x convertor such as a Televue or Explore scientific.  Is that of the extra weight involved. Especially the 2" variety.

Derek

[Grotemobile]

This is what I have just bought. It is a 4 lens Barlow. Unscrew the end, & U can use it as a 1.5x .

http://www.telescopehouse.com/barlows/bresser-barlows/bresser-sa-barlow-2x-1-25-inch.hml

[Chris]

Revelation Barlows are very good and cheap. I'm back to basics with eyepieces at the moment, so I'm using a Rev Barlow with a bunch of cheap Plossls. I've been pleasantly surprised by the views so far, so consider myself a Barlow convert  

Edited March 31, 2016 by Chris Lock

[Mak the Night]

30 minutes ago, John said:

Most wide angle and / or long eye relief eyepieces use a barlow or smyth type lens set in the eyepiece barrel.

 

 

Yes, thanks, I was trying to remember 'Smyth type lenses'. It still fascinates me just how optically complex Naglers and similar are. I think I read how Al Nagler was influenced by WWII U-Boat periscope designs.

[Mak the Night]

19 minutes ago, Grotemobile said:

This is what I have just bought. It is a 4 lens Barlow. Unscrew the end, & U can use it as a 1.5x .

http://www.telescopehouse.com/barlows/bresser-barlows/bresser-sa-barlow-2x-1-25-inch.hml

That looks very nice.

[Mak the Night]

25 minutes ago, Physopto said:

The only difference/downside  I can see if using a very good quality 2 or 3x convertor such as a Televue or Explore scientific.  Is that of the extra weight involved. Especially the 2" variety.

Derek

This is the reason why I bought a couple of shorty apochromatic Barlows for my tabletop Mak. The TV's are too heavy.

[Perseus_m45]

2 hours ago, Mak the Night said:

I'll often elect to use a simpler Plossl or ortho' design over a Nagler or Panoptic for very similar reasons. I love my 24mm Pan but sometimes I find I am preferring my 25mm TV Plossl or 25mm Hutech ortho' on some targets; like M42 for instance. Likewise, I'll substitute a 15mm TV Plossl or 18mm AH ortho' occasionally for my 16mm T5 Nagler. I'm pretty sure it's because they have simpler 'less glass' designs and can seem to give a brighter image.

Having said that, for lunar observing, my Nagler T5 was almost always connected to my 2.5x Powermate when used in conjunction with my 102mm Mak (giving me about 203x). The ironical thing is that I believe Naglers have a form of integral Barlow element as part of their design.

In my very humble opinion its hard to beat a good plossl or an ortho' . Most are smallish and lightweight .

[Mak the Night]

3 hours ago, Perseus_m45 said:

In my very humble opinion its hard to beat a good plossl or an ortho' . Most are smallish and lightweight .

I've recently acquired a 90mm Mak with a tabletop Dob mount as a grab'n'go. Naturally it is quite a light scope, so eyepieces weighing in at half a kilo or more aren't really an option lol. I have a couple of reasonably light apochromatic Barlows (2x & 2.5x) for it as well. Oddly though, I tend to predominantly use it with one of the five eyepieces below sans Barlow. They range from an 18mm AH ortho' to an 8mm TV Plossl giving me magnifications of 55.5x, 66.6x, 91x, 100x and 125x all without a Barlow. I was viewing the Moon early this morning and all that was between me, the Moon and the eyepiece were the diagonal, the primary mirror, the meniscus lens, 10, 000 km of atmosphere and 392, 349 kilometres of interplanetary space!

Edited March 31, 2016 by Mak the Night

[Dave In Vermont]

An orthoscopic is my preffered planetary and other solar-system objects eyepieces. But if you need to wear glasses while observing, these may not be practical due to their short eye-relief. I also had an Orion-USA 'Shorty' Barlow - from which I removed the Barlow-lens from. This I use to screw into my eyepieces and/or zoom EP's for a boost in magnification by 1.5X or 1.6X - not sure which.

"If it t'aint broke - don't fix it!"

Dave