barlow quality

[iwols]

just wondered if anyone had comments on the different quality of 2x barlows,is there much difference especially for astrophotography thanks

[xvariablestarx]

Nice images.

 

[JamesF]

Some barlows are certainly considered to be better than others.  The Orion Shorty Plus and Celestron Ultima (actually the same thing IIRC) always seemed to be well-regarded though I think they're both out of production now and they don't seem to come up second hand very often.  I don't recall seeing much negative about the TeleVue 2x barlow either.  I found the Relevation 2.5x barlow to be good too.  I seem to recall some discussion that it may be the same as the Shorty Plus and Ultima, but I can't remember the outcome for certain.

James

[MarsG76]

You get what you pay for... Celestron Ultima and Televue 2X Barlow will give you the sharpest images.

 

[Guest]

Another plus for the Celestron Ultima. No noticeable degradation of the image to my view. I would not part with mine. Keep looking for a used one.

Tal 2x were said to be good. 

Put out a wanted ad. 

[RT65CB-SWL]

Following on from what @JamesF has said, I borrowed a Revelation 2.5x Barlow from a work colleague several years ago and found very good too. I use a Klee 2.8x and it is very good. TeleVue Barlow's & Powermate's are highly recommended. Below is part of an article from TeleVue HQ...

Powermate™ vs. Barlow
To understand the Powermate™, we must first understand the Barlow lens. Barlows amplify the power of a telescope. They can be considered "focal reducers" for eyepieces, or "focal extenders" for objectives. Terence Dickenson, in his Barlow test report in Sky and Telescope, July 1997, says: "Technology has erased the old objections. A modern Barlow will not degrade your telescope's optics. Anyone telling you otherwise is using outdated information. Moreover, the highly regarded Nagler eyepieces and their clones have built-in Barlows, ample evidence that the lens is not some detrimental intruder." Thanks, Terence, for laying the myth of the degrading Barlow to rest.

A high quality Barlow must be properly designed and manufactured in order to avoid compromising a telescope's color and spherical aberration corrections. The "invisibility" of Tele Vue's 2-element Barlows has been noted in test reports in the astronomy magazines. However, by the nature of its negative power lens, a Barlow will do more than just increase magnification, regardless of the number of elements.

The diverging rays leaving the Barlow result in moving the exit pupil further out, thereby extending the eye relief. In short to medium focal length eyepieces the change is not noticeable. However, in the case of long focal length eyepieces, the increase can be significant and not without performance consequences.

Vignetting can occur due to the altered ray path, when the eyepiece's lenses are not large enough in diameter to allow all the rays to make it through. Shorter Barlows, or ones with too much magnification, only exacerbate the problem because the ray path entering the eyepiece is steeper.

We had to go beyond the Barlow concept to achieve the goal of a compact, high power, fully corrected image amplifier. The Powermate™ consists of a negative doublet plus a positive "pupil-correcting" doublet. This 4-element system provides the magnifying function of a Barlow without its limitations by restoring the field rays back to their original direction, as if the Powermate™ were not there. The result is a pure magnification increase.

 

...and there's more... 

http://www.televue.com/engine/TV3b_page.asp?id=52&Tab=_back

http://www.televue.com/engine/TV3b_page.asp?id=53&Tab=_back

[iwols]

Any thoughts on thé baader hyperion ,2.25 barlow 

[david_taurus83]

41 minutes ago, iwols said:

Any thoughts on thé baader hyperion ,2.25 barlow 

I have this. I bought it along with my Baader Zoom eyepiece. Haven't used any other barlow so can't really compare. I only use it though when looking at Jupiter as it reduces the brightness a bit but apart from that I don't know if I'm a fan of barlows. Its also a screw in type. It's screws into the 1.25" thread on the bottom of the eyepiece.

[iwols]

35 minutes ago, david_taurus83 said:

I have this. I bought it along with my Baader Zoom eyepiece. Haven't used any other barlow so can't really compare. I only use it though when looking at Jupiter as it reduces the brightness a bit but apart from that I don't know if I'm a fan of barlows. Its also a screw in type. It's screws into the 1.25" thread on the bottom of the eyepiece.

Understand what your saying about barlows