Klee 2.8 Barlow

[dweller25]

Hello,

Does anyone have experience of a Klee 2.8 barlow ??

I currently use a Tal x3 Barlow which is great for the money but I am happy to spend a little more money on the Klee if it is sharper.

Any feedback would be appreciated.

[Merlin66]

I have an use both the x2.2 and the x2.8 Klee Barlow.

For me they are very good, and I prefer them to any other's I have for visual work.

For CCD I use them on the SM60 for solar Ha imaging... no complaints....they compare very well against the AE x4.0 and the TV x2.5

[Talitha]

I've been using a Klee 2.8 (visual only) for a number of years and am very pleased with its clarity and sharpness.

[dweller25]

Thanks for the feedback.

Very positive responses - I will buy one.

Best regards.

[Merlin66]

The Klee Barlows ( and the Pretoria 28mm eyepiece) were originally designed in the 80's to give "improved performance" with fast ie f4 newtonians, but have proved to be a very good all round piece of kit!!

[KaStern_Former_Member]

Hello dweller25,

I own both 2,8x and 2,2x Klee Barlows and use zhem with my 200/1200mm and 112/450mm Newts.

I like esspecially the 2,8x very much. It gives sharp and contrasty views.

I can confirm that it was designed by Heinz Klee to compensate for the off-axis coma of Newtonians.

Since it is a short barlow with high mag it will move the exit pupil out.

How much depends on the eyepiece focal length.

The longer the fl the farer the exit pupil is moved out.

I like the 2,8x Klee with my eyepieces from 18mm to 8mm focal length.

Clear skies, Karsten

[dweller25]

Wow, these certainly sound good.

Thanks for all the responses.

[KaStern_Former_Member]

Hello dweller25,

I just recognize that you have these scopes:

Takahashi TSA102S F8 refractor.

Celestron C9.25 F10 SCT.

Are you sure that you need a 3x or 2.8x barlow? Your scopes are f/10 and f/8

and you could reach high magnification even without any barlow.

Another thing to consider is the off-axis coma compensation of the Klee barlow.

It does this by adding coma of the opposite sign to the off-axis coma of a parabolic mirror.

The faster the mirror, the stroger the resulting coma and the stroger the compensation

the Klee Barlow does.

Your C 9,25 has off-axis coma too. It is significantly stronger than the off-axis coma

of an f/10 Mirror. So the klee will only compensate for a part of it.

Your Takahashi TSA 102 (congrats to this fine scope!) does not have off-axis coma.

If you use the Klee Barlow with the TSA you induce off-axis coma as strong as in a

102/800mm parabolic mirror.

I guess you will not see it unless you search for it. And the eyepieces play a roll too.

On-axis the Klee will give you crisp views with your Tak. But you may consider to use

a simple high quality orthoscopic eyepiece without any barlow at all.

Clear skies, Karsten

[dweller25]

Hello Karsten,

These are excellent points.

The Klee is to be used with the Takahashi.

I am a planetary observer and find around x200 is fine with the Tak. I am currently using Orthos but I wear glasses and the eye relief is not too good.

I want to draw at the eyepiece so my plan is to use a good quality Barlow with a 12mm Ortho giving x190 or 48D, that should give me around 10mm eye relief and allow me to wear my glasses.

I am currently using a x3 Tal barlow which is ok but wondered if the Klee would be a little sharper. As you say the Klee was designed for fast newtonians so I am starting to have a doubt - I certainly don't want to add coma to the refractor views.

Best regards,

D25.

[Merlin66]

D25,

If you want to "try before you buy", you can borrow my x2.8 Klee and see the results for yourself... drop me a PM if interested.

Ken

[dweller25]

D25,

If you want to "try before you buy", you can borrow my x2.8 Klee and see the results for yourself... drop me a PM if interested.

Ken

Thanks - PM sent.

[KaStern_Former_Member]

Hello D25,

so if you want the barlow for planetary observation wich is done strictly on-axis

I can recommend the Klee 2.8x Barlow for your Tak.

It is very well baffled and so there will be no straylight problems.

200x with the 102/800mm needs a 4mm eyepiece (a 4mm ortho has only 3mm eyerelief)

but with the 2,8x Klee you need an eyepieve between 11mm and 12mm focal length.

Eyerelief will be about 9mm with an 12mm U.O. HD Ortho or Baader genuine Ortho,

and 10,7mm with the 12mm Edmund RKE:

Edmund Optics RKE Precision Eyepieces

In combination with the Barlow it will be about one or two milllimeters more.

Super that you can borrow the barlow from Ken

Clear skies, Karsten

[Ralf]

Sorry wrong thread.

[Kevin Ellis]

Barlows do not reduce coma. They do reduce astigmatism which is often interpreted as coma

[Merlin66]

Sorry to correct you, but the Klee was specifically designed to do that. I'll try and find the article from Telescope Making Magazine ( one of the early issues) where the whole optical design was illustrated and explained. Based on a f4 Newtonian test.

Only the Klee x2.2 and x2.8 Barlow from University Optics have this optical design.

[Kevin Ellis]

That's interesting. I would like to see that article. Have a look at this thread on Cloudy Nights

Telescope Reviews: coma correcting barlow?

[Kevin Ellis]

On the University Optics web site it say "Many claim it corrects coma in their fast Dobsonians" not the designer Heinz Klee him self.

The link to University Optics is below

Barlows and Klee Barlows from University Optics Supplies

[Merlin66]

Kevin, I must say your links have got me thinking!

Hmmm......, I'm going back to Oz to visit the family next week, so I should be able to access my library. I'll try and find the reference I'm thinking about, but I'm getting that uneasy feeling that it may have actually refered to the Pretoria eyepiece and not specifically the Klee barlow....

What ever the outcome, I'll let you know.

[Kevin Ellis]

Merlin

Back to Oz Ah......

In 2007 I spent 3 weeks in Oz to do some astronomy. The night skies were just fantastic. I also met Robert McNaught when we visited the Siding Spring Observatory.

Until I did some research prior to buying a barlow for my 13mm Ethos, I was under the impression that a barlow would reduce coma as a result of increasing the focal ratio of my telescope. But this is not the case.

I still bought a barlow. Infact my 13mm Ethos works very well with my Televue 2" x2 Big Barlow in my 8" f4.5 newtonion.

[Merlin66]

Rob used to visit us in the 80's - he was a real hippy!!

( I was President of the ASV, and astrophotographic section director for almost 10 years)

Have you had the chance to try the Ethos with the TV x2 Powermate? I think it might perform even better than the Big Barlow (I've just sold all my TV Barlows and gone over to the Powermates!!)

Anyway, I will double check the info on the Klee as promised.

[Kevin Ellis]

Merlin

So your not doing any work either.

I have not tried the powermates. I was concerned about the extra weight (4 elements instead of 2). I have also read some comments that the Big Barlow had a little more contrast than the Powermates, although I have not been able to confirm this myself. Have you noticed any difference? I do know powermates retain eye relief which would help with my Radians which already have 20mm. The barlow extends this 23mm.

Accepting the small differences in magification, my initial impression is that my barlowed 13mm Ethos has a tad more contrast than my unbarlowed 8mm radian and my barlowed 14mm radian. I need to do some more observing to be certain. The view is certainly more comfortable on the eye with the barlowed 13mm Ethos.

Robert was a really nice guy. He even showed us the raw data when he discovered his famous comet.

[Merlin66]

Well, actually I work from home, so it allows some "freedom"

I can only comment on the TV Big Barlow and the x2.5 barlow, also the AE x4 Imagemate and the KLEE's v's the Powermates.

For me, bear in mind I use them 80% for imaging, the Powermate was a standout success!! The "fixed" magnification independent ( yes I know there is SOME change) of the back focus blew me away! I honestly can't say I lost any contrast or clarity visually in the change. I use TV plossls and Naglers.

[Kevin Ellis]

Merlin

I also work from home. It is too easy to be distracted.

I suspect that visually their is little or no discernable difference in contrast between the Big Barlow and Powermates. On some nights it is too easy to be fooled by changing conditions which is why I need to do some more comparisons with my Big Barlow. My main concern was the weight of the powermate with my Ethos in my 8" f4.5 Newt.

I do not image, but prefer to draw at the telescope. One day I will post some drawings.

Must do some work

[KaStern_Former_Member]

Hello Stargazers,

in the meantime there were so many postings. Wow.

There seems to be some confusion about the coma compensating abilities of the Klee Barlows.

Please see the website of Chris Lord:

When you scroll down to the end you will see the comacompensating Pretoria eyepiece.

The lens-scheme, aberration diagrams and the point spread function of the eyepiece alone

and the eyepiece combined with an 6"f/4 Newt. Please note the off-axis coma of the

eyepiece alone, and the absence of the off-axis coma when combined with the Newt.

Same thing happens with the Klee barlows. The off-axis coma of a paraboloidal Newtonian mirror

and the off-axis coma off the Klee barlow compensate. This is waht the designer Mr. Klee

wanted to acheive. The Klee barlows were designed to be used in Newtonians, regardless

if they are slow or fast newtonains down to f/4.

I know Mr. Klee personally. What I wrote is what he told me on the phone and via email.

I own two 2.8x Kle barlows and two 2.2x Klee barlows. I conducted many star tests with

them and different eyepieces and I can tell you that the design works very well with both

my 8"f/6 Newt and 112/450mm Newt. When I focus a star in the center of the barlowed eyepice

and let the star drift towards the edge it keeps to be pinpointlike right to the edge.

I used my 25mm, 18mm, 12,5mm U.O. conical top ortoscopics, the 13mm and 11mTelevue Ploessl,

the 12mm and 8mm Edmund Optics RKE.

The 2,8x Kle is baffled very well. It is amazingly free from light scatter. Downside of the

2.8x Klee is that it moved the eyit pupil much farer out than the 2.2x Klee does.

Or the 2x and 3x Televue Barlows do. This is because the 2.8x Klee is short, but strong.

The off-axis ray bundles are bend outward and this can cause vignetting in the eyepiece

and it moves the exit pupil outward. Despite of this the 2,8x Klee works fine with my

13mm to 8mm Ortho, Ploessl and RKE. And quite good with my 18mm U.O. Ortho.

The 2.2x Klee is mor versatile. It is weaker, but longer. So it moves the exit pupil

not so far out than the 2.8x Klee does. It works fine with all of my Orthos, Ploessl and RKE.

Unfortunately both of my 2.2x Klee did lack blackening on one outer lens surface.

This leads to severe strailight when I was observing the moon.

After talking to Mr. Klee he told me wich surface was likely causing the problem and

I blackened the critical surface in one of my 2.2x Klee barlows. Now it works fine

even for lunar observation.

If you use the klee in a coma-free telescope it will add inverse of-axis coma.

Please see the first photo in this posting:

MPCC als Flattener an Megrez72? - Astronomie.de

It was made using a 72mm FD apochromat (wich does not show off-axis coma)

and a Baader MPCC coma corrector. Please not that this results in off-axis coma.

But the coma is inverse, the comet tails point to the center, not to the edge,

like it is in a Newt without a MPCC.

The Klee barlow will do the same if it is used in a coma free telescope.

But with slow refractor the Klee brlow will add only marginal off-axis coma.

In a slow Newt there is only marginal off-axis coma too.

But is a fast refractor the Klee will add severe off-axis coma.

With the 102/816mm Takahashi TSA it will add visible off-axis coma. But since you

observe planets on-axis this will not be harmful for this purpose.

The Klee is has a very good colour correction, good coatings, good polish witch results

in low glare.

But for your TSA I would recommend the 1,8x TMB Barlow or the 2x Zeiss barlow.

Both performed very well when my friend Sven Wienstein and me did a borlow and eyepiece comparison:

Barlow-Test

Maybe a translation helps.

Regards, Karsten

[Kevin Ellis]

Karsten

Thank you for the explanation.

So the Klee barlow is designed to add inverse of axis coma.

I accept what you say but I am some what puzzled. Given the virtues of a barlow that could reduce coma, why is this not claimed by University optics who sell Klee Barlows? They Say "Many claim it corrects coma in their fast Dodsonians" not themselves or Heinz Klee.