Klee 2.8 Barlow

[KaStern_Former_Member]

Hello Kevin,

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.

I really do not know. I only can tell you about my observations and what Heinz Klee

did tell me about his barlow design. I cannot tell why the University Optics does not

advertise the capabilities of the Klee barlow in a more direct way.

Cheers, Karsten

[Kevin Ellis]

Or could it be that UO are not convinced about the claims.

[KaStern_Former_Member]

Or could it be that UO are not convinced about the claims.

I porpose you should phone UO and ask Mr Seyfried.

But keep in mind that he is the vendor, not the optical designer.

[Kevin Ellis]

Vendor yes, but the 2.2x Klee Barlow was specifically designed for University Optics by Heinz Klee.

On the UO web site there is a review of the 2.2x Klee Barlow done by a friend of Heinz for UO. You would therefore think that UO are fully aware of the optical qualities of the 2.2x Klee Barlow, No mention of any coma correcting.

Was that friend you KaStern?

I am not saying that the Klee is not a good barlow. Does it correct coma ? Well that's the question.

I have now found three main threads on Cloudy Nights discussing that very point. They make an interesting read.

Telescope Reviews: coma correcting barlow?

Telescope Reviews: Re: UO 2.8 and 2.2 Klee barlows

Telescope Reviews: UO 2.8 and 2.2 Klee barlows

Note the phrase "reduce the perceived coma" used in one of the postings.

And the review on UO

Barlows and Klee Barlows from University Optics Supplies

[KaStern_Former_Member]

Vendor yes, but the 2.2x Klee Barlow was specifically designed for University Optics by Heinz Klee.

On the UO web site there is a review of the 2.2x Klee Barlow done by a friend of Heinz for UO. You would therefore think that UO are fully aware of the optical qualities of the 2.2x Klee Barlow, No mention of any coma correcting.

Was that friend you KaStern?

I am not saying that the Klee is not a good barlow. Does it correct coma ? Well that's the question.

I have now found three main threads on Cloudy Nights discussing that very point. They make an interesting read.

Telescope Reviews: coma correcting barlow?

Telescope Reviews: Re: UO 2.8 and 2.2 Klee barlows

Telescope Reviews: UO 2.8 and 2.2 Klee barlows

Note the phrase "reduce the perceived coma" used in one of the postings.

And the review on UO

Barlows and Klee Barlows from University Optics Supplies

Hi Kevin,

thank you for compiling these threads. It is an amazing thing.

I heard about the Klee Barlow and soon was aware that a coma-compensating barlow

would be very nice for use my Newtonian. Since the Klee was only avalable in the USA

I asked if there is another coma-compensating barlow on the market.

But instead of getting the information if there is another comacompensating barlow or not

the ability of the Klee Barlow was questioned by some users. Most of them

did not even own the Klee or had observed with the Klee.

None of them had seen a spot dagram of the Klee with an 6f/4 parabolical mirror.

This shows precisely why forums are not allways suited to get valid information.

I was banned from CN (I insited on asking where the country of origin of the TMB 130 SS was) ,

was re-installed after 14 month (my pal Taj made a contact to one CN Mod

sincemy own emails to the CN forum-moderation did not get answered)

and after another thread concerning the TMB 130 SS in am banned again

(again without any information how long).

I personnally think that that forum sometimes acts in a way that leads to information-suppression.

You may find that thread an Yahoo Groups interesting:

Yahoo! Groups

That`s the way it is. My lesson in some years of memebership in different forums

(german forums, later american and british forums) was this:

If I want to get valid information I need to get first-hand information.

So I try to read books on the subject.

Or I address to the optical designer if I need pricise information on a special optical device.

Or I ask an optical designer for general information on barlow.

Or I try to observe myself with the optical device.

Harrie Rutten was so kind to do a fast design of a cemented 2-lens coma-compensating barlow

and emailed the spots and design data to me.

It was Harrie Rutten (Harrie Rutten and Martin van Venrooij wrote the book "Telescope Optics")

who confirmed that the Klee is specially made to compensate coma of paraboloidal Newts:

Welche Barlowlinsen taugen was ??? - Astronomie.de

You asked:

On the UO web site there is a review of the 2.2x Klee Barlow done by a friend of Heinz for UO. You would therefore think that UO are fully aware of the optical qualities of the 2.2x Klee Barlow, No mention of any coma correcting.

Was that friend you KaStern?

No, that was a long time friend of Heinz Klee who lives in South Africa.

Mr Klee did mention that report when I talked to him on the phone,

and he said that it is only a part of what his friend L.B. reported to him

and Mr Klee did send to Mr Seyfried.

I am not saying that the Klee is not a good barlow. Does it correct coma ? Well that's the question.

No question for me. It does.

Unfortunately I cannot provide any spot diagrams. Heinz Klee would be able to do,

but he does not own the rights on the design, Mr Seyfried does own it.

I can tell you what I have observed, but since you do not know me I understand that you doubt my words.

I fear that this will be a never-ending story, like on CN.

Sorry for some grief in my post,

Karsten

[Kevin Ellis]

You have been BANNED Karstern.

Fantastic.

You know you can always talk to me.

It’s not a question of disputing your findings, although others have. It’s that "coma correcting" has not been claimed by the vendor University Optics, who you have advised owns the optical design of the 2.2x Klee Barlow.

By not doing so, they have left the whole issue up for debate.

I did email UO but their reply was ambiguous. I have therefore asked them for clarification.

Thank you for the interesting Yahoo link.

The other link, which I assume concerns the Klee Barlow, is in German, so needs translating.

My German is non existent.

Just remember, this is just a discussion about astronomy. Something we all love doing.

Banned Karstern

Respect

[KaStern_Former_Member]

Hello Kevin,

The other link, which I assume concerns the Klee Barlow, is in German, so needs translating.

oh, sorry, I forgot to do it. Mr Rutten wrote:

Die Klee Barlow: vorsicht bei Nicht-Newtons denn die Barlow ist speziell entworfen um die Koma zu eliminieren. Wird also bei einem aplanaten Koma introduzieren.

This translates to: "The Klee Barlow: Caution with non-newtonian telescopes,

this barlow ist specially designed to eliminate the coma. It will introduce koma

in an aplanatic telescope."

Just remember, this is just a discussion about astronomy. Something we all love doing.

Yes. But in the case of the Klee Barlow it is too a discussion about Optics.

From the optical point of view things are really clear.

And, with the Klee Barlow it is too a discussion about economics.

If you point out that is a real coma-compensating-newtonian barlow

you won`t sell many of them to people with aplanatic telescope designs.

And it is a discusion about information supprression. If you carefully read the threads

wich you have linked you will discover how much the real information is pushed aside

by some users.

And concerning the CN ban (see how the CN Moderators reacted when a link to

Rodger W. Gordon`s article on the use of the smyth-group

A Chronological History of Smyth & Barlow Lenses

hostet on chris Lord`s website was linked at CN:

Yahoo! Groups

it is a discussion on how free the speach in a forum is, or not is.

Concerning astronomy and the Klee Barlow I can tell you that I did observe yesterday.

I was out to check an eyepiece that I recently bought.

I checked the eyepiece by observing some stars, let them pass through the field of view,

observed Vega and discovered what I feared after I inspected the eyepiece during daylight:

The eyepiece suffer from straylight due to bad baffling

I will have to send it back.

I had my 10,5mm Pentax XL and my 7mm Pentax XW with me to compare.

And I took my 2,8x Klee Barlow with the 18mm U.O. Ortho as well as my modified

2,2x Klee Barlow mit my 12,5mm U.O. Ortho to check again.

I was observing Alioth (Epsilon Ursae Majoris)

Epsilon Ursae Majoris - Wikipedia, the free encyclopedia

wich was riding relatively high in the sky. I fokussed Aloith in the center of the eyepiece

and lt him drift towards the edge of the field of view. Doing this I observed how the star looked on his way. First I took the 2.8x Klee and the 18mm Ortho.

In the center Alioth was round, bright, with 4 spikes (I have a 4-vane spider in my 8"f/6 ATM Newt).

The star did show the airy disc and about 3 rings surrounding it, due to the instable air.

In rare moments there was only one ring visible. During the passage the star kept beeing round.

In the very near of the edge it became slightly bigger and I noticed that the star was

slightly defocussed.

I observed Alioth with my 8"f/6 Newt, my modified 2,2x Klee Barlow and a 12,5mm U.O. Ortho.

I focussed the star in the center and then let him drift towards the edge.

The star was round sharp and free of lateral coulour even when he hit the edge.

This was very impressive to me.

I remembered what Heinz Klee did tell me concerning both Klee barlows:

"I can design a barlow wich compemsates the off-axis coma of the parabolic mirror.

But since I do not know what the eyepiece designer did I will not be able to compensate

the eyepiece aberrations. If the eyepiece is designed in a way would habe designed it

things will be o.k.

If not, there will be aberration discernable in the system Newt/Klee Barlow/eyepiece."

Maybe this is one reason why Mr Seyfried does not advertise the coma-compensating ailities

of the Klee Barlows.

One of my 2,2x Klee is "modified". There was one outer lens sirface wich is not blackened

allthough it should be. When I pointed the barlow to a window it clearly indicated the problem.

I observed the moon, and allthough the 2.2x barlow did a great job and showed

a lot of fine detail it was obvious that the contrast wa lowered by severe straylight.

I compared with my 2.8x Klee wich has superb baffling and the 3x Televue wich is o.k.

So I talked to Heinz Klee and reported my findings. He told me that this is the same

wich his friend L.B. reported to him after receiving the pre-production sample of the

2.2x Klee.

L.B. wrote a report to Heinz Klee in wich he pointed out the advantages and disadvantages

of the pre-production 2.2x Klee Barlow. Heinz Klee did send the report to U.O.

You find the advantages partly on the U.O. website. Unfortunately U.O.

seems to have decided to not change anything with the internal blackening.

So I cannot recommend it for Lunar observation. If you do the blackening it is perfectly

suited for all type of observation wit a good Newt. CCompared to the 2.8x lee the 2.2x

does not move the exit pupil so far out. So you can use it even with the 25mm Ortho

wich is quite imposible with the 2,8x Klee.

Banned Karstern

Respect

I do not understand this?!

Cheers, Karsten

[Kevin Ellis]

Hello KarStern

I remembered what Heinz Klee did tell me concerning both Klee barlows:

"I can design a barlow wich compemsates the off-axis coma of the parabolic mirror.

But since I do not know what the eyepiece designer did I will not be able to compensate

the eyepiece aberrations. If the eyepiece is designed in a way would habe designed it

things will be o.k.

If not, there will be aberration discernable in the system Newt/Klee Barlow/eyepiece."

Maybe this is one reason why Mr Seyfried does not advertise the coma-compensating ailities

of the Klee Barlows.

You may be correct but either way UO have not confirmed coma correcting on their web site or in their email to me.

Concerns about other aberrations may be the reason other manufacturers are not making coma correcting barlows.

And concerning the CN ban (see how the CN Moderators reacted when a link to

Rodger W. Gordon`s article on the use of the smyth-group

I guess if you indirectly imply that an eyepiece manufacturer has breached a patented design you will be banned.

I observed Alioth with my 8"f/6 Newt, my modified 2,2x Klee Barlow and a 12,5mm U.O. Ortho.

I focussed the star in the center and then let him drift towards the edge.

The star was round sharp and free of lateral coulour even when he hit the edge.

This was very impressive to me.

That is very good but is your 8" f6 Newt a real test? Your 4.5" f4 would be a better test. I have never felt the need for any correction when using quality eyepieces in my 6" f6 Newt. Even in my 8" f4.5 Newt I only feel the need to use a paracorr with eyepieces longer than 10mm.

You find the advantages partly on the U.O. website. Unfortunately U.O.

seems to have decided to not change anything with the internal blackening.

So I cannot recommend it for Lunar observation. If you do the blackening it is perfectly

suited for all type of observation wit a good Newt.

Yes I did notice that UO gave a more favourable review when looking at the moon

Did I read correctly on another thread that CN were suppressing your views on the Klee Barlow or is this just as a result of a general ban?

Quote:

Banned Karstern

Respect

I do not understand this?!

English humour. Take it as a complement.

Cheers Kevin

[KaStern_Former_Member]

Hello Kevin,

You may be correct but either way UO have not confirmed coma correcting on their web site or in their email to me.

Concerns about other aberrations may be the reason other manufacturers are not making coma correcting barlows.

What type of aberration do you talk about? In a parabolidal newtonian mirror only one aberration is corrected:

Spherical aberration, for the axial point. There are several aberrations left:

1) off-axis coma. It is the most destructive aberration of a fast Newt.

2) off-axis astigmatism.

In a Newtonian, the edge of the mirror defines the location of the aperture stop.

With such an arrangement we find that the sagittal image surface is flat, and that

the tangential image surface is curved, meaning that the mirror introduces astigmatism.

The tangential surface is spherical (first order approximation), with the sphere having

a diameter equal to the focal length of the primary mirror. The radius of this sphere

is located half way between the mirror surface and the mirror focus.

3) field curvature. As you can see from the above field curvature is mild.

So what aberrations should a barlow for Newts correct?

It is quite easy to answer:

It should correct the most bothersome aberration: Coma.

In a typical 2-lens refractor there will be the following aberrations:

1) no coma

2) astigmatism

3) longitudinal colour aberration

4) lateral colour

5) field curvature

All of these differ much with different glass, different focal length, different aperture.

So you cannot create a barlow wich compensates for all type of aberration.

It is "easy" to create a barlow that compenates the newtonian mirror aberrations.

Imagine a 300mm f/4 mirror, a 250mm f/4,8 and a 200mm f/6 mirror.

If the barlow compensates the coma of the 300mm f/4 mirror, it will too compensate

the coma of both other mirrors too, since they are only a part of the bigger mirror.

That is very good but is your 8" f6 Newt a real test? Your 4.5" f4 would be a better test.

The 4.5" f/4 would have been a harder test. But I was out with my 8"f/6 because

I wanted to check a recently bougth eypiece for this scope. Additionally I did the

check with both Klee barlows.

Some month ago I have done a check with the small f/4 Newt. I performed the same star drift test. Both Klee barlows compensated for the off-axis astigmatism of the f/4 mirror.

I have never felt the need for any correction when using quality eyepieces in my 6" f6 Newt.

The difference between quality eyepieces and shabby low-cost eyepieces in fast telescopes

is that the latter react with severe astigmatism when they are confronted with the

steep off-axis light bundles of fast teleskopes. No matter what type of scope.

These eyepieces show severe off-axis astigmatism. Quality eyepieces often are

better corrected and do not react with off-axis astigmatism.

If you add a barlow to the cheap eyepiece it will not show off-axis astigmatism.

Some people therefore think that this barlow corrects for off-axis coma.

Many people cannot distiguish between coma and astigmatism.

Even in my 8" f4.5 Newt I only feel the need to use a paracorr with eyepieces longer than 10mm.

Chris Lord`s Website provides an interesting article about off-axis aberration in Nets:

http://www.brayebrookobservatory.org/BrayObsWebSite/HOMEPAGE/forum/AA_error_article.pdf

The diameter of the diffraction limited field of view of a 8"f/4,5 Mirror is about 160 arcseconds.

A 10mm Plössl will have a field stop diameter of about 8,3mm diameter. With your 8"f/4.5 Newt it will give you a 0.528° field of view. This is 1900 arcsecondes diameter.

So there will be plenty of off-axis coma.

But since a normal Ploessl will show severe off-axis astigmatism this will mask

the coma of the mirror.

If you add anormal quality 2x barlow and use a 20mm Ploessl the true field of view

will be the same as with the 10mm Ploessl without a barlow.

With the barlow ahead the 20mm ploessl will not show off-axis astigmatism .

Then you will discover the off-axis coma of the mirror if you push a star towards the edge.

If you add a 2.2x Klee Barlow to 22mm Ploessl the ploesl will not show astigmatism.

In addition the off-axis coma of the Newt`s mirror is cancelled.

If you push the star towards the edge it will stay round until it hits the field stop.

But if you add tha Klee barlow to a coma-free teleskope it will add coma of the opposite sign

of a parabolic mirror with the same f/ratio. So it does not make sense to take a Klee barlow

for a fast refractor.

Did I read correctly on another thread that CN were suppressing your views on the Klee Barlow or is this just as a result of a general ban?

No. I was banned for my posts concerning the TMB 130 SS.

I wanted to read in public forum where it is made, since I found differing statements

in different forums. T.M.Back stated in his yahoo forum that the lenses were made in Japan.

M.Ludes stated that the lenses were made in Taiwan. There was some trouble between both

and on CN i could not find a clear staement what the country of origin is, so I asked

and I soon found myself in a wasp nest.

I was banned (the original thread is much shortened now, many posts have been deleted).

After 14 month I was set free again. A friend of mine made contact to a CN mod,

since my own emails kept unanswered by CN.

After some month I was astonished to find a weird thread and opposed to what they wrote

and I was banned again (again without telling me how long). Again some posts were deleted.

I am under the impression that it does not make much sense to post here.

From what I have seen I think that information gets suppressed if it is against

the interest of the main vendor or other "supporting" vendors.

I prefer a forum where a clear question (where are the lenses of the TMB 130 SS made?)

gets a clear answer (Taiwan, astronomics finally answered this question to another user

after I was banned again).

English humour. Take it as a complement.

THX. Cheers, Karsten

[KaStern_Former_Member]

Amateur Telescope Optics

The above website gives a very good overview on the different telescope aberrations.

[Kevin Ellis]

Hello Karsten

I see that you are online as I type.

As usual you provide plenty of useful information.

Is your 4.5" f4 Newt an Orion Starblast. If so, are you pleased with it.

New Question which I know should be a new thread but continues the theme on fast scopes.

My 8" f4.5 Newt has a 63mm secondary mirror 31.5% obstruction. This is Ok, as I have a fully illuminated field and find that the 13mm Ethos with a TV Paracorr works very well. But I have always been suprised by the high level of contrast dispite the 31.5% obstruction. I have not detected any loss in contrast when compared to a fellow club members 8" f6 Newt scope which has a 25% obstruction or other 8" Newts with smaller obstructions. As a result, I have not considered changing the secondary mirror. The following link, which you posted on another older thread, would indicate that I should see a difference. Is this also your experience

Thierry Legault - What are the effects of obstruction ?

Cheers Kevin

[KaStern_Former_Member]

Hello Kevin,

yes, my 4,5"f/4 is a skywatcher with parabolic mirror.

It is o.k. but I have to change some things:

I have a HP tube and a 2" helical fokusser for it.

Then it will be very nice for wide field viewing.

Thierry Legault - What are the effects of obstruction ?

I like Thierry Legault`s website. He provides very good information and superb astrophoto.

Your 8"f/4,5 has a bigger central obstruction than a typical 8"f/6 Dob wich has 25%

or my 8"f/6 ATM Dob wich has 20% .

Could you see the difference when viewing a planet or the moon?

One thing is for shure:

It will need

1) perfect collimation

2) nearly perfect seeing conditions

3) perfectly focussed

4) equally good eyepieces in both scopes

5) side-by-side comparison

6) equally good optics in both scopes

I remeber a comparison between my 8"f/6 ATM DOb with 20% central obstruction

and a VMC with about 40% central obstruction. Both scopes were collimated

(confirmed by the star-test), seeing was very good.

We observed the Moon with 250x to 280x. On the border between light and shadow

there were some beatyful craters. I remeber that the structures at a crater wall were

more hard in my dob, wheras they appeared more "rounded" in the VMC.

Some low contrast rimae were contrastier in the Newt.

O.K. 40% obstruction is a lot. I think 31% is not so bad. I have obseerved with an

8"f/4,5 Orion U.K. Newt and it gave very pleasing views.

A little bit more obstruction is the price wich one has to pay for the wider field views.

Greets, Karsten