129 replies to this topic

[Mordakyblu]

Last night I look a look at the Moon and Venus. The air here in LA was pretty turbulent. At 100x I could see the air boil at the edge of the
Moon’s image. Despite the air my Orthos and Kellners edged out my TV
plossels. When observing I enjoy swapping out eyepieces and adding
filters. I like to try and find the optimum combination for the image and the conditions.

[Jim45157]

yes orthos are way better learned that years ago  i dont know about the wide field eyepieces but orthos are great

[j.gardavsky]

Last night I look a look at the Moon and Venus. The air here in LA was pretty turbulent. At 100x I could see the air boil at the edge of the
Moon’s image. Despite the air my Orthos and Kellners edged out my TV
plossels. When observing I enjoy swapping out eyepieces and adding
filters. I like to try and find the optimum combination for the image and the conditions.

In principle yes,

but it depends which Abbe orthos and Kellners you will be comparing with the TV Plössls.

 

JG

[BillP]

Last night I look a look at the Moon and Venus. The air here in LA was pretty turbulent. At 100x I could see the air boil at the edge of the
Moon’s image. Despite the air my Orthos and Kellners edged out my TV
plossels. When observing I enjoy swapping out eyepieces and adding
filters. I like to try and find the optimum combination for the image and the conditions.

I don't use Kellners any more, but heartily agree that Abbe Orthos rock!     A wonderful design that continues to put up quite outstanding results even from non-premium versions.  The TV Plossls are also a well build eyepeice, but for my tastes their level of rectilinear distortion, shorter than Plossl-normal eye relief due to the patented concave eye and field lens surfaces, smaller than typical 50 degree AFOV for a Plossl, and inability to take conventional Barlow with vignetting, make them a tough sell for me - and I've had the complete set multiple times in my observing lifetime!!  For an eyepiece with a 50 degree or smaller AFOV, will take a good Abbe Ortho over any other (e.g., while things like AP-SPLs and TMB Supermonos have come and gone in my stall, the Abbe remains)!

Edited by BillP, 08 May 2020 - 12:56 PM.

[Allan Wade]

I'm with Bill. I have a TeleVue Plossl double set for a bit of fun. They are good eyepieces. But the main telescope case is full of Abbe Orthos. Lots of types and brands have come and gone, but the ZAO's and Tak Abbes remain. They're just so excellent in all my scopes, even at f/3.3, whether its planets and moons, or magnitude 18 galaxies.

[Thomas_M44]

I'm looking forward to comparing my KK Fujiyama Abbe ortho's against a recently acquired set of current-production Edmund  RKE EP's

 

I bought the RKE 28mm, 21mm, 12mm and 8mm. Strangely, Edmund is not currently offering the 15mm RKE in mounted form, rather only available as an unmounted lens set.

 

I suspect the RKE's really would do better in f/8 or slower focal-length scopes, but I'm hopeful that they might be worthwhile in my f/7 TV-85.

 

I also am also hopeful the 2.4X 2" Dakin Barlow will work well with both the RKE's and the KK Abbe ortho's.

 

So much fun  : )

Edited by Thomas_M44, 09 May 2020 - 02:41 AM.

[lylver]

Hello RKE is end of life for Edmund, the formula is no more secret now, I got it crypted from Edmund 3 years ago and trace it with Zemax and pass it to starman1 during informations exchange.

It is a well balanced eyepiece that you can use for planetary at long f/D (start @ f/12 for the 8mm, a bit longer for the 12mm which is homothetic in design )

At f/7 it is a bit too low but still enjoying. I had a vintage one that was impressing with a Baader VIP barlow on a 80ED f6 refractor but no match against a TV Radian except, surprisinlgy for chromatism. (Venus is rich with violet color so ...)

It matches better telescope with a little chromatic dispersion : maksutov matches well as semi-apo or long f/D refractor.

As the build quality is less than before (contractor, no more Edmund), I would search a vintage one for the 8 ou 12mm. At longer focal length, there should be no difference.

Excellent design for f/12 planetary use, 12.5° field high polystrehl(>0.95) is my criteria

As I am working on the Clave formula, I can say principe governing their design is similar, but the manufacturing of the RKE is much simpler, quality is easier to attain.

Using it properly you should, as Edmund write in the specs for the RKE, make the focus around 70% field (15° off axis), not in the center.

Clavé 10mm is much better for polystrehl, has also better focus to be done out of the center at the max of the lateral planetary important color. (546-616nm) about 1/3 of the AFOV (8°-15°). The astigmatism and lateral color is tuned near to the the center. Albert König made this formula for the Zeiss B apo objective he designed, so the need of best color correction. SAF tuned it differently, reducing field for sharpness at lower f/D, enhancing the eye relief, tuning astigmatism and color correction.

Left part of the sketch is for 25° field (in fact same level of astig. compared to RKE if you match their field), right has been limited to 20° to show spot (planetary over 21.5° off axis is useless due to eye fatigue to roll farther and inherent eye astigmatism when rolling off axis)

Kellners are top eyepiece too but you should keep them for chromatic refractor best for f/10 with refractor that are between Sidgwick and Conrady chromatism criteria.

Kellners are flat EP, low distorsion and minimal aberration of the exit pupil. If you find old russian lanthanum Kellner multicoated for top transmission you can even go to f/D 8 even 7 for comet catcher refractor and have 56° on them !

They are also "CVD" eyepiece that compensate the lateral color of the refractor specified upper.

I got a 25mm old Lumicon branded one, multicoated (no internal reflexion), stunning EP on a f/12.5 80mm refractor.

Edited by lylver, 09 May 2020 - 05:18 AM.

[Thomas_M44]

Hello RKE is end of life for Edmund, the formula is no more secret now, I got it crypted from Edmund 3 years ago and trace it with Zemax and pass it to starman1 during informations exchange.

It is a well balanced eyepiece that you can use for planetary at long f/D (start @ f/12 for the 8mm, a bit longer for the 12mm which is homothetic in design )

At f/7 it is a bit too low but still enjoying. I had a vintage one that was impressing with a Baader VIP barlow on a 80ED f6 refractor but no match against a TV Radian except, surprisinlgy for chromatism. (Venus is rich with violet color so ...)

It matches better telescope with a little chromatic dispersion : maksutov matches well as semi-apo or long f/D refractor.

As the build quality is less than before (contractor, no more Edmund), I would search a vintage one for the 8 ou 12mm. At longer focal length, there should be no difference.

Excellent design for f/12 planetary use, 12.5° field high polystrehl(>0.95) is my criteria

8mm-color-field-0,64mm-pupil-fD12.jpgRKE8.jpg

As I am working on the Clave formula, I can say principe governing their design is similar, but the manufacturing of the RKE is much simpler, quality is easier to attain.

Using it properly you should, as Edmund write in the specs for the RKE, make the focus around 70% field (15° off axis), not in the center.

Sir, I find your above posted RKE and Kellner information simply fascinating.

 

As you have illustrated, the RKE's will become an asset when I some day finally build or obtain an f/15 refractor.

 

Thanks sincerely for sharing

Edited by Thomas_M44, 09 May 2020 - 04:37 AM.

[TG]

I have 2 pairs of microscope eyepieces, all Nikon, that I've adapted for my binoviewer. One pair is 24mm which has fine focusing adjustment (useful for binoviewer) and is marked "plan" meaning flat field. The second pair is 12.5mm and has very nice eye cups attached. Both have 50* fields and are among the sharpest and lowest scatter ones I have used. Inspecting them I believe they are just 3 element designs so how Nikon did this is a mystery to me.

[BillP]

I'm looking forward to comparing my KK Fujiyama Abbe ortho's against a recently acquired set of current-production Edmund  RKE EP's

 

I bought the RKE 28mm, 21mm, 12mm and 8mm. Strangely, Edmund is not currently offering the 15mm RKE in mounted form, rather only available as an unmounted lens set.

 

I suspect the RKE's really would do better in f/8 or slower focal-length scopes, but I'm hopeful that they might be worthwhile in my f/7 TV-85.

 

I also am also hopeful the 2.4X 2" Dakin Barlow will work well with both the RKE's and the KK Abbe ortho's.

 

So much fun  : )

I used to use them in my 10" f/4.7 Dob all the time!  On planetary the 8mm gave up absolutely nothing to the TV 7.4mm Smoothie Plossl at the time and the newer 8mm when they released that.

Edited by BillP, 09 May 2020 - 07:12 PM.

[Moondust]

Speaking of orthos, I'm thinking of picking up the 4mm Tak Abbe Ortho while it's still available to add my KK 4mm ortho and Tak 4mm TOE. I don't tend to spend much money on low to mid power eyepieces because most of my observing interest lies in lunar and  planetary. Is the 4mm Tak Abbe a stellar eyepiece worth getting or is it the stinker in the line up? I know it is the only one without a rubber eyeguard. I did some research and there is not a lot out there on this eyepiece and what is out there some of it is rather negative. Just wondered if anyone here used one and their opinion.   

[Allan Wade]

Speaking of orthos, I'm thinking of picking up the 4mm Tak Abbe Ortho while it's still available to add my KK 4mm ortho and Tak 4mm TOE. I don't tend to spend much money on low to mid power eyepieces because most of my observing interest lies in lunar and  planetary. Is the 4mm Tak Abbe a stellar eyepiece worth getting or is it the stinker in the line up? I know it is the only one without a rubber eyeguard. I did some research and there is not a lot out there on this eyepiece and what is out there some of it is rather negative. Just wondered if anyone here used one and their opinion.   

The 4mm Tak Abbe is a bit of a dud unfortunately. Sad because of how stellar the rest of the Tak Abbe set is. The 6 and 4 are the only two focal lengths I could compare directly to the ZAO II’s. I never separated the Tak and ZAO 6mm on deep sky targets in the 32”. 
 

With the 4mm Tak Abbe, anytime a bright target was outside the field of view and also crossing the field stop, all sorts of reflections could be seen bouncing around inside the eyepiece barrel. The 4mm is a very different design to the rest of the set, with a long barrel inside the main barrel. With the ZAO 4mm the object would snap into view as it crossed the field stop. With the Tak 4mm you could tell it was coming from a long way out, and when it was in the field of view, you could see all the internal parts of the eyepiece because of the reflected light everywhere.

 

The TOE 4mm is a better eyepiece. I can usually make decisions pretty quick in the 32” and I sell off the redundant eyepiece. But I’ve been comparing the 4mm ZAO II and TOE for over a year and still don’t know which way to swing.

[lylver]

 I never separated the Tak and ZAO 6mm on deep sky targets in the 32”. 
 

Not surprising, you were using eyepieces made for f/8.

 

We tested and try last summer some range of EP on a motorised dobson : 29" f/3.3 (around maybe faster) also Lockwood mirror.

We were looking at the cat's eye nebula (NGC 6543)

 

Best was an astroplanokular modernised based "SPLER" 4.9mm eyepiece from Stellarvue behind a paracorr°. (eyepiece is similar in concept to a Vixen LV/NLV)

Il think because the internal barlow elevated the internal f/D up to f/14 at which the "18mm fl eye part" of the SPLER worked clean.

Vic was surprised when I did feedback for a late use of this EP. Please note that he asked for modification on this EP (coating/spacing), but didn't designed it completely.

 

It is very hard to have high resolution in a very open telescope, doing comparisons in bad optical conditions is quite futile and can give random results.

 

About ZAO eyepieces : think about "faster objectives" in 1994.

About "Tak" ortho, think about the faster from Takahashi.

° : paracorr helped

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[BillP]

Not all Abbes are alike.  The ZAO-Is were designed to work well as low as f/7.  The ZAO-IIs were designed to work well at f/4.  I imagine things like the older CZJs were probably made for f/8-10.  Unfortunately in the process to make them work better at shorter focal ratios, the FOV loses some of its name sake of being orthoscopic and off-axis rectilinear distortion is introduced.  Not a lot, but immediately visible once you move off center-line with the ZAO-IIs, whereas older generations like the vintage Celestron volcano Orthos only start to show the slightest once you are about 50% out from center.  I would imagine internal baffling considerations might differ as well with the fastest focal ratios given the steeper light cone.

 

I've also noted over the years that the smallest 4mm Abbes have a lot of hits and misses with some being quite good and others duds, even in the same brand.  So I consider it more of a luck of the draw with any 4mm Abbe as to whether it will be good or not.  This includes the ZAOs as have borrowed some real duds of those in the 4mm focal length.  All other focal lengths have always been outstanding.

Edited by BillP, 10 May 2020 - 11:13 AM.

[vahe]

 The ZAO-Is were designed to work well as low as f/7.  The ZAO-IIs were designed to work well at f/4.  

 

A while back I asked Roland if ZAO-I and ZAO-II were different, here is his reply;

.

"They are optically the same, mechanically a bit different. The newer ones have smaller field stops because a few picky people complained in the past that the outer part of the field was not sharp in the version 1, so Baader had them made with smaller field stops."

.

Vahe

[BillP]

A while back I asked Roland if ZAO-I and ZAO-II were different, here is his reply;

.

"They are optically the same, mechanically a bit different. The newer ones have smaller field stops because a few picky people complained in the past that the outer part of the field was not sharp in the version 1, so Baader had them made with smaller field stops."

.

Vahe

Yup...Baader says vs. RC says vs. whatever-other-vendor says.  Can't say who is correct on the face of it, but when one vendor contradicts another vendor about specs, I tend to not go with the competing vendor simply because of their conflict of interest when talking about a competitor.  But you know, easy enough to get a 10mm or 16mm ZAO in version I and II and compare for off-axis RD and star test off-axis in say an f/5 scope to see if any difference.  Don't know if anyone has done that.

Edited by BillP, 10 May 2020 - 04:47 PM.

[Moondust]

The 4mm Tak Abbe is a bit of a dud unfortunately. Sad because of how stellar the rest of the Tak Abbe set is. 

Why didn't you swap it out for another sample, did you ever get a chance to view through another one? My 4mm Kokusai Kohki ortho actually kicks my 4mm Tak TOE's butt when it comes to on axis resolution plus it is noticably brighter, but the TOE is so darn consistent across the entire field where the KK is not, that I am keeping it. I know the 4mm Tak Abbe ortho has a 90 day return policy. I may just order one hoping that I get lucky.

Edited by Moondust, 10 May 2020 - 07:13 PM.

[lylver]

Not all Abbes are alike.  The ZAO-Is were designed to work well as low as f/7.  The ZAO-IIs were designed to work well at f/4.  I imagine things like the older CZJs were probably made for f/8-10.  Unfortunately in the process to make them work better at shorter focal ratios, the FOV loses some of its name sake of being orthoscopic and off-axis rectilinear distortion is introduced.  Not a lot, but immediately visible once you move off center-line with the ZAO-IIs, whereas older generations like the vintage Celestron volcano Orthos only start to show the slightest once you are about 50% out from center.  I would imagine internal baffling considerations might differ as well with the fastest focal ratios given the steeper light cone.

Yes you are right, but I would said the old classic Abbe SF5+SK7+SF14+BAF5 before 1950, was more for f/12. (came from microscopy which is f10-f16)

Le "colo-eye" aka Nikon Mittenzwey-Abbe design in BK7-F3 was better and match for f/10 but with very high field curvature. (Aki Saïto from VIxen included the 4mm ortho M-A in his eyepiece ortho serie, other were symetrical or were Or. Pl)

The ortho-HD is for f/8.5 according to my polystrehl criteria of .95 strehl @12.5° off-axis angle. (Thanks to Vla for the design specs)

 

About baffling of the ZAO : yes you have tested it, me no. But I can easily imagine that heavy glass included can make it work at f/4 with reduction of the high strehl field, but still near 100% strehl in center. The condition is to control the spherical aberration : high index is enough to do this in the very center. (coma, astigmatism and chromatism are very small with small off axis field)
More classic glass like for the Clave (no lanthanum : SK5,F2,SF10) make it workable @f/5 with small high strehl field. (initially made for f/14 behind a barlow, but very linear)

[SandyHouTex]

Yup...Baader says vs. RC vs. whatever-other-vendor says.  Can't say who is correct on the face of it, but when one vendor contradicts another vendor about specs, I tend to not go with the competing vendor simply because of their conflict of interest when talking about a competitor.  But you know, easy enough to get a 10 or 16 in version I and II and compare for off-axis RD and star test off-axis in say an f/5 scope to see if any difference.  Don't know if anyone has done that.

Since Baader was heavily involved with Zeiss while these were being made, I would believe Baader.  Not to mention I’m pretty sure that Baader did the mechanical design.  Zeiss, I think, did the lenses, but even that is not a certainty.  Right now, and for quite a while before now, in the photography world, there are many Zeiss lenses supposedly being made for Sony cameras.  In fact they are made by Sony, and Sony pays a fee, to put the Zeiss name on them.  I wouldn’t be surprised if the ZAO I and ZAO II lenses were made somewhere else.  It’s not like Zeiss is the only company that can leave a lens on the polishing machine longer to “get the grey out”, as the term that is frequently used to polish out the sub-surface cracks.

Edited by SandyHouTex, 10 May 2020 - 03:02 PM.

[SandyHouTex]

Why didn't you swap it out for another sample, did you ever get a chance to view through another one? My 4mm Kokusai Kohki ortho actually kicks my 4mm Tak TOE's butt when it comes to on axis resolution plus it is noticably brighter, but the TOE is so darn consistent across the entire field where the KK is not that I am keeping it. I know the 4mm Tak Abbe ortho has a 90 day return policy. I may just order one hoping that I get lucky.

I read somewhere awhile back, maybe on Barry Gooley’s website Kohkasi Kohi (yea, I probably spelled that wrong) that not very many manufacturers in Japan ever made 4mm Orthos because the lenses were so hard to make, hard to orient properly, and hold squarely in the eyepiece.  Maybe that is the problem.

[SandyHouTex]

Not all Abbes are alike.  The ZAO-Is were designed to work well as low as f/7.  The ZAO-IIs were designed to work well at f/4.  I imagine things like the older CZJs were probably made for f/8-10.  Unfortunately in the process to make them work better at shorter focal ratios, the FOV loses some of its name sake of being orthoscopic and off-axis rectilinear distortion is introduced.  Not a lot, but immediately visible once you move off center-line with the ZAO-IIs, whereas older generations like the vintage Celestron volcano Orthos only start to show the slightest once you are about 50% out from center.  I would imagine internal baffling considerations might differ as well with the fastest focal ratios given the steeper light cone.

 

I've also noted over the years that the smallest 4mm Abbes have a lot of hits and misses with some being quite good and others duds, even in the same brand.  So I consider it more of a luck of the draw with any 4mm Abbe as to whether it will be good or not.  This includes the ZAOs as have borrowed some real duds of those in the 4mm focal length.  All other focal lengths have always been outstanding.

I just wanted to thank you for the analysis of the ZAO Is and ZAO IIs.  I constantly fight a battle with myself in wanting to buy the ZAO IIs, but lately the prices have just gone through the roof for these supposedly “perfect” eyepieces.  You’re comments have cooled my “demons” for awhile.

[BillP]

I read somewhere awhile back, maybe on Barry Gooley’s website Kohkasi Kohi (yea, I probably spelled that wrong) that not very many manufacturers in Japan ever made 4mm Orthos because the lenses were so hard to make, hard to orient properly, and hold squarely in the eyepiece.  Maybe that is the problem.

I recall reading that also.  When I took apart my 4mm TMB Supermono it was astounding to me that those 3 cemented lenses could even be made!  Wish I put a ruler in this pic, but to give you an idea the cloth it is sitting on with those big holes in it is a microfiber lens cleaning cloth!!

 

[lylver]

 

that not very many manufacturers in Japan ever made 4mm Orthos because the lenses /.../

I did

 Aki-Saito-Ortho-Abbe.txt   7.56KB   39 downloads

here

https://www.cloudyni...rtho/?p=9812372

The 4mm had, at least, a 12.5° fully corrected (>0.95 polystrehl) off-axis field at f/9, this one was an Mittenzwey-Abbe engineered by Nikon.

I did only a reengineering try.

 

Thanks to Mr Onuma & Mr Nakamura from ScopeTech Co.

Excerpt from Aki Saito, former president of Vixen Optical Co., Ltd.

Difficulty of Abbe Ortho
Nowadays, the majority of eyepieces occupy the US 31.7 size and the Zeiss 24.5 type seems to continue to decline.

However, among them, only the 4mm ortho Abbe demonstrates its exceptional strength, and its power has not diminished in response to the hard eyes of all mania.
So, what kind of eyepiece is Abbe Ortho ?

"To measure the angular distances in the field of view of a telescope, you need an eyepiece with very little distortion of the image, for example, an orthoscopic eyepiece means orthoscopic, which means that it does not There is no distortion or distortion of the image.To do this, the imaging conditions must be met, although in practice there is an example where the name is orthoscopic, even if there is a distortion of the image. about 30% around the field of view.
Usually, what is generally referred to as an orthoscopic eyepiece has the structure shown in the figure. It was invented by the Abbe° in 1893. The usual design is that the field lens is a BK7-F3-BK7 and that the lens is a plano-convex lens with BK7. With this glass combination, the eye relief is about 78% of the focal length and the apparent field of view is 45 degrees inside and out.

Orthoscopic eyepieces are one of the best eyepieces and can be used for short focal reflectors such as F6 and F8. It is suitable for observation and high magnification measurements because it exhibits relatively little distortion, good achromaticity and reduced surface reflection. Low magnification lenses are not very easy because they are too thick. (Telescope optics, Shotaro Yoshida, Seibundo Shinkosha, S53 edition)
There are various orthoscopic types, such as the Abbe type, the Plössl type and the Ramsden achromatic type, which are sold taking advantage of their characteristics. Even in Vixen eyepieces, Abbe-type production is limited to this eyepiece of 24.5 4 mm and the reticle-scaled eyepiece OR-12.5 31.7, especially 4 mm if a special order is included.

In addition, 4 mm corresponds to a size of 24.5 cm and unlike the BT type, the selling price is extremely limited.
Why not re-examine Father Ortho, made by the best Japanese in the world, with 100% protection against German engineering design values? /.../

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Edited by lylver, 10 May 2020 - 06:59 PM.

[barbie]

I think the best current available Orthos made today are the Tak Abbe Orthos. I have from 9mm to 32mm focal lengths and they are all razor sharp. Don't know about their shorter focal length Abbes. If I need something higher than 9mm, I Barlow my 12mm Abbe or just use my Tak TOE's when conditions permit. The Tak Abbe Orthos Barlow very nicely.

Edited by barbie, 10 May 2020 - 05:38 PM.

[lylver]

And for information, the Clavé asym plössl do the same and exist as a 3mm work at f/8 better.

You can go with them down to f/5 but high strehl field decrease much. There is no problem to say Clavé had the skills to do them. They pattented a grinding and polishing patent.

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Edited by lylver, 10 May 2020 - 07:00 PM.