45 replies to this topic

[ASTERON]

Hi everybody
I need some
Does anyone have any information about or experience with the A&M 130 mm F/7 SuperApo Quarduplet (Astreya lens) with Carbon fiber Tube. This quadruplet lense is not a Petzval design but rather a pair of stacked air spaced gel cemented Doublets. This is a European made scope which is not available any more for sale.
A&M now sells only the 130mm F/6 or F/9 versions with TMB designed (LSOS) air spaced triplet in the same (or at least similar) CF tube.
My questions are:

1) Did anyone look through or have experience with the Quadruplet based scope.

2) If you do know about it what do you think about the pros and cons of the Quadruplet based scope Vs. the Triplet one ?

3) Any other thoughts or comments are desperately needed !

4) how would you rate these telescopes (both Quad and Triplet for Visual and AP purposes ?

5) Any takes about Tube current problems with Carbon Fiber Tubes in this specific scope or in general- will be greatly appreciated !

Thanks a lot for reading and commenting

Lihu

[ASTERON]

BUMP

[Erik Bakker]

Quadruplets are impossible to collimate/align outside the factory. Longer cooldown compared to triplets. My advice: for visual use f/8 or slower fluorite doublets, for AP triplets around f/6.

Erik

[ASTERON]

Quadruplets are impossible to collimate/align outside the factory. Longer cooldown compared to triplets. My advice: for visual use f/8 or slower fluorite doublets, for AP triplets around f/6.

Erik

Hi Erik,
Thats very interesting and useful observation - I didn't know about the colimation difficuly and the cooltime problem even though I suspected there would be some problem with a 4 Kg lens

Whats your take on the difference between the TV 127 petzal and the TMB 130 triplet ( primary use AP but also visual sometimes) Which one would you recommend as the best compromise

Thanks for your valuable comments.

Lihu

[KaStern]

Hello Eric,

Quadruplets are impossible to collimate/align outside the factory. Longer cooldown compared to triplets. My advice: for visual use f/8 or slower fluorite doublets, for AP triplets around f/6.

even tripletts are nearly impossible to collimate outside the factory.
Even if you have an interferometer it is hard work.

Cooldown depends on the mass of the glass and on if the lenses are airspaced
or cemented or oil spaced.

Wide airspaced tripletts take significant longer cool down time than
oiled tripletts with same aperture.

Everything has his pro`s and con`s

Using 4 lenses you theoretically can achieve better over-all correction.

Using a long focal length doublett makes things much more easy for
simply high mag observation.
But you loose the wide field option pro`s and con`s ....

Cheers, Karsten

[lukman]

Karsten, Which one cooldown faster, a Quadruplets or a triplet refractor?

[KaStern]

Hello Lukman,

Which one cooldown faster, a Quadruplets or a triplet refractor?

it depends...

- types of glas used
- thickness of the lenses
- airspaced or oil spaced
- lens-cell design
- lens-cell material
- tube material. Alu, steel, brass, gfk, cfk
- delta T

Clear skies, KArsten

[scope dog]

Quadruplets are impossible to collimate/align outside the factory. Longer cool down compared to triplets. My advice: for visual use f/8 or slower fluorite doublets, for AP triplets around f/6.

Erik

Hi Erik,
I'm glad you are sharing with us your very limited resource of knowledge about this lens.
The adjustment to the lens is no different than a air space doublet and not a triplet. Collimation the cell to the tube should have the push-pull 3 screw adjustment "IF astrotech has not removed that feature". If and accident occurs like dropping the scope well it just may need to be sent back.
Funny about cool down, "love these experts" The quad lens is design with more co stable glass then for example the SPL's. Greg Hartke explain during his CCD sessions "After focus, no adjustment was done from start to finish". In other words during change RBG focuse stayed the same.
Though more glass, but all have a close co. This is necessary
to keep the optical performance in range. If you use a Fluorite the CO is around 200 the crown is say 46. As this lens was design and adjusted for a shop temp of 75F. What happens when outside at 40F???? The crown shrinks some, but the fluorite shrinks a lot. What do you think happens to the performance of the lens?? gets better?
This lens is design by one of the top optical designers in the world. No one offers such a lens design and offers a
Chromatic shift under 68.

[ASTERON]

Quadruplets are impossible to collimate/align outside the factory. Longer cool down compared to triplets. My advice: for visual use f/8 or slower fluorite doublets, for AP triplets around f/6.

Erik

Hi Erik,
I'm glad you are sharing with us your very limited resource of knowledge about this lens.
The adjustment to the lens is no different than a air space doublet and not a triplet. Collimation the cell to the tube should have the push-pull 3 screw adjustment "IF astrotech has not removed that feature". If and accident occurs like dropping the scope well it just may need to be sent back.
Funny about cool down, "love these experts" The quad lens is design with more co stable glass then for example the SPL's. Greg Hartke explain during his CCD sessions "After focus, no adjustment was done from start to finish". In other words during change RBG focuse stayed the same.
Though more glass, but all have a close co. This is necessary
to keep the optical performance in range. If you use a Fluorite the CO is around 200 the crown is say 46. As this lens was design and adjusted for a shop temp of 75F. What happens when outside at 40F???? The crown shrinks some, but the fluorite shrinks a lot. What do you think happens to the performance of the lens?? gets better?
This lens is design by one of the top optical designers in the world. No one offers such a lens design and offers a
Chromatic shift under 68.

Hi Jim,
Are you also familiar with the 130 mm quadruplet lens ?
any comments you cam make regarding pro's and cons for your 152 Asteya or for the 130 mm quadruplet in a A&M carbon fiber tube for imaging would be greatly appreciated !

Thank you

Lihu

[Erik Bakker]

Hi Karsten,

Well said, I agree with you.

Clear skies,

Erik

[Erik Bakker]

Hi Jim,

Thanks for clarifying and corrercting me where I am wrong on the Astreya Quadruplet. My remarks where more generic then on the Astreya, which I have no personal experience with. From what you write I assume it is a superb lens.

As far as your remarks on the fluorite doublets in lower outside temeratures, I think in the smaller sizes, these differences in thermal expansion of the 2 elements don't become too offensive. All of my 3 fluorites give good images rather quickly.

Clear skies,

Erik

[scope dog]

Hi guys,
There are many forum post regarding this lens. Unfortunately
the relationship between Astreya and a vendor in europe is very poor and this vendor often post -. Enough said.
The SAPO evolved from a immersion doublet, singlet, singlet. To a immersion doublet, immersion doublet. To now a all air-space quadruplet. The are all either 152 or 130 F/7's. Th AM 130 F/7 is a immersion doublet,immersion doublet. The lens is highly corrected and is custom made.
The CF tube is really good looking and CF doesn't contract like aluminum, a very low CO. But being so doesn't conduct temp. So early setup to let the air get in I think is recommended. But my one friend with his 130 never did this.
However AM offered a vented model and that is neat. I believe the 130 offers a 32 degree image circle where no flatner is needed.
When Zeiss was making the superachromat to reach the level of correction for this camera a laboratory was required at a specific temperature. When the camera came out using a fluorite element " I think has 16 other elements total".
They figured how to keep the performance stable through out
working temp ranges and created the camera lens. By the way Superachromat is a copyright own by Zeiss. Superapochromat was coined by James Baker.
I had a FSQ 106, excellent scope, but hey If I drop that, now that is one scope not too many people can adjust. I guess that's why TN is in business. I also had a AP SF 152F/9 cemented triplet. A solid chunk of glass, no lens separation, no movement and no adjustment.

[Mike Clemens]

> I'm glad you are sharing with us your very limited
> resource of knowledge about this lens.

he stings!

Simple decision for me.... why choose a complex lens that vendors keep trying but evidently give up on, from a company who made the famous TMB180/9 that was so problematic to keep aligned.

TMB triplets may have the same possibility of alignment issues, but how often do you hear about it? And there are > 1000 of them out there.

Takahashi FSQ may be difficult to align when dropped, but isn't there local service for them in Europe, Asia and America. And how many Taks do you hear suffering from this?

I'm glad I found oil spaced triplets early on so I don't have to have these worries... buy a TEC140/7 and get on with it : )

[scope dog]

Immersion has it'e issues too. Tec Cracks
TMB 180F/9 Design by Dmitry Makolkin assisted by Tom Back, Made by LATMO and Mike that lens was not made by Astreya, nore design By Andrey. Andrey, was designing for Intes then before they broke up. He did make 2 or 3 180's within the past 2 years, but none to my knowledge prior. I don't know if that lens was your problem, but do I recall you had a issue a while back with some TMB triplet.

I recall person here from Germany posted about a immersion problem by a different manufacture too. However things do happen, so the
best thing is if the lens can be sent back for service in case. I do know service is not a issue with TEC, AP, Astreya, but I'm not sure with LZOS. If all optics were perfect this would be a different story, but they are not. Created by man imperfect by man.

[Mike Clemens]

> I'm not sure with LZOS

It was a BIG HORRIBLE issue for me....

I've heard of the TEC "cracks"... I am super careful to thermally accomodate the big TEC. That would be fearful.

[George Methvin]

I did not know Texas A&M even made a telescope..which end do you look throught.......

[scope dog]

This is the place web page
Not Texas.
Hi Mike,
I been through the mill also and I dealt with dead end dealers too. The important fact though is as good as the optical performance is the service that can be render.
I know TEC and Astreya are full service providers and there are others too I believe. But some lenses you need to go through channels and becomes quite difficult and expensive.

[Erik Bakker]

Here is what Dave Novoselsky has to say on the subject of Petzval designs elsewhere on Cloudynights:


"In another thread, there was some discussion of 'cheap' or inexpensive Chinese built Petzval designs. While I have not used them, I remain skeptical as their ultimate success.

I once owned the very first TV 140 sold to the public (Al Nagler kept, and as far as I know, still has the original scope.) I bought it in the secondary market for a reasonable price, and then shipped it back to Al for a 'tune up.' (It is since gone to a good home along with some of my other APOs when I thinned the herd a few years ago.)

My experience with the 140, and my conversations with Al regarding this and his later but smaller Petzvals educated me to the fact that this is an inherently difficult design to bring off well. Multiple glass surfaces, and the need to carefully align and fix the elements in the two sets of cells. This difficulty was confirmed in my discussions with the folks at Tak, who have two Petzval designs, the FSQ 106 and the Baby Q 85.

One would assume that since a Petvzal allows for an inherently shorter scope, and can be 'lengthened' visually by use of something like the Extender Q or Extender ED from and f/5 to an F8, without sacrificing the ability of the scope to function as both an astrograph and a visual instrument, and airline portable to boot, then one would have seen a slew of these designs and not limited, as of now, to 127mm.

Nope, the TV 140 was simply a bear to build, very expensive to produce, and needed a ton of handwork in fitting and testing. (And I have never seen Al allow anything to go out with the Nagler/Televue name on it that did not meet the highest standards of QC.) It was also sensitive to misalignment, as any Petzval is given the need to make sure all four elements are in their proper place. (Makes sense, a doublet is easier to design and build than a triplet with its extra two surfaces. Now consider getting two different sets of doublets aligned with one another and then aligned with a second lens cell down the tube. Easy to build? Hardly.)

If this appears to be a great design -- and it is -- then why are there not more of them around and why are they limited to relatively smaller aps? I spoke to one designer who said scaling up an existing 4" to 5 or 6" would result in a very, very heavy scope with some design and production issues. Going to a fifth element may make more sense optically, and might allow a 6" design, but the cost factor and the need for incredible care in assembly would result in a very high cost with the same issues Televue may have found in the sensitivity to misalingment.

Now, can a really good Petzval be mass produced? I doubt it. The Chinese have produced some remarkable scope recently, but they are focused on mass production. Petzvals do not lend themselves to mass production nor are they capable of being produced without a lot of hands on attention. The increased cost of the NP101 and 127 and the FSQ 85 and 106 over their conventionally designed and built half brothers is not gouging in an otherwise very competitive market. The reason is difficulty in assembly and QC. Ditto for like designs such as the Pentax line of astrographs. All of those elements take time to assemble and to align.

Can the Chinese do it via mass production? I would love to see that but right now, I remain a skeptic. This is a very competitive market. The benefits of the Petzval design and not a secret and not a newly-discovered concept. There is a reason Televue produced so few of the 140s and have not gone beyond the NP127. The NP127 is not priced where it is because Al is gready, look at the price of the Pentax 125.

The reason that the Petzval design has not 'flourished' is that fact that these designs are very difficult to produce and need a lot of attention when they are assembled and when they are tested. I just don't see mass production stepping up to replace the necessary hand fitting and assembly that is the hallmark of this design.

My opinion only and YMMV. Dave "


Spot on IMHO.

Erik

[scope dog]

This is the 5 element scope Andrey produced. I only know they produced 1. He also has plans for a 6" Petzval. When?
The SAPO is not a Petzval but very like the Tessar, basically model after, but larger. Also the Lichtenknecker VAS formula. Wolf has a thread on this.

[Mike Clemens]

5! The guy is certainly an artist with the glass.

[Catalin Fus]

Jim, isn't this scope the APO without any special glasses?

I hope I'm not mistaken :-)

BR
Catalin

[scope dog]

That 4" 5 element is the one, but still uses a flint. 102mm F/6.5 APO with large airspaces.
This APO made from ONLY ordinary glasses like K8 (BK7 Schott) and
SIMPLE flint glass! It's focus is 666mm, back focus - 433mm and total
track - 948mm. The length from front to rear lenses is 515mm. Color
Diffraction limited field is about 12mm (1 degree).
The large airspaces are not critical to temperature.
This design can go to 200mm in dia.

[chboss]

Hi guys interesting thread.

I was thinking of buying such a telescope from A&M but decided not to because of the long cooling time of the four lenses and that no feedback was available at that time. By now A&M no longer offers these Astreya lenses.

Back to the original topic, I found a test of such this exact type on a German site:
http://www.astro-for...read.php?t=6056
http://www.astro-for...27505#post27505

Cheers
Chris

[scope dog]

Hi Chris,
I had 4 large apo's, cool down never seem to be a issue unlike my 3 SCT's. By the time I finish setting up I was good to go. However over the years I began keeping my equipment outside. Thermal shock is something I'm more concern about then cool down time. Wolf is a great guy and
he has a ton of stuff on his forums.

[ValeryD]

That 4" 5 element is the one, but still uses a flint. 102mm F/6.5 APO with large airspaces.
This APO made from ONLY ordinary glasses like K8 (BK7 Schott) and
SIMPLE flint glass! It's focus is 666mm, back focus - 433mm and total
track - 948mm. The length from front to rear lenses is 515mm. Color
Diffraction limited field is about 12mm (1 degree).
The large airspaces are not critical to temperature.
This design can go to 200mm in dia.

This design is known for decades. Singlet objective with
multilens back corrector. Quite difficult to realize due to
large spaces and decentration problems.
This is the reason they are not common and exist only on a paper. Russians are going to try to realize this scheme because of lack of access to ubnormal glasses. Any properly designed triplet or even doublet using such simple ED glass as FCD1 or FPL51 will be much better choice.
If peoples have enough difficulties to collimate doublet (if it out of collimation for whatever reason) and practically are unable to collimate triplets (with very thin spaces), then what kind of difficulties they will experience if such a multielement scope will be out of collimation?!
One can ask Markus Ludes why he gave up with selling quadruplets. He will sure answers - decentration of elements.

Such design is even more difficult to align and collimate, than Petzval.