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Equipment Discussions >> Refractors

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Nippon
scholastic sledgehammer
*****

Reged: 10/22/09

Loc: Central Florida
Are achromats enjoying a come back?
      #5514165 - 11/11/12 09:52 AM

There seems to be a resurgence in interest in the achromatic scopes. If so what are some of the reasons do you think. I have a Vixen A 105 M. I bought it because I wanted a 4" scope with good optical figure for doubles and planets. The color correction is good and I'm pleased with it. But part of my reason was just the classic appeal of a good 4" inch achro.

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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Are achromats enjoying a come back? new [Re: Nippon]
      #5514200 - 11/11/12 10:25 AM


"There seems to be a resurgence in interest in the achromatic scopes."

Nah, it's just that the folks who normally haunt the Classics forum have finally discovered that there are other forums on CN.

I "get" achromats when a good one can be had at a given aperture for materially less money than a like-apertured ED doublet or triplet. Indeed when I bought my Antares 105/1500 it was just $650 and the competing 4" ED doublets from Synta were $900. What I don't "get" though is paying more for an achromat of a given aperture than you could pay for a decent quality RD triplet or doublet. Other than indulging one's curiosity, I feel there's little logic in such a move.

Regards,

Jim


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astroneil
Pooh-Bah
*****

Reged: 07/28/09

Loc: res publica caledoniae
Re: Are achromats enjoying a come back? new [Re: jrbarnett]
      #5514248 - 11/11/12 10:54 AM

Nippon,

They are indeed!

It's great isn't it?

Let me tell you why, in my opinion.

Apochromats are transitional technology.

There are innovations on the way that will allow flat lenses with perfect optical correction to be made cheaply. It will be scalable too.

See here for details:

http://www.seas.harvard.edu/news-events/press-releases/flat-lens-offers-perfe...



Apochromats will be phased out eventually.....like all other types of transitional technology.

Then, Nostalgic Man, suffering from a kind of poverty of the imagination, will seek out achromats above all other telescopic relics from the past. For these were the first kinds of refractors that were corrected well enough to give both an accurate and picturesque simulacrum of the heavenly bodies, as history so nobly attests to.

Achromats have a future (because they are the true gems in the box); apochromats don't.

Enjoy your Vixen achromat; one day it will fetch a whole lot more than a TEC, Tak or AP.

My two cents.

Regards,

Neil.

Edited by astroneil (11/11/12 09:24 PM)


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sg6
professor emeritus


Reged: 02/14/10

Loc: Norfolk, UK.
Re: Are achromats enjoying a come back? new [Re: Nippon]
      #5514291 - 11/11/12 11:24 AM

Possibly people are realising that a decent achro is a decent scope. If designed reasonably they can produce some good viewing at a reasonable cost.

Maybe the imaging side carried over too much into the visual side, as in imaging you cannot put up with CA. Whereas in visual some people simply don't worry about CA and on dim objects the CA may well not be noticable. Why pay 3-5x for something that is of no concern or relevance.

You will have to accept a longer scope and I would say there is a practical limit to length, guess about 1.2 metre focal length.

The available glass types are now more varied, perhaps manufacturers do not use an ED glass, but they might use one that is closer to ED then what was around 15-20 years ago. Still achro but better then previously available.


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dlapoint
scholastic sledgehammer


Reged: 08/18/03

Loc: Moncton NB Canada
Re: Are achromats enjoying a come back? new [Re: sg6]
      #5514343 - 11/11/12 11:54 AM

Refractors are illogical any way you slice it. So picking an achromat over an apo for dso observing is no more crazy than picking a refractor over a dob for said purpose.
If you want a 6 inch refractor and don't want to sell one of your kids to buy it, the achromat is the only game in town. You use your scopes for their intended purpose. Play to the strengths of the design and you will be happy. I just picked a 6" achromat and I'm having fun exploring many classic dso's that my other scopes just can't show off, like this scope. So yes I think they are, and should make a come back.


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Nippon
scholastic sledgehammer
*****

Reged: 10/22/09

Loc: Central Florida
Re: Are achromats enjoying a come back? new [Re: dlapoint]
      #5514433 - 11/11/12 12:51 PM

Well I like my Vixen achro well enough but fetch a higher price some day than a TAK or TEC??? I really doubt that. Now if you have a TAK or TEC that you want to swap to get my Vixen I'd be glad to help you out.

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astroneil
Pooh-Bah
*****

Reged: 07/28/09

Loc: res publica caledoniae
Re: Are achromats enjoying a come back? new [Re: Nippon]
      #5514504 - 11/11/12 01:47 PM

Quote:

Now if you have a TAK or TEC that you want to swap to get my Vixen I'd be glad to help you out.




No Sir, I don't own one of these kinds of instruments any more.

I gave the last one I had away. God knows where it is now.

Here's that story, with no regrets.

http://www.cloudynights.com/item.php?item_id=2765

I do however have a very nice 6" f/8 ED doublet on loan right now for an up-and-coming magazine review.

Kind Regards,

Neil.


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Astrojensen
Post Laureate
*****

Reged: 10/05/08

Loc: Bornholm, Denmark
Re: Are achromats enjoying a come back? new [Re: dlapoint]
      #5514543 - 11/11/12 02:07 PM

Quote:

Refractors are illogical any way you slice it.




I don't think so. They do have their niches, which they serve well. One thing they do better than anything else in my experience, is wide-field deep-sky observing. They also cool down quickly and so if you have only a limited amount of time for lunar-planetary observing, a refractor is the way to go. They are also superior for solar observing. Double star observing is also one of their traditional niches.


Clear skies!
Thomas, Denmark


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Sky Muse
sage


Reged: 10/26/12

Loc: De Soto County, MS
Re: Are achromats enjoying a come back? new [Re: jrbarnett]
      #5514576 - 11/11/12 02:29 PM

There are times when I miss my second telescope, a Parks 80mm f/11 achromat/equatorial. I gave it to a relative after acquiring the fluorite, along with a couple of oculars I considered expendable. With it, I once observed Venus from about five in the morning when it was still dark until the sun approached high noon, the planet's surface at that point appearing as sand, just visible, peppered, grainy, the mount motorised only in right ascension and positioned partly on the grass, partly on the walk at our home in midtown Memphis. Earlier, just before dawn, an unsuspecting fellow, known to be challenged, was walking down the sidewalk. As he approached, he suddenly caught sight of me, crouched down, peering through my refractor. He jumped back a bit, veered off the sidewalk, off the curb into the street, then back onto the path and resumed his walk. I'll never forget his startled expression, sustained for several moments as he passed, nor the face of Venus alight that morning in 1992.

That being related, I'm wanting another achromat, with said Antares f/15 appearing more and more desirable, especially with its Japanese doublet, if I'm not mistaken, and costing less than that of the Skylight produced in London.

Alan


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robboski2004
member


Reged: 01/14/08

Re: Are achromats enjoying a come back? new [Re: astroneil]
      #5514619 - 11/11/12 03:05 PM


Apochromats are transitional technology.

120 Years and counting !

Interesting comment Neil.

Regards.
Ian.


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Are achromats enjoying a come back? new [Re: astroneil]
      #5514637 - 11/11/12 03:16 PM

Technological advancement is absolute and does not grant exceptions. Just as the achromat replaced Galileans and Keplerians, the aprochromat has just as surely and irreversibly replaced the achromat. One day, something else will replace the apochromat, but by then the achromat will be as well represented in use as the Galileans and Keplerians are today. Know where a guy can buy a quality Keplerian these days?

There's nothing wrong with make-believe, of course. It can be fun. Who doesn't like dressing in Elizabethan garb, hefting a tankard in one hand and turkey leg in the other, and talking funny? But that doesn't signal a return to relevance of Elizabethan culture, fashion or speech mannerisms. It's just recreational "pretending".

Just as the achromat rendered the Keplerian and other singlets largely irrelevant, so too the apochromat has rendered the achromat largely irrelevant (in a commercial sense), and indeed something new will eventually relegate the apochromat to oblivion as well. But that's tomorrow. Today, the relevance of refractors is all about apochromats. Far more energy is devoted to making better aporchromats than any other refractor design presently.

In thirty years, the pretentious re-enactors will be using A-Ps, TECs and Taks, and find all kinds of justifications for clinging to those designs, other than technical superiority. Today, though, the refractor anachronists cling to achromats. But don't feel bad. You should hear what those Keplerian fanboys are saying about both achromats and apochromats!

- Jim


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stevew
Now I've done it


Reged: 03/03/06

Loc: British Columbia Canada
Re: Are achromats enjoying a come back? new [Re: Nippon]
      #5514652 - 11/11/12 03:26 PM Attachment (58 downloads)

Quote:

There seems to be a resurgence in interest in the achromatic scopes.




I didn't realize that they had left.


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7331Peg
Sirius Observer
*****

Reged: 09/01/08

Loc: North coast of Oregon
Re: Are achromats enjoying a come back? new [Re: Sky Muse]
      #5514655 - 11/11/12 03:32 PM

Quote:



. . . That being related, I'm wanting another achromat, with said Antares f/15 appearing more and more desirable, especially with its Japanese doublet, if I'm not mistaken, and costing less than that of the Skylight produced in London.
Alan




If you can swing it, Alan, go for the Skylight instead. I've had an Antares f/15 (actually f/14.3) and now have the Skylight f/13. The Antares did a pretty good job, but the views through the Skylight are much more crisp, and it will handle a whole lot more magnification than the Antares before the image starts to break down. The construction of the Skylight is much, much better, and the focuser is a huge improvement over the one provided on the Antares scope. I hesitated at the cost, but it was well worth it.


I never would have believed it if I hadn't seen it for myself. A well-figured achromatic lens is really something special. If you've ever looked through a Zeiss Telementor or the 80/1200 Zeiss, you'll understand what I'm referring to.

And you can dispense with the Elizabethan garb -- they only wear that in some strange area of California located north of San Francisco.


John


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Astrojensen
Post Laureate
*****

Reged: 10/05/08

Loc: Bornholm, Denmark
Re: Are achromats enjoying a come back? new [Re: jrbarnett]
      #5514671 - 11/11/12 03:42 PM

Quote:

Just as the achromat replaced Galileans and Keplerians,




The achromat hasn't replaced the galileian and keplerian telescopes, but improved them. The optical layout of the modern apochromatic telescope, with a positive eyepiece, is still, technically, called a keplerian telescope. Likewise, you can buy small achromatic galileian binoculars for use in theaters and operas or even as ultra-specialized 2.8x40 glasses for observing the milky way with 28° TFOV. There's a tremendous difference in their level of sophistication, but all modern telescopes and binoculars are based on the same basic optical principles Galileo and Kepler found.

Quote:

Know where a guy can buy a quality Keplerian these days?




Almost everywhere. Even shopping malls. OK, you said "quality", so maybe not shopping malls...

Quote:

the apochromat has rendered the achromat largely irrelevant (in a commercial sense)




No, not yet. Achromats still outnumber apochromats by a huge number. Think binoculars, spottingscopes and rifle scopes. Rarely are these apochromats and they outsell amateur telescopes by huge amounts.


Clear skies!
Thomas, Denmark


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robboski2004
member


Reged: 01/14/08

Re: Are achromats enjoying a come back? new [Re: jrbarnett]
      #5514675 - 11/11/12 03:46 PM

Quote:

Technological advancement is absolute and does not grant exceptions. Just as the achromat replaced Galileans and Keplerians, the aprochromat has just as surely and irreversibly replaced the achromat.

Jim,

At a guess ?? more achromats have been produced in the last 20 years, than the preceeding 300 ! So how they have been replaced with apos is an interesting assumption.

I know everyone is looking for the latest big thing !
Just like diffractive optics were going to make all other lens types obsolete 40 years ago , now we have this development.

Suggest we don't hold our breath !!

Ian.

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simpleisbetter
Carpal Tunnel
*****

Reged: 04/18/11

Re: Are achromats enjoying a come back? new [Re: robboski2004]
      #5514746 - 11/11/12 04:32 PM

To me it has to do with the economy. When I bought my AT-102ED it was affordable, the AT-111 was not, nor are the 106's or other triplets. When I bought my C6R OTA it's because I CANNOT afford or even think about a 6" in an ED doublet, let alone triplet. And being a visual observer only, CA isn't that big a deal. Today, if I were looking at a 4", the only choice for me would be an achromat since the ED's have all but disappeared and I can't afford the 4" triplets, especially for visual use grab-and-go.

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Sky Muse
sage


Reged: 10/26/12

Loc: De Soto County, MS
Re: Are achromats enjoying a come back? new [Re: 7331Peg]
      #5514793 - 11/11/12 04:58 PM

Hi John,

I, too, enjoy observing binaries and will take your advice in regard to the Skylight over the Antares. Thanks.

Incidentally, how often does the weather allow for clear nights there in the Northwest?

Cheers,

Alan


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Abb
super member


Reged: 11/19/10

Loc: Windsor Ontario Canada
Re: Are achromats enjoying a come back? new [Re: simpleisbetter]
      #5514805 - 11/11/12 05:08 PM

Well, I'd be very surprised if (e.g.) one could see (meaning "visually") the $1300+ difference between an ES 127 Achro and Apo if you had them side by side looking at (e.g) The Orion Nebula. No doubt the Apo would have drastically reduced CA if viewing the moon. How about the $???? difference between ES's 152 mm Achro and Apo.

I'll stick with my 2 Achro's for now....until I win a multi-million dollar lottery


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John Huntley
scholastic sledgehammer
*****

Reged: 07/16/06

Loc: South West England
Re: Are achromats enjoying a come back? new [Re: Abb]
      #5514972 - 11/11/12 07:29 PM

There is a resurgence of interest in achromats, thanks in part to Neil and his interesting writings, and companies like Skylight in the UK who are prepared to put them together very nicely, albeit for quite a few £'s.

Over the past 24 months I've been able to directly compare good 4" and 5" achromats with my Vixen 102mm F/6.5 and Skywatcher 120mm F/7.5 ED doublets and I've concluded that I won't be moving back (and that's how I see it) to achromats.

In short my ED's did everything the achromats did a little better and are much easier to mount steadily to boot.

My ED's are both older models so both cost me less than scopes such as the Skylight achromats and Antares 105mm F/15's.

It's good to find these things out for yourself though, if you can, and let the views you get be your guide


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rocketsteve
sage
*****

Reged: 04/17/11

Loc: Southeast Louisiana
Re: Are achromats enjoying a come back? new [Re: Astrojensen]
      #5515051 - 11/11/12 08:37 PM

Quote:

Quote:

Refractors are illogical any way you slice it.




I don't think so. They do have their niches, which they serve well. One thing they do better than anything else in my experience, is wide-field deep-sky observing. They also cool down quickly and so if you have only a limited amount of time for lunar-planetary observing, a refractor is the way to go. They are also superior for solar observing. Double star observing is also one of their traditional niches.


Clear skies!
Thomas, Denmark




It's almost like you read my mind.


I use my Sky-Watcher 80mm achro for solar, lunar and planetary viewing. I love the tack-sharp images that it produces and the focuser is butter-smooth.


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