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Equipment Discussions >> Refractors

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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: Sky Muse]
      #5515150 - 11/11/12 10:03 PM

Back in 2003, fate blessed me, two-folded, with my first apochromat: a Takahashi FS-102 with a superb doublet, the front element being of calcium fluorite, a crystal rather than glass, and a rear element of low-dispersion glass(ED?). One way in which it was fortunate, it was on sale at the time for $1899, down from $2200 or so. Then, later, in 2006 or '07 with the beginning of the rise in cost of calcium fluorite blanks, it was replaced by the current TSA-102, a triplet(crown, ED, flint or crown?). No matter, for the FS-102 is decidedly superior given it's a tad brighter, with better contrast and sharpness, however in exchange it does exhibit slightly more spurious colour on brighter objects, though just slightly. I'll take the before-mentioned advantages instead.

The current four-inch triplet is described within advertisements as a "New Design", perhaps a ploy designed to mask Takahashi's necessary exodus from true fluorite, however Takahashi still produces fluorite elements, but only in 60mm and 90mm sizes, and then skips to this leviathan...THE FET...

http://www.takahashi-europe.com/en/FET-300.php

...all the scope you'd ever need, and then some.

Imagine all the used four-inch Takahashi fluorite refractors on sale in this ad or that, right now, with perhaps many of the sellers patently oblivious given the above, unless they're selling to acquire a larger one, whether it be an FS-152 or the astronomically-priced TOA-150, the latter a non-fluorite but optically excellent nonetheless in comparison to the former, though not nearly as aesthetic in that it is an evolution beyond pomp and circumstance.

Get them while they last, before someone else gets a clue...

On the other hand, there's just something about a plain and simple, good, old-fashioned crown and flint achromat that beckons. I can't explain it, as it's ineffable, or perhaps it's the child seemingly lost in all of us, regardless of technological advancements and monetary considerations; Elizabethan ruffs even, which I would sport in a heartbeat, but only on Halloween or in a past life.

Alan


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photiost
scholastic sledgehammer
*****

Reged: 12/14/06

Loc: Montreal, Canada
Re: Are achromats enjoying a come back? new [Re: rocketsteve]
      #5515170 - 11/11/12 10:13 PM

When I was 12 years old my first telescope was a 60mm Towa refractor.

I now own a few refractors the largest being 150mm

Yes with low cost Objectives coming out of China and recently some of the better ones from Japan, USA ..etc can be purchsed at "reasonable" prices I believe they are making a comeback.
-


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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: photiost]
      #5515207 - 11/11/12 10:30 PM

My first telescope was a 60mm Sears "Discoverer", when I was 7 or 8, and the first view was of Saturn through the recently-restored 20mm Kellner pictured within my avatar. Saturn appeared very sharp, though in a weird, fluorescent shade of green I'll never forget.

We've come a long way.


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rocketsteve
sage
*****

Reged: 04/17/11

Loc: Southeast Louisiana
Re: Are achromats enjoying a come back? new [Re: Sky Muse]
      #5515251 - 11/11/12 10:53 PM

My father bought my mother a brand new Meade Model 285 Refractor for her birthday when I was in my mid-teens, and paid WAY too much money for it. Looking through the 25mm M.A. EP produced decent lunar views, but when I placed the cheap, cheesy 9mm EP into the diagonal, for a high-power view, the moon looked like it had a severe case of the chicken pox. Needless to say, I was hooked, but it would be another decade before I would have the disposable income or time to pursue this hobby.

Refractors and EPs sure have come along way since the late 70s...


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chboss
professor emeritus


Reged: 03/24/08

Loc: Zurich Switzerland
Re: Are achromats enjoying a come back? new [Re: rocketsteve]
      #5515417 - 11/12/12 01:24 AM

Interesting and enlightening read....

I am sure the achromats will stay around as cheap alternatives for a long time to come, in my view they never left the amateur scene!
They will still be sold as entry level telescopes or for aficionados that are ready to spend more on hand figured achros with long focal lengths.

But let's be honest the market place has changed with the relatively cheap and always improving ED's out of China. Better color correction with shorter easier to mount tubes are hard to pass - especially when available on the used market.

I personally do not plan to go back to my first and second scope which were 70mm and 100mm Achros by now I am spoiled by more capable APO's!

best regards
Chris


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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]
      #5515453 - 11/12/12 02:28 AM

Quote:

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




The observing weather in the northwest -- well to put it politely, from about the middle of November of last year until now (geez, already a year), it's been fickle and uncooperative. Prior to that, I could almost always find at least a few hours of clear skies a couple of times a week.

I'm on the Oregon coast, so I get more cloudy nights than say the Portland area or Seattle/Tacoma, but even taking that into consideration, the periods of clear skies were frequent enough that I didn't suffer from photon deprivation.

I keep thinking this streak will end soon, but then I've been thinking that for about the last eleven months, too. Can't last forever . . . . . . can it?

If you're seriously interested in the Skylight 100mm, I did a review of it that was published in the March/April 2012 issue of Astronomy Technology Today. If you don't have access to the magazine, the un-edited version is available here.

After almost a year's experience with it, I'm still convinced it is truly a remarkable 100mm refractor.

John


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stanislas-jean
Carpal Tunnel


Reged: 10/22/08

Re: Are achromats enjoying a come back? new [Re: chboss]
      #5515562 - 11/12/12 07:27 AM

It's always a price question.
An excellent 100mm apo will cost more than a respectable 150mm achromat well designed and well corrected, free of aberration and injurements.
The 150mm in spite of the 100mm apo colorless will do always more even on planets.
Apart the dimensions fact, this should be a matter of interrest and selection for an observer who wants something in his hands. For lot of reasons.
Make Venus and Mercure in daylight, Mars with a simple light yellow filer, jupiter as well, saturn as well and Uranus too. Visually.
You will see the big differences between the 2.
Now try to find this kind of acurate doublet: old TMB achromat, DGO, Istar, old Clavé, etc...
The vixen 102mm achromat, the antares serie 102mm will do the same job visually than the 100mm apo even prestigious.
Think apo above 130mm to get a step sensitive for the 150mm, relative, but above a great step, for bankrupcy also.
Reason why people goes to 8-10" with perfect optics and this out perform the 130 apo, any, just equals the 150 apo for the 8" newtonian in terms on contrasts, resolution remains for the bigger.
All these scopes can be moved on average mounts.
If you think ccd go to apo or newtonian and any compact costless, even achromats well filtered.
Stanislas-Jean


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Jeff B
Carpal Tunnel
*****

Reged: 12/30/06

Re: Are achromats enjoying a come back? new [Re: stanislas-jean]
      #5515753 - 11/12/12 10:47 AM

Well Barry's backlog at D&G has gone from 1 to 2 years so I guess that says something about achro-popularity.

Funny, thinking about it, over the last 50 years I've been in the hobby, I've never been without a 3 inch or larger achromat.

Jeff


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Zamboni
scholastic sledgehammer
*****

Reged: 01/03/05

Loc: Colorado Springs
Re: Are achromats enjoying a come back? new [Re: Jeff B]
      #5515944 - 11/12/12 12:41 PM

Achros started their comeback when the first truly surprising Synta refractor hit the market as the C102 HD. Even though Chinese APOs are getting cheaper and better, there will always be a market for achromats when there are scopes like the Omni 102 around. Even taking into account CA, the optics are impressive by any standard and it's a well built "complete" system for under 500.

Achros will always be around as a good "stepping stone" for people getting into refractors.


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stanislas-jean
Carpal Tunnel


Reged: 10/22/08

Re: Are achromats enjoying a come back? new [Re: Jeff B]
      #5515953 - 11/12/12 12:45 PM

I started with the 3" unitron and now owns a 102 vixen and a 150mm istar. Results are excellent. I was on a 100ED and a 110ED that were not on the level in comparison.
Also a 200 newtonian from astrola and the 250 from orion uk that were excellent but also big.
For the compacts there was only the OMC 250 that was excellent and some DK difficult to hold in perfect alignment.
Get look in prestigious apo for comparison and found even with stronger contrasts the data collected are not more in quantity and not finer.
The long achromat get better images because in elevation with regards to the ground proximity. That makes mostly better results over a long time use.
Stanislas-Jean


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rwiederrich
Goldfinger
*****

Reged: 11/17/05

Loc: Always Dark skies of Belfair W...
Re: Are achromats enjoying a come back? new [Re: chboss]
      #5515977 - 11/12/12 01:05 PM

Quote:

Interesting and enlightening read....

I am sure the achromats will stay around as cheap alternatives for a long time to come, in my view they never left the amateur scene!

Chris




Actually Chris, Achromats enjoyed many years as professional instruments. Currently, refractors of any kind are not used by the professional..but by amateurs... APO's included.

Reflecting or compound designs are scopes of the professional these days.

Rob


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rwiederrich
Goldfinger
*****

Reged: 11/17/05

Loc: Always Dark skies of Belfair W...
Re: Are achromats enjoying a come back? new [Re: Jeff B]
      #5515992 - 11/12/12 01:16 PM

Quote:

Well Barry's backlog at D&G has gone from 1 to 2 years so I guess that says something about achro-popularity.

Funny, thinking about it, over the last 50 years I've been in the hobby, I've never been without a 3 inch or larger achromat.

Jeff




Comeback comes with a financial restriction as its cause sometimes. Less free cash around in personal accounts causes this kind of influx. Folks getting to enjoy a quality achro because of economy..where they may never have had the chance in a better economy.

I know for a fact most folks who look through my 6"f/15 or the 10"f/15 never in their wildest dreams thought the views could have been so magnificent. Cheap short achro's have falsified their impressions. A good quality long focus achromatic refractor can change that impression quickly....

Rob


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Are achromats enjoying a come back? new [Re: Abb]
      #5515995 - 11/12/12 01:18 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."

That's a very good point. The answer, however, depends on the quality of the two scopes and the magnification you're operating at in each. If the quality of each were indeed equal and the baffling of each identical, I think you'd be right. If, however, one had better optics and/or better baffling than the other, and you were operating a a non-trivial magnification (100x+), I suspect the better quality scope might show you more. Specifically it would likely show you Trapezium E and F more of the time than the poorer quality/poorer baffled scope.

There is no guarantee of quality with any mass-produced refractor, apochromat or achromat. However, the economics favor getting a better quality apochromat than achromat. Why? Apochromats sell for considerably more than like aperture achromats. This typically provides the manufacturer with larger per unit margins. Since optical quality is directly linked to time spent figuring and testing the optics, and time is money, the apochromat provides a larger budget to use in producing the optics. Of course, there's no guarantee that the apochromat maker doesn't instead put that extra margin in its pocket, but in the case of the achromat, that margin doesn't exist and there's little chance that the maker will spend more making the optic than they sell it for.

That extra margin in the case of the apochromat also typically translates into more and better OTA features and accessories, so in that regard too, you might notice a difference (better focuser for example).

There's absolutely nothing wrong with achromats. They can be lovely scopes and more often than not offer great value (capability per dollar). That said, their days as serious commercial astronomical instruments are numbered, IMO. Trickle down is a product of progress and innovation. Eventually it will become as cheap or cheaper to make apochromats as achromats. When that happens, even the price/value advantage will vanish I suspect.

In other words, soon you won't need to win the lottery - you'll be buying 5" ED triplets for the same price you pay today for a 5" achromatic doublet.

Regards,

Jim


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stanislas-jean
Carpal Tunnel


Reged: 10/22/08

Re: Are achromats enjoying a come back? new [Re: jrbarnett]
      #5516125 - 11/12/12 02:34 PM

If we follow your post that means for the same amount we will get an apo of same 5" aperture.
This could be but with regards to the optical acuracy this will involve something just average with such cn apo.
This was my edventure with the 100 and 110ED, colorless but just average strehl, washed on small features that achros showed conspisciously.
The better example was Venus featureless into that apos.
Chromatic aberration is not the only link for serious results, visually.
Stanislas-Jean


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LivingNDixie
TSP Chowhound
*****

Reged: 04/23/03

Loc: Trussville, AL
Re: Are achromats enjoying a come back? new [Re: stanislas-jean]
      #5516195 - 11/12/12 03:20 PM

I have been in this hobby for a long time. A long time ago if you wanted a refractor it was either Astro Physics, Tak or TV. Orion also sold some rebadged Vixen stuff. Those were the choices then, Astro Tech didn't exist and SV was just starting with their 80mm scope that got some interesting reviews.

Then one day the 80mm Apo from Orion showed up and changed everything.

Today you can buy a nice refractor for a fraction of what they cost a decade ago. So I would say yes Achros are having a comeback and Apos are in a golden age!


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AstroSteve
scholastic sledgehammer


Reged: 08/17/04

Loc: Kissimmee, Florida
Re: Are achromats enjoying a come back? new [Re: rocketsteve]
      #5516264 - 11/12/12 04:02 PM

I have owned some nice WO ED refractors and they served me well. I own a AT72ED and love it but for visual I just love my Orion ST120 on a Versa-Go II alt-az setup. simple easy to pick up from the garage to the driveway or backyard. With some good EP it's just a delight to own and the contrast on DSO is just wonderful. The Plaides is my favorite this time of the year to view.

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KaStern
scholastic sledgehammer
*****

Reged: 04/18/06

Loc: InTheDark
Re: Are achromats enjoying a come back? new [Re: Nippon]
      #5516289 - 11/12/12 04:22 PM

Hi folks,

Quote:

Are achromats enjoying a come back?




no. Achromats are outdated.
You can build an ED-refractor for a small additional money.
Wat do you need?
Tube: Same cost
Lens-cell: Same cost
Focusser: Same cost
Polish and figure: Same cost
glass: Additional cost.

Cheap chinese ED glass will be more expensive than typical low-cost Flint and BK7,
but it will not cost much more. Add 100 USD to the cost of an 5" achromat.
If both are 5" f/10 the ED will easily outperform the achromat because the ED has much significant colour fidelity.

Cheers, Karsten


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Are achromats enjoying a come back? new [Re: stanislas-jean]
      #5516299 - 11/12/12 04:33 PM

Actually that really doesn't follow. Capital investment in optical fabrication and design is being made in designs that employ low dispersion glass types. "ED glass" is the new "fact" that the industry is assimilating. It is becoming plentiful and relatively inexpensive due to the large scale investment in its fabrication.

This availability of new materials, in turn, pulls investment in equipment optimized to mass-produce optics employing this new material. No one is making large scale equipment investment in computerized grinding and polishing machines for purposes of making C-F achromats. The ED 80 that essentially crippled the small achromat market that had been thriving before its arrival, was a creature of massive investment by Synta in the finest Zeiss optical fabrication equipment. These machines can turn out 1/5 to 1/7 wave ED doublet optics in an endless stream in apertures from 80mm to 120mm. With virtually no investment in modernizing the toolings for achromats (due to low demand) such optics require more hand work and therefore (aside from the cost of materials) are actually more costly to make than ED optics produced with a high degree of automation.

Typically hand-figured achromats from the 50s, 60s and 70s, when tested with an interferometer, on average weren't as well figured as mass-produced ED optics made by robots at the end of the last century. There are exceptions, of course, but I've seen many a 4" Unitron with suspect optical quality. The handful of Clark refractors I've seen bench test data for came in right around 1/4 wave.

Not only is fabrication more consistent and reliable today, but also testing is more accurate and precise too.

Regards,

Jim


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Mark Costello
Post Laureate
*****

Reged: 03/08/05

Loc: Matthews, NC, USA
Re: Are achromats enjoying a come back? new [Re: KaStern]
      #5516376 - 11/12/12 05:32 PM

Just what fraction of owners build their own refractors??

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mikey cee
Postmaster
*****

Reged: 01/18/07

Loc: bellevue ne.
Re: Are achromats enjoying a come back? new [Re: Mark Costello]
      #5516525 - 11/12/12 06:57 PM

I'm emphatically stating that I've not never had one to come back to! Mike

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