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Equipment Discussions >> Refractors

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Mark Harry
Vendor
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Reged: 09/05/05

Loc: Northeast USA
Re: Are achromats enjoying a come back? new [Re: WRAK]
      #5536743 - 11/24/12 07:53 AM

Fact 7:
I've asked a question, and can't get an answer due to all the debate. Must be some truth to fact 6!
M.


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Pete-LH
sage
*****

Reged: 03/25/09

Loc: Wilmington, DE
Re: Are achromats enjoying a come back? new [Re: Kentuckystars]
      #5536864 - 11/24/12 09:20 AM

"Use the scope you have no matter what it is, it's the best scope in the Universe when your eye is to the eyepiece. Use Scope=Happy Astronomers"

This really is the key ...

My impression from threads like this is some of us(Me being as guilty or more than most) spend more time worrying about small differences in performance between scopes and more time looking at their scope than looking through the lens and studying Universe.

I have spent too much time and money searching for the next telescope and not enough time observing and sharing what can be seen ... shame on me!

That being said I just bought and I'm waiting to receive a nice used 90mm f/11 Achromat. Can't wait to compare it to my 60, 80, 90, 100, 102 and five inch refractors(None are short focust true APOs) as well as my two SCT's.

Actually some of the best sharp images I've viewed were through an f/8 C6R which was a great value and I let it go in search of a "better" refractor. For myself being red-green colour blind it makes less sense than for most here.


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PhilCo126
Post Laureate


Reged: 01/14/05

Loc: coastline of Belgium
Re: Are achromats enjoying a come back? new [Re: Pete-LH]
      #5536967 - 11/24/12 10:17 AM

Achromats didn't need to make a comeback... A 20 cm Comet Hunter refractor is a great way to enjoy a large refractor!


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vahe
scholastic sledgehammer


Reged: 08/27/05

Loc: Houston, Texas
Re: Are achromats enjoying a come back? new [Re: Kentuckystars]
      #5537033 - 11/24/12 11:00 AM

Quote:

Fact Four: I am not a doctor or lawyer, and it would be fair to say the same for many of us. In fact, I would say many of us have to watch our budgets in these times. Taking out a second mortgage to buy a scope does not make sense if you are on a budget, and maybe you do not want to save in the piggy bank for 5 years to get a scope. Then for average working folks like us that want a refractor (before we die) an achro fits the bill. And it will show us AT LEAST 90% of what an apo of the same aperture will show with decent quality optics on both sides.





Well, for starters you and I have something in common, me too, I am not a doctor or lawyer and as far back as I can remember I had to work on two jobs, a regular daytime and a permanent moonlight.

But the similarity end here, my first encounter with an apo happened about 25 years ago, a fellow member from our astronomy club had just bought a large Astro-Physics, this one was from pre ED era which is really not a real apo, but close enough.

I went for a look through that scope, there were no planets on the night, he had it pointed at some galaxies, next to the refractor he had his 10” Meade SCT pointed at the same object, what I saw in that refractor changed me forever, I could not get that image out of my mind until, years later, I bought a AP apo.

As for the Meade, it also changed my opinion of SCT’s, compared to the apo the SCT produced an image that to my eyes looked simply horrible.

Large apos are expensive and certainly out of reach for most of us “average working folks” but I know many average wage earners who sacrificed a lot and purchased one of these “designer” scopes, it is just how you prioritize your hobby, I am driving a 36 year old car, I am willing to sacrifice on that but when it comes to scopes my standards are a bit higher.

Vahe


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Are achromats enjoying a come back? new [Re: Kentuckystars]
      #5537089 - 11/24/12 11:31 AM

"Though a subject of much debate, the image of an apo will be slightly better then the image of a long focus achro."

This one is not a fact. If the APO has the better figure, it will produce the better figure. Color error is only one aberration that affects visual image quality. There are other figure-error induced aberrations that are considerably more damaging to the image than defocused light in particular wavelegths.

"Apo's are expensive, sometimes very expensive. Achro's much less so."

This one too, is not a fact. Because quality, and not design, is what is most important, and quality costs money, the best achromats are more expensive than the more modest apochromats. Basically, whether achromat or apochromat, you generally get what you pay for. There is no free lunch. There are any number of 4" apochromats that are less costly than a 4" Skylight long focus achromat. When Antares was still selling the long focus achromats using "Vixen Spec" optics, those scope typically cost a couple of hundred dollars *more* than FPL-53 ED doublets of like aperture.

I pretty much agree with everything else you wrote, though. Stephen Stills said it best - "Love the one you're with!"

Regards,

Jim


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Kentuckystars
member
*****

Reged: 03/17/08

Loc: Northern Kentucky
Re: Are achromats enjoying a come back? new [Re: jrbarnett]
      #5537118 - 11/24/12 11:47 AM

My "facts" were not meant as hard rules, more like general guidelines. There are always exceptions to the convention in this world, a "hard line" rarely exists with anything. The constant apo vs. achro debate gets on my nerves though.

You have to ask yourself: What kind of astronomer am I? One who studies the heavens, or one that spends much precious time studying opitcal quality.

I think I will keep looking up. Besides the pursuit of perfection is only an illusion. The closer you get the further you seem.


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Kentuckystars
member
*****

Reged: 03/17/08

Loc: Northern Kentucky
Re: Are achromats enjoying a come back? new [Re: vahe]
      #5537136 - 11/24/12 12:00 PM

I had an ED80 once, really liked it. But a period of unemployment forced the sell of all my equipment last year. I am currently employed and looking to enter the hobby agian when I get my money back from Uncle Sam in February.

All I have to use right now is an old Sears 60mm/700mm FL refractor. EP's stink but the objective seems to be of very good quality. I have ordered some better oculars for it but have been quite surprised at the detail seen on Jupiter. This scope is the reason I see little fault with a slow achro and why my new scope in a few months will be a long achro, just bigger. Budget is to tight for an apo, not that they are not great. But I have to get everything else too, just not room in budget for an apo. I am sure I will be happy though, looking at the Celestron Omni 102.


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Are achromats enjoying a come back? new [Re: Kentuckystars]
      #5537140 - 11/24/12 12:03 PM

"What kind of astronomer am I? One who studies the heavens, or one that spends much precious time studying opitcal quality."

Why not "both"? Particularly if understanding one helps facilitate and make more productive your pursuit of the other.

"Besides the pursuit of perfection is only an illusion. The closer you get the further you seem."

Thank goodness our Olympians don't think that way!

- Jim


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ThomasWos
super member


Reged: 02/10/07

Loc: Bellingham WA
Re: Are achromats enjoying a come back? new [Re: Kentuckystars]
      #5537163 - 11/24/12 12:16 PM

Quote:

You have to ask yourself: What kind of astronomer am I? One who studies the heavens, or one that spends much precious time studying optical quality.






Don't forget the title of this forum..."Cloudy Nights"!!!

I live where clear skies are rare, let alone clear skies with good seeing, (very rare indeed).

To me, an important part of my "study of the heavens" is learning more about optics and optical quality,
so that my precious observing time is as good as it can be.

Peace

Tom


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Kentuckystars
member
*****

Reged: 03/17/08

Loc: Northern Kentucky
Re: Are achromats enjoying a come back? new [Re: jrbarnett]
      #5537164 - 11/24/12 12:17 PM

I know enough to tell if my scope is collimated, and after that I can tell if the optical figure is within reason. I can't afford perfection so I don't expect it, I only expect to pass the quarter wave standard. Images will then be acceptable enough for my visual-only use.

Perfection is an illusion, it's part of our culture. Just when you think you have the best of something, something better comes along. Just when you think your the fastest runner, someone faster comes along and your history. The illusion of perfection is what drives athletes as well as industry.


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Kentuckystars
member
*****

Reged: 03/17/08

Loc: Northern Kentucky
Re: Are achromats enjoying a come back? new [Re: ThomasWos]
      #5537171 - 11/24/12 12:23 PM

I'm just saying, becoming obsessive over optical quality will eventually detract from one's enjoyment of the sky. It absorbs time and effort and then you get to a point where you can't be satisfied and always wanting something better. It's an expensive road and one I went down before (in better times). Like I said, enjoy the scope you have. I see you have a Takahashi, I think you have the optical quality issue solved.

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ThomasWos
super member


Reged: 02/10/07

Loc: Bellingham WA
Re: Are achromats enjoying a come back? new [Re: Kentuckystars]
      #5537226 - 11/24/12 01:15 PM

I know we're really getting off the topic, but I know what you mean about being obsessive.

It's been a long road of trying different scope designs and mounts, and selling them when they don"t match your present needs.
Unfortunately I can't really afford more than one setup so I've tried to maximize my rig into one scope.

Needless to say this involves compromises!

I would LOVE to have a long focus achro to study planets.

Tom


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EddWen
Pooh-Bah


Reged: 04/26/08

Re: Are achromats enjoying a come back? new [Re: Kentuckystars]
      #5537254 - 11/24/12 01:36 PM

I find it curious, people who appoint themselves as judges in the amateur astronomy community.

The community voraciously absorbs every scope that Astro-Physics and TEC can produce. The scopes are expensive. The buyers can be assumed to earn more than average. This usually requires a better than average education, and the intelligence to absorb and apply the education.

Yet some people suggest they buy these scopes because they listen to prattle, are fooled by marketing hype and for fashion.

Really ??

edit: not directed at kentuckystars

Edited by EddWen (11/24/12 01:38 PM)


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Are achromats enjoying a come back? new [Re: EddWen]
      #5537276 - 11/24/12 01:49 PM

Actually, the real irony is this. TEC and Astro-Physics (and for that matter Takahashi) really don't advertise. When was the last time you saw any of these makers use glossy print advertisements to promote their products?

It's the folks foisting lower end scopes on the public that advertise aggressively and delight in puffery. To wit...

"In the spirit of UNITRON. Refractors for a lifetime.

Refractors exist to produce higher power, high contrast images. The proliferation of high-element, lower f/ratio, ultra expensive designs may have snob appeal, but for true high power performance, focal length is KING! Don’t be fooled. ED refractors may have perfect color, but all the other aberrations remain. With high f/ratios, ALL the aberrations are at minimum. OTA pricing includes triple baffles, Elite achromatic objectives and 2-speed Crayford focusers."

"Now you can get a top performing apo triplet using the Stellarvue fully multicoated, triple tested apo objective. This star tested, state of the art apo triplet performs as well as the legendary Lomo objective both visually and photographically. And we have made this telescope lighter and more flexible with our larger and higher capacity 2.5” dual speed focuser."

"The Vixen A105M is a superior quality achromatic refractor. This 4” optical tube has excellent light gathering power and will deliver great views of the planets and beyond. With its magnesium fluoride coated objective lens, you will see stable, high contrast images."

"Here's one of our staff favorite telescopes that is especially popular with astrophotography enthusiasts, the 80mm apochromatic triplet Orion ED80T CF refractor telescope. With an 80mm aperture triplet objective featuring FPL-53 extra-low dispersion glass, views and captured images come through true to color and exhibit tack-sharp resolution.

Apochromatic refractor telescopes have a devoted following amongst amateur astronomers, for good reason. The crisp view offered by a high-quality apo refractor is truly a wonder to behold and share. Apochromatic refractors significantly reduce chromatic aberration, or false color, compared to standard achromatic refractor telescopes due to the use of "ED" (Extra-low Dispersion) optical glass and use of three optical elements. The visual and imaging benefits of apochromatic refractor telescopes have helped to make them instruments of choice preferred by many real-time observers and imaging experts alike."

And occasionally fans of cheap scope get in the act too...

"After several nights of testing on both the Moon and Jupiter, I found absolutely NO false color, photographically or visually. In fact, I was able to use magnifications several times more than that of the theoretical limit for an instrument this size. Also, mechanical capabilities and workmanship RIVAL that of Televue, Takahashi, and Astro-Physics refractors that I have owned and used.

Side-by-side comparisons show identical performance with these other high-end refractors. Personally, I have no stake in Astronomy Technologies. I bought this instrument with no preconceived notions or unrealisitic expectations. My current plans are to utilize the instrument for white-light solar work and for wildlife photography. Under excellent seeing conditions, I was able to use a magnification of 197X on Jupiter. The detail visible was nothing short of incredible!!"

It tends to be telescopes in which less effort is expended in figuring the optics or mechanical quality that instead invest in hyperbole laden marketing hype, and attract the brainwashed fanboy types. Both achromat and apochromat purveyors are guilty of this.

Regards,

Jim


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Lynnblac
super member
*****

Reged: 04/06/09

Loc: Arizona
Re: Are achromats enjoying a come back? new [Re: Abb]
      #5537309 - 11/24/12 02:20 PM


Quote:

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 $???? differencween ES's 152 mm Achro an




I agree, the main reason I kept my Orion 120ED over the Meade 127 Achro was the shorter tube.


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ken hubal
Pooh-Bah
*****

Reged: 05/01/07

Re: Are achromats enjoying a come back? new [Re: Lynnblac]
      #5537337 - 11/24/12 02:44 PM

Lynnblac's post seems to be THE ONLY accurate assement of why apos have become the new fashion statement. Long focus achro performance in a shorter tube. I also seem to recall that Thomas Back, who seems to be revered here among the apo crowd, stated in one of his essays awhile back that the main reason for apos is to attain a well color corrected image found in traditional long focus achros while keeping the tube length manageable. It would seem that this is the ONLY valid reason for such instruments to be made.

Another indisputable fact is that there have been no major discoveries made using apochromats, not a single one! Achromats, on the other hand, gave science its first fairly detailed views of the moon and planets. Another fact is that fast apos still have other Seidel Aberrations present in their design. Color correction isn't the only aberration that needs to be taken into consideration. Proof once again that apos have little more than fashion appeal to recommend them.
Kudos to Neil English for his work on making people aware of these and other often overlooked facts!

Clear skies old friend!

Edited by Scott in NC (11/24/12 03:30 PM)


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Joe Bergeron
Vendor - Space Art


Reged: 11/10/03

Loc: Upstate NY
Re: Are achromats enjoying a come back? new [Re: ken hubal]
      #5537405 - 11/24/12 03:38 PM

Another indisputable FACT is that no new continents have been discovered with motorized ships, only with sailing ships.

Ken, I'm afraid achromats gobbled up all the discoveries because achromats were all that existed when these low-hanging fruits remained to be picked. If you are implying that apochromats would have been incapable of matching these feats, you have truly left any semblance of reason far behind.

Edited by Scott in NC (11/24/12 03:43 PM)


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ThomasWos
super member


Reged: 02/10/07

Loc: Bellingham WA
Re: Are achromats enjoying a come back? new [Re: ken hubal]
      #5537433 - 11/24/12 03:53 PM

Quote:

Proof once again that apos have little more than fashion appeal to recommend them.






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Scott in NCAdministrator
80mm Refractor Fanatic
*****

Reged: 03/05/05

Loc: NC
Re: Are achromats enjoying a come back? new [Re: Joe Bergeron]
      #5537434 - 11/24/12 03:54 PM

Hey everyone, great discussion here on a very interesting topic. I'd like to remind everyone to please keep it respectful, though. Thanks!

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ukcanuck
Vendor (Skylight Telescopes)
*****

Reged: 11/07/06

Loc: London, UK
Re: Are achromats enjoying a come back? [Re: The Ardent]
      #5537456 - 11/24/12 04:06 PM

Quote:

This somewhat answers my previous question about refractors make in the UK, but there are more questions.

From reading the Skylight description, it looks very nice, but why are the lenses imported? Why is no one making objective lenses in the UK?

Last month I viewed thru a 6" f/15 refractor made by an amateur from North Carolina. Very nice views. It seems that all the American "boutique" refractors originated from an enthusiastic amateur telescope maker.




Hi Ray,

Regarding my choice of imported lenses...I will admit that my career path prior to my passion with Astronomy did not provide me with the optical fabrication skills to make a suitable lens with my own hands. With this in mind, I choose to outsource this to someone who does have these skills and equipment to do it for me. I have no problem with this model.

There are one or two private lens makers I know of in the UK who might do one-off lenses if their schedules allow, but I’m unaware of any optics houses currently offering volume in a made in the UK, astronomy suitable product, and while I did approach one or two in the beginning, the prices I was quoted for a small run were not workable for me. If this were not the case, then I would certainly look to the UK for optics.

Quote:

"Ultimately, to me the quality of the optics are key...and if it happens to be a long achromat tube, then so be it."

Richard, I couldn't agree more. At a given aperture, assuming rational design and choice of glasses, the refractor with the better optics will be the one that shows you more, fast or slow, apochromat or achromat. You can't go wrong with quality.

Regards,

Jim




Hi Jim, I’m sure we agree that optical quality is found in lenses and mirrors of all designs and is a base on which the telescope must be built...from there you can begin to appreciate what the design of the individual telescope can do, including the long Achromat. I would happily put one of my 4” long Achromats alongside any Apo for planetary or double star viewing. As you stated in a later post, it is not so simple to say that an Apo image is slightly better than an Achro. That's just not always the case.

In my opinion, Neil’s excellent work on his Stranger than Fiction essay shows that the Achromat is not only an overlooked instrument and why, but in some circumstances can provide a more pleasing image than an Apo.

To quote the Rembrandts; "That's just the way it is, baby"

Peace.


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