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Are achromats enjoying a come back?

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#251 Kentuckystars

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Posted 24 November 2012 - 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.
 

#252 ThomasWos

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Posted 24 November 2012 - 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
 

#253 EddWen

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Posted 24 November 2012 - 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
 

#254 jrbarnett

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Posted 24 November 2012 - 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
 

#255 Lynnblac

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Posted 24 November 2012 - 02:20 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 $???? 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.
 

#256 ken hubal

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Posted 24 November 2012 - 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. :grin:
Kudos to Neil English for his work on making people aware of these and other often overlooked facts!

Clear skies old friend!
 

#257 Joe Bergeron

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Posted 24 November 2012 - 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.
 

#258 ThomasWos

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Posted 24 November 2012 - 03:53 PM

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


:funny:
 

#259 Scott in NC

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Posted 24 November 2012 - 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!
 

#260 ukcanuck

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Posted 24 November 2012 - 04:06 PM

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. :ubetcha:

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. :cool:

"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. :undecided: 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. :bow:

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

Peace. :rainbow:
 

#261 jrbarnett

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Posted 24 November 2012 - 04:32 PM

Actually, there's a silver lining here, Joe.

The next time I'm showing the guy next to me who has a 6" f/8 achromat, Sirius B in my TEC, I can console him.

"Aww, don't take it so hard! My scope has all kinds of Seidel aberrations that yours doesn't. And your scope has a design that was responsible (shortly after the dark ages) for all kinds of discoveries. Not one single major scientific discovery has been made with a TEC. Want to have another look at Sirius B?"

:grin:

- Jim
 

#262 John Huntley

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Posted 24 November 2012 - 05:00 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.....


That seems a pretty good reason to me. I don't actually want an unmanageable scope.

I have compared my ED102 and ED120 refractors to good achromats of the same aperture, including a Skylight 4" F/15, and I'm happy that I'm not loosing any performance.

The mounting requirements of an F/15 4" or the F/17 4.7" that would match my ED120 would make ownership of such scopes, for me, impractical and somewhat expensive whereas my ED's sit very solidly on an AZ-4 and Giro-type alt-azimuth mounts on regular steel tubed tripods and can be quickly deployed and moved around my garden.

Getting great performance from scopes which are much less demanding to mount well is quite a significant step forward to me :)

And definitely not a "fashion statement" as my ED scopes are 12 and 7 years old, respectively. They both cost less than half as much as a new Skylight 4" F/15 too.
 

#263 Sean Cunneen

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Posted 24 November 2012 - 05:47 PM

I've arrived a bit late to this party but let me add this observation: You can go to a star party and have a look through an Achromat. Not so with the APO's, they always have some monstrosity of cameras, filters and other doo-dads attached. How is a guy supposed to do a comparo if the APO guys are always when hunched over their laptops, blocking up the focuser tube with that electro-junk? I think they do that on purpose, they are afraid of the truth.
 

#264 jrbarnett

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Posted 24 November 2012 - 05:49 PM

It depends on the star party I suppose.

At our star parties the cameras are attached to the R-Cs and the apochromats have diagonals installed.

:grin:

- Jim
 

#265 Kentuckystars

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Posted 24 November 2012 - 06:21 PM

Here at the Goddard, KY star party I'm the only person there. Guess my scope is the best on the field. :smirk:
 

#266 Vondragonnoggin

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Posted 24 November 2012 - 07:18 PM

I like short focus achromats. Mine made a comeback in my backyard the last clear night I had around here. 5 inches of beautiful views with my semi-apo in place as usual until I took it out to get to 300x on Orion's nebula.

Jupiter with a 1mm exit pupil was superb and after a 6 month hiatus observing, I could not believe the great detail, steady view, snap to focus, ease of setup on my ES AR127.

Love the achromat even at short focus lengths. I can do widefield, I can do planets, I can do clusters, I can snap my camera on it and shoot some photos. Need a binoviewer for it, but that's just icing on the cake.

Good value on a limited budget has made a comeback. All this other junk in the thread is just personal preference pickiness.

Someday maybe I might go down the apo road, but for now I don't have any complaints.
 

#267 Joe Bergeron

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Posted 24 November 2012 - 08:29 PM

I've arrived a bit late to this party but let me add this observation: You can go to a star party and have a look through an Achromat. Not so with the APO's, they always have some monstrosity of cameras, filters and other doo-dads attached. How is a guy supposed to do a comparo if the APO guys are always when hunched over their laptops, blocking up the focuser tube with that electro-junk? I think they do that on purpose, they are afraid of the truth.


Not always. I usually set up an apochromat at public outreach events. Thousands of people have looked through mine. The ignorant masses rave about what they see, and ask me why the views are so much better than what they see in other nearby scopes. The fools! If they only knew how much better their experience could be, if only I had an achromat!
 

#268 Sky Muse

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Posted 24 November 2012 - 10:07 PM

"Achromat schmachromat...apochromat schmapochromat", as a wiser child would utter...

As long as one views directly, via a lens, face to face before the ancients, instead of hiding around a corner as a criminal sporting a mirror in the vain attempt to spot a bobbie just up ahead, so he thinks, while all the while the officer is standing right behind him. The criminal turns, and comes face to face with his destiny...

...the refractor, heedless of design. :slap:

Alan
 

#269 la200o

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Posted 24 November 2012 - 10:31 PM

A curious thought occurs to me:I wonder if the apochromat is responsible for bringing the achro back. Refractors were kinda all but dead for awhile there, with everybody using SCT's and Newts; then comes the apo, reawakening interest in refractors. . . but they are so expensive . . . so why not the next best thing, an achromat? Just a thought.

Bill
 

#270 Joe Bergeron

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Posted 24 November 2012 - 11:23 PM

I believe this is correct.
 

#271 Lynnblac

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Posted 24 November 2012 - 11:52 PM

Actually, there's a silver lining here, Joe.

The next time I'm showing the guy next to me who has a 6" f/8 achromat, Sirius B in my TEC, I can console him.

"Aww, don't take it so hard! My scope has all kinds of Seidel aberrations that yours doesn't. And your scope has a design that was responsible (shortly after the dark ages) for all kinds of discoveries. Not one single major scientific discovery has been made with a TEC. Want to have another look at Sirius B?"



Sirius B was discovered with an achromat.
 

#272 Sky Muse

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Posted 25 November 2012 - 12:00 AM


The refractor then the reflector are the original designs from which the hybrids arose, a cobbled-togetherness of their unsuspecting parents. The Schmidt and Maksutov reflectors quickly came into their own, heralding the "great abandonment" in a woefully vain attempt at replacing the refractor, then the long-focus achromat, with many finding the new designs not only just that, novel, but in addition to providing quite satisfactory views with shorter tubes, though forever sacrificing the integration of a two-inch ocular into the optical train, "Who wants a two-inch or greater hole drilled through their primary?" The Questar Maksutov reflector was, and perhaps is still the greatest attempt among its kind.

Then came the apochromat, but never intended to forget its lineage.

Alan
 

#273 stanislas-jean

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Posted 25 November 2012 - 05:27 AM

Sure Sirius B will not appear at the 1st look.
But we know it is here that simplifies the research. This remains possible to get the 8.5 mmagnitude companion of Sirius in a 4" achromat as the vixen with 200x. A light yellow filter can help to get the data. This is better in an apo, but the data is collected and depend on the scope quality (optical acuracy rather than the CA).
We should try in a 3", will try with the unitron and 200x.
Other examples should be taken for the comparisons (suggest ones: the netpatch rifts on the martian polar cap last opposition, venus clouds, uranus banding).
I think for apo think ccd.
Stanislas-Jean
 

#274 Jeff B

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Posted 25 November 2012 - 10:16 AM

Actually, there's a silver lining here, Joe.

The next time I'm showing the guy next to me who has a 6" f/8 achromat, Sirius B in my TEC, I can console him.

"Aww, don't take it so hard! My scope has all kinds of Seidel aberrations that yours doesn't. And your scope has a design that was responsible (shortly after the dark ages) for all kinds of discoveries. Not one single major scientific discovery has been made with a TEC. Want to have another look at Sirius B?"

:grin:

- Jim


Now that's just plain mean. :roflmao:

However, if that cheap achromat had a Chromacor attached to it ............then you could both invite the C14 owner over so he/she could actually see Sirus B that night.

Jeff
 

#275 jrbarnett

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Posted 25 November 2012 - 12:00 PM

Indeed it was. A large one. And a very high quality one. And a very, very expensive one. Purchased for professional use at an academic institution. But not with a cheap, small one, built to a price, using mass production techniques.

Many, many times 6" achromats have failed to show what 3" and 5.5" triplet apochromats showed easily, same night, same site. But I don't think it's a design thing (achro versus APO). Rather I think it's a quality thing. Scopes with fatter margin for the maker allow for better QC, better R&D, better mechanical execution, etc., and that extra investment shows at the eyepiece.

- Jim
 






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