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Equipment Discussions >> Refractors

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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Are achromats enjoying a come back? new [Re: Joe Bergeron]
      #5537486 - 11/24/12 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?"



- Jim


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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: ken hubal]
      #5537535 - 11/24/12 05:00 PM

Quote:

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.

Edited by John Huntley (11/24/12 05:05 PM)


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Sean Cunneen
Let Me Think
*****

Reged: 08/01/07

Loc: Blue Island Illinois
Re: Are achromats enjoying a come back? new [Re: John Huntley]
      #5537597 - 11/24/12 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.

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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Are achromats enjoying a come back? new [Re: Sean Cunneen]
      #5537603 - 11/24/12 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.



- Jim


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Kentuckystars
member
*****

Reged: 03/17/08

Loc: Northern Kentucky
Re: Are achromats enjoying a come back? new [Re: jrbarnett]
      #5537632 - 11/24/12 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.

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Vondragonnoggin
Post Laureate
*****

Reged: 02/21/10

Loc: Southern CA, USA
Re: Are achromats enjoying a come back? new [Re: Kentuckystars]
      #5537721 - 11/24/12 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.


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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: Sean Cunneen]
      #5537801 - 11/24/12 08:29 PM

Quote:

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!


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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: WRAK]
      #5537926 - 11/24/12 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.

Alan


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la200o
Carpal Tunnel


Reged: 09/09/08

Loc: SE Michigan, USA
Re: Are achromats enjoying a come back? new [Re: Sky Muse]
      #5537964 - 11/24/12 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


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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: la200o]
      #5538039 - 11/24/12 11:23 PM

I believe this is correct.

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Lynnblac
super member
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Reged: 04/06/09

Loc: Arizona
Re: Are achromats enjoying a come back? new [Re: jrbarnett]
      #5538072 - 11/24/12 11:52 PM

Quote:


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.


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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: la200o]
      #5538077 - 11/25/12 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


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stanislas-jean
Carpal Tunnel


Reged: 10/22/08

Re: Are achromats enjoying a come back? new [Re: Lynnblac]
      #5538291 - 11/25/12 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


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Jeff B
Carpal Tunnel
*****

Reged: 12/30/06

Re: Are achromats enjoying a come back? new [Re: jrbarnett]
      #5538470 - 11/25/12 10:16 AM

Quote:

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?"



- Jim




Now that's just plain mean.

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


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: Are achromats enjoying a come back? new [Re: Lynnblac]
      #5538608 - 11/25/12 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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galaxyman
Vendor - Have a Stellar Birthday
*****

Reged: 04/04/05

Loc: Limerick, Pa
Re: Are achromats enjoying a come back? new [Re: jrbarnett]
      #5538672 - 11/25/12 12:37 PM

Are achromats enjoying a comeback?

Yes, but it started a while back when Skywatcher, Celestron, and Meade introduced a 6" refractor affordable to the common observer.

Higher end large achros from say D&G still and is fairly affordable, but they also required a more expensive massive mount with their longer focal lengths.

Now we've added into the mix Explore Scientific and AT large achros with upgraded optics (and coatings) and better mechanical offerings (focusers), which also can be easily transported with the mix of shorter tube and less massive mounts. The views through these scopes in dark skies are quite good, and yes the can be pushed (magnification) with all DSO's.

I own only achros for now, and have been quite pleased with the views...the 8" BIG TIME. The probability of them being replaced for an APO is possible (exception the 8"). I do not think a 4" APO could do much more then my current 4" f/10 achro for my needs (it's a particular good one). Most likely the 6" for say APM's new ED or something like it.


I agree with Jim that quality is essential, for I have seen personally the difference in a number of mass produced 6" achros, but overall they have given me quality views and nights, and that is what it's all about




Karl
E.O.H.


Chesmont Astronomical Society - www.chesmontastro.org
Galaxy Log - http://www.youtube.com/user/GalaxyLog4565?feature=mhee
Telekit (Swayze optics) 22" F/4.5 Dob
Homemade (Parks Optics) 12.5" F/4.8 Dob
TMB/APM 8" f/9 Refractor”The Beast”. One great DEEP SKY achro
ES 6" f/6.5 achro. Good one
Celestron Omni XLT 102 refractor.
Celestron 10x60mm Binos


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EddWen
Pooh-Bah


Reged: 04/26/08

Re: Are achromats enjoying a come back? new [Re: Sean Cunneen]
      #5538726 - 11/25/12 01:25 PM

I have nothing against achromats. My first scope (1956) was a home-made 2.4" f/20 lens from Edmund in a cardboard tube. Later built a 6" f/5 Jaeger lens combined with a surplus tank periscope eyepiece. Enjoyed them both, regardless the pipe mount.

Now I'm a fashionista owning 4" and 6" A-P apos. But I'm not alone.

Recently, Astro-Physics built a small run of 175 mm scopes with some old glass stock sitting on their warehouse shelves. Being subject to the heavy A-P advertising campaign, and the fashionable 4” focuser used, I was tempted to add my name to the “drawing” list for the last scopes from the production run. As usual, I procrastinated until too late.

Amazingly, more than 400 others listed themselves. I guess there are a huge number of misinformed people. The few names were drawn, but most were disappointed.

I’ll wager that these ~400 people know that a quality, long focus achromat can approach the performance of a short focus apo. But, they’re not standing in line for them.

There is no reason people that do not have a budget for other than achromats cannot use and enjoy them, but I don’t see the need, for some, to categorize those of us who can, as somehow being mislead, or lacking knowledge.


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orion61

*****

Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: Are achromats enjoying a come back? *DELETED* new [Re: jrbarnett]
      #5538988 - 11/25/12 03:45 PM

Post deleted by Scott in NC

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csrlice12
Postmaster
*****

Reged: 05/22/12

Loc: Denver, CO
Re: Are achromats enjoying a come back? new [Re: orion61]
      #5539057 - 11/25/12 04:32 PM

Then they can go over to look thru the real telescope that uses their refractors as finderscopes.......

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csrlice12
Postmaster
*****

Reged: 05/22/12

Loc: Denver, CO
Re: Are achromats enjoying a come back? new [Re: Kentuckystars]
      #5539063 - 11/25/12 04:34 PM

Quote:

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




Good selling tactic--Won "Best Scope Award" at the 1012 Goddard KY Star Party!


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