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Equipment Discussions >> Refractors

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drollere
Pooh-Bah

Reged: 02/02/10

Loc: sebastopol, california

history of the apochromat refractor new

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#5471246 - 10/15/12 10:39 AM

what is the origin and main development of the apochromatic refractor?

the achromatic lens combination was teased out by dollond, in part on a hint from hall's lenses, but it did not really get launched at large apertures until fraunhofer's dorpat telescope in 1824 and its 1835 twin for berlin.

to my knowledge, the apochromatic telescope evolved around the turn of the 20th century out of work on microscope, and then photographic, lenses. its adoption may have been inhibited by the desire to maximize transmittance for photographic purposes, as emulsions were slow.

who developed the major apochromatic designs, and when? what was the first large (> 25 cm) apochromatic telescope? what is the largest apochromatic instrument? when did apochromats first enter the amateur market? is roland christen the al nagler of apochromats?

a pointer to references, or your own summary of the tale, will be much appreciated.

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vahe
professor emeritus

Reged: 08/27/05

Loc: Houston, Texas

Re: history of the apochromat refractor new

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[Re: drollere]
#5471328 - 10/15/12 11:20 AM

You can start with this:
http://www.willbell.com/TM/TelescopesEyepiecesAstrographs.html

Also Roger Ceragioli produced a very comprehensive paper on pretty much all past and present refractor objective design and performance, that paper was available on Internet and I have a printed copy, but he has revised and simplified it many times, its worth your time to find it, Roger is associated with University of Arizona Optics Lab.

Vahe

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orlyandico
Carpal Tunnel

Reged: 08/10/09

Loc: Singapore

Re: history of the apochromat refractor new

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[Re: drollere]
#5471339 - 10/15/12 11:24 AM

http://rohr.aiax.de/chapter%204a.htm

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drollere
Pooh-Bah

Reged: 02/02/10

Loc: sebastopol, california

Re: history of the apochromat refractor new

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[Re: orlyandico]
#5472971 - 10/16/12 10:00 AM

vahe, i have TEA, and although it has a decent history of the 19th century achromat refractor (ch.5) it has nothing specific on the development of the apochromat (ch. 6).

thanks, orlyandico, that is more what i was looking for.

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vahe
professor emeritus

Reged: 08/27/05

Loc: Houston, Texas

Re: history of the apochromat refractor new

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[Re: orlyandico]
#5473028 - 10/16/12 10:33 AM

Quote:

http://rohr.aiax.de/chapter%204a.htm

This in fact is an excerpt from Roger Ceragioli paper that I referred to, click at the link at the bottom and you will see his name appear.

In the earlier version the paper covered a lot more apochromats including a good number of Astro-Physics.

Vahe

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jrbarnett
Eyepiece Hooligan

Reged: 02/28/06

Loc: Petaluma, CA

Re: history of the apochromat refractor *DELETED* *DELETED* new

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[Re: drollere]
#5474963 - 10/17/12 12:11 PM

Post deleted by jrbarnett

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drollere
Pooh-Bah

Reged: 02/02/10

Loc: sebastopol, california

Re: history of the apochromat refractor new

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[Re: jrbarnett]
#5475145 - 10/17/12 01:51 PM

actually, rohr's overview is fascinating. it basically states that the APO is a fully amateur instrument that has never been built. although designed around the turn of the 20th century, it was not manufactured in significant quantities, or at significant apertures, due to material limitations imposed by fluorite or glasses that could substitute for it.

rohr dates the roll out of modern APO's to christen's revival of the design in the late 1980's, which i suppose makes him "the nagler of APOs". this means the APO falls between the SCT and the dobsonian in the evolution of amateur equipment.

i can't find any reference to an APO with aperture much above 7", and price points mean that almost all of the APOs in amateur hands are probably 6" or less. to the OP, one might conclude that there are no APOs being used at large apertures and none used at professional observatories ... unless as guide scopes ...

as for "never been built", rohr also explains why abbe's definition of an apochromat is impossible to meet in practice. thomas back came to the same conclusion.

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Tanveer Gani
scholastic sledgehammer

Reged: 11/02/06

Loc: Washington State

Re: history of the apochromat refractor new

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[Re: drollere]
#5475230 - 10/17/12 02:40 PM

Quote:

actually, rohr's overview is fascinating.

Just a correction: the writeup is not Rohr's. It is by Roger Ceragioli, a well respected optical engineer. Due to some inexplicable reasons, Ceragioli took this writeup offline as well as a great one on how to construct an achromatic refractor lens. Rohr's just made a bootleg copy available.

Tanveer.

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vahe
professor emeritus

Reged: 08/27/05

Loc: Houston, Texas

Re: history of the apochromat refractor new

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[Re: Tanveer Gani]
#5475815 - 10/17/12 08:27 PM

I printed and have saved the very early version of Roger Ceragioli entire paper that was once available on the net, what followed was more simplified subsequent versions until it finally came to an end.

In the early version he lamented about he popularity of current very fast apochromats and insisted that a true apo really should be a F/15 system, the faster versions represent more or less a design compromise, but as best as I can remember this opinion did not appear in later versions.

In fact Roland admitted that all of his faster apos do have inherent 5th order aberrations, it’s the price one pays for speed, but since market demands these one does not hear too much about these issues.

Vahe

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Alan French
Night Owl

Reged: 01/28/05

Loc: Upstate NY

Re: history of the apochromat refractor new

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[Re: vahe]
#5475852 - 10/17/12 08:53 PM

I wish the old 6" f/12 Starfire was still available, or perhaps something a tad larger. But customers voted with their wallets, and the slower instruments are history.

Clear skies, Alan

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Cotts
Just Wondering

Reged: 10/10/05

Loc: Toronto, Ontario

Re: history of the apochromat refractor new

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[Re: drollere]
#5475887 - 10/17/12 09:13 PM

Quote:

i can't find any reference to an APO with aperture much above 7", and price points mean that almost all of the APOs in amateur hands are probably 6" or less.

Bruce, that's probably a bit pessimistic. There must be quite a few TEC 180's out there and Markus Ludes has been selling 8", 9" and larger APO's for a number of years around the planet.

I, too, am wondering if Roland was the first to bring the APO to the amateur community. Unless you find out something unexpected in this thread I suspect we will be able to 'Naglerize" Mr. Christen officially......

Dave

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fred1871
sage

Reged: 03/22/09

Loc: Australia

Re: history of the apochromat refractor new

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[Re: drollere]
#5475947 - 10/17/12 09:52 PM

To add to your reading, Bruce - Dick Suiter's "Star Testing" 2nd edition has some useful discussions of "apochromatic" and what it can be taken to mean.
And Suiter has some thoughts on the first "genuinely-sort-of-real" (my description) apochromatic refractor - the Cooke photovisual, by H Dennis Taylor, in the 1890s.

Suiter's book has a very poor index, so you'll have to read through various relevant sections.

Suiter also discusses various versions of 'apochromatism' and what works best for visual rather than CCD use.

And for extras, Chris Lord has some interesting discussions on his website (Brayebrook Observatory etc).

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jrbarnett
Eyepiece Hooligan

Reged: 02/28/06

Loc: Petaluma, CA

Re: history of the apochromat refractor new

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[Re: Cotts]
#5475993 - 10/17/12 10:22 PM

Yes and there are more than a few TEC 200EDs lurking around, and Tony Hallas' old 206mm A-P, 175mm APM/LZOS triplets also come up on Astro-Mart now and again.

My dream scope is a 12" f/11.8 LZOS/APM OTA (about $160k) on an El Cap mount, under an Ash Dome, off the grid, in a very dark, relatively high, very dry place. Sounds expensive, but not really compared to other hobbies like blue water sailing and exotic cars, and unlike those other hobbies one rarely gets injured in an accident or lost in space while at the eyepiece.

Regards,

Jim

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chboss
professor emeritus

Reged: 03/24/08

Loc: Tokyo Japan

Re: history of the apochromat refractor [Re: jrbarnett]
#5476299 - 10/18/12 03:07 AM

Before "Naglerizing" anybody...

Do not forget Takahashi when discussing who made APO's popular for amateurs in the 1980's. According to the text found here:
http://www.takahashiamerica.com/main_takahashi.htm

The FCT 150 prototype was introduced 1983, using a fluorite triplet design. In Europe the Tak APO's seem to be far greater in number than AP APO's.

best regards
Chris

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Mike Clemens
Frozen to Eyepiece

Reged: 11/26/05

Loc: Alaska, USA

Re: history of the apochromat refractor new

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[Re: chboss]
#5476318 - 10/18/12 03:38 AM

> Yes and there are more than a few TEC 200EDs lurking
> around

24 or 25

I wonder if there are under 300 8" or larger APOs on the planet?

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vahe
professor emeritus

Reged: 08/27/05

Loc: Houston, Texas

Re: history of the apochromat refractor new

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[Re: Cotts]
#5476495 - 10/18/12 07:59 AM

Quote:

I, too, am wondering if Roland was the first to bring the APO to the amateur community. Unless you find out something unexpected in this thread I suspect we will be able to 'Naglerize" Mr. Christen officially......

I believe that Takahashi was the first to introduce very high quality triplet fluorite apos early on to the amateur community with astronomical price tags, the early generation of Astro-Physics were not in the same league in color correction and although AP labeled them apo they were really not color free refractors.

Vahe

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Yu Gu
member

Reged: 06/18/06

Re: history of the apochromat refractor new

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[Re: Mike Clemens]
#5476591 - 10/18/12 09:32 AM

Quote:

> Yes and there are more than a few TEC 200EDs lurking
> around

24 or 25

I wonder if there are under 300 8" or larger APOs on the planet?

My guess would be <150

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greju
Carpal Tunnel

Reged: 10/13/05

Re: history of the apochromat refractor new

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[Re: chboss]
#5476871 - 10/18/12 12:34 PM

Quote:

Before "Naglerizing" anybody...

Do not forget Takahashi when discussing who made APO's popular for amateurs in the 1980's. According to the text found here:
http://www.takahashiamerica.com/main_takahashi.htm

The FCT 150 prototype was introduced 1983, using a fluorite triplet design. In Europe the Tak APO's seem to be far greater in number than AP APO's.

best regards
Chris

Wasn't it the '70s?

http://www.astrosurf.com/re/taka_telescopes.html

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Tanveer Gani
scholastic sledgehammer

Reged: 11/02/06

Loc: Washington State

Re: history of the apochromat refractor new

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[Re: Alan French]
#5476956 - 10/18/12 01:21 PM

Quote:

I wish the old 6" f/12 Starfire was still available, or perhaps something a tad larger. But customers voted with their wallets, and the slower instruments are history.

Clear skies, Alan

I asked Roland exactly this on ap_ug, asking him if he'd consider making the visual-oriented non-ED apos again. (The reason he's not making the big apos is because of ED glass sourcing difficulty). But he chose not to answer, instead answering the other question in my post about Schott. At least he didn't say no.

Tanveer.

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Mark9473
Postmaster

Reged: 07/21/05

Loc: 51°N 4°E

Re: history of the apochromat refractor [Re: jrbarnett]
#5476985 - 10/18/12 01:33 PM

Quote:

My dream scope is a 12" f/11.8 LZOS/APM OTA (about $160k) on an El Cap mount, under an Ash Dome, off the grid, in a very dark, relatively high, very dry place. Sounds expensive, but not really compared to other hobbies like blue water sailing and exotic cars

That's the kind of rationalization you only make if you can afford the price.

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