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Olivier Biot
Amused
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Reged: 04/25/05

Loc: 51°N (Belgium)
The ‘English Fraunhofer’: Resolving a Paradox?
      #4812254 - 09/17/11 07:53 AM

The ‘English Fraunhofer’: Resolving a Paradox?

By Neil English.


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jrbarnett
Eyepiece Hooligan
*****

Reged: 02/28/06

Loc: Petaluma, CA
Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: Olivier Biot]
      #4812583 - 09/17/11 11:27 AM

Bene scriptum est opus.

Nicely done Neil. Great read. Thanks for submitting the piece.

- Jim

Edited by jrbarnett (09/17/11 11:36 AM)


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Jeff Morgan
Postmaster
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Reged: 09/28/03

Loc: Prescott, AZ
Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: Olivier Biot]
      #4812646 - 09/17/11 11:57 AM

A very enjoyable article Neil. They really are timeless scopes.

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hyia
member


Reged: 11/07/10

Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: Olivier Biot]
      #4812792 - 09/17/11 01:27 PM

Thank you for sharing what was obviously the result of a significant amount of research on your part. I've read a number of posts espousing the benefits of longer focal ratio refractors. I'm curious as to where you draw the limit, if any. i.e. It appears that the benefit is linked to the actual focal ratio for whatever reason rather than the lack of false color or ease of figuring. Otherwise, I would think that a high quality doublet of lower focal ratio would be just as good.

So, assuming "good" optical quality, it seems there is a performance benefit of a 4" f11 over a 4" f9. (Assume we are talking about planetary or double star performance.) Would then a 4" f15 of similar quality be even better, and a 4" f20 better still?

I realize this question is not well defined and appreciate any answer you can give. Also, do you have any recommendations for commercially available 4" refractors? Thank you.


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7331Peg
Sirius Observer
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Reged: 09/01/08

Loc: North coast of Oregon
Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: Olivier Biot]
      #4812853 - 09/17/11 02:07 PM

A great piece of work, Neil. It took well over an hour to read through it because I kept getting stuck on the photos of those beautiful Cooke refractors. Stupendous works of optical and visual art.



John


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ukcanuck
Vendor (Skylight Telescopes)
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Reged: 11/07/06

Loc: London, UK
Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: 7331Peg]
      #4812922 - 09/17/11 02:47 PM

The Fry Telescope at Mill Hill (I just can't bring myself to say the Fry Cooke ), is one of the most impressive telescopes I've ever seen. There's some information on the restoration here.

It's always surprised me how little information there is online about T. Cooke and Sons. Thanks for your effort Neil, this is a great read.


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David Castillo
Carpal Tunnel
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Reged: 09/09/06

Loc: Carmel Valley, Ca
Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: ukcanuck]
      #4813123 - 09/17/11 05:08 PM

A gem of an article, Neil. I am awed by these instrument's incredible focal lengths. As you point out, by today's diminishing observing conditions, our needs in a telescope have evolved, but history has proven the quest for superior optics has never faltered. Scopes that sport double digit focal lengths, although often criticized as anachronisms, cannot truly be appreciated until one has the good fortune to be able to look through one. Thank you for the great read.
---
Dave


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Adam Taylor
insignificant bystander
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Reged: 11/11/10

Loc: Arizona
Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: Olivier Biot]
      #4813226 - 09/17/11 06:20 PM

Wonderfully written.

Some people dream of having an Italian supermodel for a wife. Others, a fancy sports car parked in their driveway. I dream of a permanently-mounted long-focus achromat.


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Astrojensen
Post Laureate
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Reged: 10/05/08

Loc: Bornholm, Denmark
Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: Adam Taylor]
      #4814046 - 09/18/11 04:37 AM

Quote:

Some people dream of having an Italian supermodel for a wife. Others, a fancy sports car parked in their driveway.




Forget about these. Too expensive in initial purchase, maintenance and running costs.

Quote:

I dream of a permanently-mounted long-focus achromat.




Now you're talking!


Clear skies!
Thomas, Denmark


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Lightning
sage


Reged: 07/04/10

Loc: Canberra, Australia
Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: Astrojensen]
      #4814109 - 09/18/11 06:43 AM

Thank you Neil for such a wonderfully researched and beautifully written article!

I first used the 9" Cooke (F/15 triplet) at Carter Observatory in Wellington, New Zealand when I was 7 years old on a public night and got to see Alpha Centauri and Alpha Crucis. When I was 14 I was very fortunate to be taken on as evening assistant running the telescopes at the observatory and got to enjoy many more sights through both this scope and the 6" F/18 that had been the main telescope of the late Peter Read. Both are amazing instruments, the colour correction of the Cooke triplet providing very true views of double stars.

Sadly the glass in the 9" deteriorated rapidly in the late '90s and was replaced with a larger 9-3/4" achromatic objective crafted by Gary Nankivell (sadly now also departed). At the same time it was expertly restored by Gordon Hudson and Stewart Mawson to the same black & brass as the Fry telescope.

So much history is attached to this scope and those like it.

Thank you so much again for bringing back so many happy memories with the Cooke's I've got spend time with.

Best wishes,
Cameron Jack


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buddyjesus
Carpal Tunnel
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Reged: 07/07/10

Loc: Davison, Michigan
Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: Lightning]
      #4814551 - 09/18/11 01:05 PM

Fantastic article

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astroneil
Pooh-Bah
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Reged: 07/28/09

Loc: res publica caledoniae
Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: buddyjesus]
      #4815991 - 09/19/11 10:27 AM

Thank you all very much for your kind words.

Kind Regards,

Neil.


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jrbarnett
Eyepiece Hooligan
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Reged: 02/28/06

Loc: Petaluma, CA
Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: Olivier Biot]
      #4816009 - 09/19/11 10:36 AM

So, would that make Faunhofer the "Bavarian Cooke"?

- Jim


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KennyJ
The British Flash
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Reged: 04/27/03

Loc: Lancashire UK
Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: jrbarnett]
      #4816260 - 09/19/11 01:25 PM

A truly wonderful , brilliant piece of work , as thoroughly researched , well - written , superbly illustrated and enjoyable to read as I could possibly hope any published book on the subject could be .

And all for FREE !

Thank you , Neil !

Kenny


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Mr Onions
Two Time International Photographical Competition Winner
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Reged: 04/14/07

Loc: Newcastle upon Tyne.
Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: KennyJ]
      #4816544 - 09/19/11 04:09 PM

You see that white spot on Saturn by the famous comedian/actor Will Hay.
He was funny.


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rookie
Good Night Nurse
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Reged: 01/14/06

Loc: St. Petersburg, FL
Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: Mr Onions]
      #4816881 - 09/19/11 07:17 PM

I really enjoyed reading your article, Neil. It's a great history lesson for us to appreciate those that built the foundations of knowledge for our modern telescopes.

The Fry telescope is such a beautiful restoration. If I ever get to London, I'd love to go and see it.


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astroneil
Pooh-Bah
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Reged: 07/28/09

Loc: res publica caledoniae
Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: rookie]
      #4819732 - 09/21/11 09:46 AM

Thanks Kenny & Rookie,

My up-and-coming book will also feature a piece on the restoration of Sir Patrick Moore's 5" f/12 Cooke refractor by Steve Collingwood at Telescope House, which is housed in Sir Patrick's observatory at Selsey, on the West Sussex coast.

Some basic info here:

http://www.telescopehouse.com/acatalog/Patrick_Moore_Cooke_Telescope_Restoration.html

Steve was kind enough to provide some amazing insights into the quality of this instrument - both mechanical and optical.

Kind Regards,

Neil.

Edited by astroneil (09/21/11 09:47 AM)


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ukcanuck
Vendor (Skylight Telescopes)
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Reged: 11/07/06

Loc: London, UK
Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: rookie]
      #4820105 - 09/21/11 01:22 PM Attachment (292 downloads)

Quote:

The Fry telescope is such a beautiful restoration. If I ever get to London, I'd love to go and see it.




UCL/Mill Hill did a beautiful job on this refractor. An interesting bit of trivia on this is that the focuser had been polished so many time, the T Cooke and Sons engraving had almost been polished away.

To keep it disappearing forever, the restoration team encased the focuser in plexiglass. This keep the brass from tarnishing and it looks great. It also creates something of a 'museum piece' feel about the focuser.

A (not very good) picture here:


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ukcanuck
Vendor (Skylight Telescopes)
*****

Reged: 11/07/06

Loc: London, UK
Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: ukcanuck]
      #4822003 - 09/22/11 01:44 PM Attachment (293 downloads)

A recent trip to the South of France brought me to a little town called Puimichel, where I met a gentleman named Jean Baptiste who owns owns a 9" T. Cooke and Sons objective.

He found the refractor in a terrible state some years ago in a forgotten back garden exposed to the elements. Its' origins date to around 1930, when the objective travelled from York, was housed in a majestic ota built by the French company Manent, and was originally placed in a stately home just a few miles from where it currently resides.

When JiBe found it, it was in a terrible state (birds were living in the ota!)

Some background (and lots of pictures) can be found here. This is a Google translation, so the French (and English) will be a little awkward.

My first foray in Youtube is a short video of this scope in it's roll-off observatory: La lunette du père JOSSET

Edited by ukcanuck (09/23/11 04:06 AM)


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7331Peg
Sirius Observer
*****

Reged: 09/01/08

Loc: North coast of Oregon
Re: The ‘English Fraunhofer’: Resolving a Paradox? new [Re: ukcanuck]
      #4822986 - 09/23/11 12:55 AM

Amazing, amazing, amazing. It'll take a week to dry my desk off after looking at that. Normally red wouldn't be my first choice for a scope, but I'll gladly make an exception in this case!

Did you get a chance to look through it, Richard?


John


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