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John wall 30" refractor.

Discussion in 'Telescopes and Mounts' started by kevan hubbard, Jun 24, 2018.

John wall 30" refractor.

Started by kevan hubbard on Jun 24, 2018 at 1:13 PM

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  1. kevan hubbard

    kevan hubbard Well-Known Member

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    kevan hubbard, Jun 24, 2018
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    I've come across a strange telescope on the Internet indeed the worlds 5th biggest refractor.the Yerkes 40" is of course the biggest. The John wall is reported to be the biggest refractor built since 1914!104 year ago!and the largest built by a single person, John wall at a guess?it's owned by an amateur astronomy group based in hanbury, Oxfordshire, England. Hanbury is a village near Banbury and is roughly halfway between Birmingham and London. There's very little information on it,I wonder how John wall acquired such a huge lense?it must weigh a ton.the telescope looks to have an open tube a bit like some big reflectors.I'm guessing it uses 2" eye pieces.love to have a look through it. I think that the next biggest refractor in England, probably Europe, would be the 28" one in Greenwich, London, which I've seen but not looked through, sadly!,although they did have a very nice picture of Saturn on a TV monitor. Big drop down in aperture to my next biggest refractor, the 13" Grubb, in Wellington, New Zealand.
     
  2. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jun 24, 2018
    #2
  3. kevan hubbard

    kevan hubbard Well-Known Member

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    kevan hubbard, Jun 24, 2018
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    Yes I looked him up later.born in crayford lived latterly in Coventry not too far from hanbury.Coventry would have very undark skies being a fairly large city itself and the greater Birmingham conurbation is just away to its north west.wonder if any refractor telescopes have ever been used in space, all the ones I can think of are reflectors.
     
  4. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jun 24, 2018
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    It depends where he lived in Coventry. Wolverhampton is a city, yet there are areas of Wolverhampton surrounded by pig farms and woodland with fairly dark skies.
     
  5. kevan hubbard

    kevan hubbard Well-Known Member

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    kevan hubbard, Jun 24, 2018
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    He probably lived in an affluent suburb assuming that the Crawford focusing mechanism made him a large sum of money! Based on my bortle map Coventry looks yellow at best,can't remember that limiting magnitude, I think about 5?whilst hanbury is green around about 6.pig farms might be well avoided to stargaze from!
     
  6. Dave In Vermont

    Dave In Vermont Well-Known Member

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    Dave In Vermont, Jun 24, 2018
    #6
    Years ago I read that NASA was considering sending aloft an SCT - either a Celestron or Meade - then it dropped-off the RADAR and I never heard mention of this again. I do wonder about it from time-to-time,
     
  7. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jun 25, 2018
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    Wall never patented the Crayford and didn't make a penny from it. The point I tried to make about the farmland is that some large developed areas can be interspersed with greenbelt. Particularly in the English Midlands, where I was born.
     
  8. kevan hubbard

    kevan hubbard Well-Known Member

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    kevan hubbard, Jun 25, 2018
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    So he was a bit like Dobson who also never patented his dobsonian mount.Coventry has a little bit of countryside between it and Birmingham to it's north west,then it seems to be a solid wall up urban sprawl from Birmingham to Wolverhampton there is however, I note,a dark skies discovery site in Walsall, pex hill.might be OK for looking north but most of the interesting southern stuff Sagittarius, Scorpius, etc,would be within Birmingham's light dome.the north is less interesting as it's easier to see but that should be fairly clear as there's nothing major due north until Stoke on Trent.
     
  9. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jun 25, 2018
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    English cities weren't really planned, unlike US cities, and are normally not built on a grid system. Most cities grew organically over a period of millennia and often don't have large centres, which means they can sprawl somewhat. I don't know where Wall lived exactly, but it doesn't necessarily mean that he didn't have relatively dark skies. Having said that, Coventry was rebuilt somewhat after being vaporised in WWII. I have relatives who lived over 50 km from Coventry as children, but they still felt the bombs dropping on the city as they sat in an Anderson shelter.
     
  10. kevan hubbard

    kevan hubbard Well-Known Member

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    kevan hubbard, Jun 25, 2018
    #10
    Yes I've been to Birmingham, a very big city but the central core of the city is tiny.reminded me of a north American city,with sky scrapers in the middle which you can see for miles off coming in by rail.in fact I recall seeing Venus from Birmingham. I suppose, like Coventry, it was bombed during ww2 as gun making was a popular activity there?
     
  11. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jun 25, 2018
    #11
    Birmingham is a fairly modern city, probably only around 200 years old. I don't know about gun making being popular, but thousands of Supermarine Spitfires amongst other aircraft, tanks and military vehicles were manufactured there. The industrial Midlands, the North, South Wales and large areas of Scotland and Northern Ireland were all heavily saturation bombed in WWII as they were centres of industry.

    Oh yeah, Coventry wasn't an industrial centre, it was chosen as one of the Baedeker raids.
     
    Last edited: Jun 25, 2018
  12. Gabby76

    Gabby76 Well-Known Member

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    Gabby76, Jun 25, 2018
    #12
    John Dobson never invented the mount that is named after him, the style was around for many years but he made it very popular through his constant outreach.

    I just saw a image of the 30" refractor... That is one ugly telescope!
     
  13. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jun 25, 2018
    #13
    I always suspected this lol.
     
  14. Gabby76

    Gabby76 Well-Known Member

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    Gabby76, Jun 25, 2018
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    He probably could have patented it after his modifications to the original design.
     
  15. kevan hubbard

    kevan hubbard Well-Known Member

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    kevan hubbard, Jun 25, 2018
    #15
    Birmingham small arms and Webley where based in Birmingham. BSA also made motor bikes plus pedal bikes. Webley made service revolvers for officers they also developed a very strange, like something out of aliens ,automatic pistol,the Webley Mars, which I think was more powerful than a .44 magnum which hadn't been invented at the time of the Webley Mars. Yes the John wall is ugly and short,must have a short, fast, focal length so I'm guessing mainly used for deep sky rather than planets and the moon?
     
  16. Gabby76

    Gabby76 Well-Known Member

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    Gabby76, Jun 25, 2018
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    The refractor is f/12 so not that fast or wide.
    I would assume it was used with a camera of some type instead of a diagonal/ eyepiece combination as if it could use a 2" diagonal the maximum FOV would be 0.3° TFOV
    Some more information about it would be interesting.
    The Zerochromatic is a offshoot of the Dialyte and is a nicer looking/ more portable package
     
  17. kevan hubbard

    kevan hubbard Well-Known Member

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    kevan hubbard, Jun 25, 2018
    #17
    The 30" lense would be very heavy and hard to get.I wonder where this John wall got it from?whilst people grind their own mirrors for large reflectors I've never heard about anyone making their own lenses for very large refractors.they must have made little ones in days gone by for small refractors but a 30" one is quite a different matter.if it's home made I'm going to guess the 30" lense is uncoated.
     
  18. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jun 25, 2018
    #18
    I don't know. I know John Dollond didn't actually originally design the achromatic doublet, but he held the patent. Dollond & Aitchison was a well known British high street opticians brand until Boots bought them out.
     
  19. Mak the Night

    Mak the Night Well-Known Member

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    Mak the Night, Jun 25, 2018
    #19
    Screenshot 2018-06-25 at 16.47.53.png
     
  20. Gabby76

    Gabby76 Well-Known Member

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    Gabby76, Jun 25, 2018
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    Cool! Where did you find the image of me clearing out reflector users??
     
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