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Old 19-02-2021, 12:30 PM
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LewisM
Novichok test rabbit

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Dump dog

Picked this one up at the local dump recycling centre recently. Only thing missing were the eyepieces, but I obtained some Vixen 0.965" EP's.

I'd say this lived in someone's study here in Canberra for decades. I recall very clearly being fascinated by the Short Tube Catadioptric 13T listed in Tasco's catalogues for years, always wanting one. I like many thought these are Bird-Jones, but was kindly informed by Alex these are Barlowed Newts, which this definitely is after diassembling to clean the optical window.

Field curvature is obvious, but not evil being barlowed to f/8 and change. Being Japanese, it is well made and sharp optically.

Can't complain considering it is in superb condition, came with its original EQ mount and cost $20 because everyone at the tip shop thought it was broken (no EP's = no image ). I'll use it visually for a while, but yes, it may well end up on the classifieds here eventually, though not for $20...the EP's cost me more
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  #2  
Old 19-02-2021, 12:57 PM
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mental4astro (Alexander)
kids+wife+scopes=happyman

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Ditto with drooling over one of these as a kid too, Lewis

It's in GREAT condition for being a Dump Dog! Great find!

When I went with my parents to Hobbyco many moons ago (1983) to get my first ever scope, the price tag on the 13T was eyewatering and crushing to a kid's dreams.

For a barlowed Newt, you can do much worse than the 13T . It has a respectably manufactured spherical mirror, which unless it actually is well figured, you are in for a world of pain with a faecal-ty one.

If you are after a TRUE Bird-Jones or Jones-Bird (take your pick on the order), the Tasco 8V is the one you are after. The clue being that it came with the Vixen Polaris mount, not the dicky EQ1 the 13T comes with.

Celestron also made a Bird-Jones Newt for a very brief time. Then mass production techniques were able to quickly punch out quality fast parabolic mirrors, and the Celestron Bird-Jones died a quick and quiet death.

FWIW, the Bird-Jones has a purpose made corrector lens that sits between the secondary mirror and the spherical primary. The corrector was designed to correct for spherical aberration. THIS is what made the true Bird-Jones, and hence the 8V, expensive - all the optical components were quality items. The pic below shows the optical window of an 8V removed from the OTA showing the corrector lens assembly below the secondary.

If the Newt you have has a lens shoved down the focuser draw tube, this is a barlowed Newt, NOT a Bird-Jones. The lens is a cheap barlow, NOT a corrector lens of any description. It is purely ignorance that has people confuse the barlowed Newt with a Bird-Jones. The Bird-Jones is a specific telescope design, just like an SCT or Classical Cassegrain or Maksutov Newtonian. No one confuses these with any other scope design. The Bird-Jones is exactly the same.

One clue to the true nature of barlowed Newts is they are ALL cheap and on cheap and nasty wobbletron EQ1 mounts, they DO NOT correct for spherical aberration, plus whatever other image distortions there are from a poorly figured cheap-arsed spherical mirror. The Bird-Jones design was always an expensive way to overcome spherical aberration.

Alex.
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Last edited by mental4astro; 19-02-2021 at 01:11 PM.
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Old 19-02-2021, 01:14 PM
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leon
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Wow nice find indeed, all that for 20 bucks, you did well.

Leon
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