I have found an interesting article on the origins of the Crayford Telscope Focuser, which can now be accessed here:

www.model-engineer.co.uk/news/article/the-crayford-telescope-focuser/23813

I hope non-astronomical folk won't object too loudly. Please enjoy!

Neil

Edit [prompted by Jason]

Neil ... Thank You, Thank You so much !!

Unfortunately, it appears that I am not worthy to read the article.

MichaelG.

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[quote]

Error

The article cannot be found.

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Meanwhile; this may be of interest

http://www.crayfordmanorastro.com

Edited By Michael Gilligan on 22/07/2016 20:38:20

Working OK for me, perhaps you need to thank Neil first

Publish check box now ticked

Neil

Thank you [sincerely this time]

MichaelG.

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Well, it would be ... You are a Moderator with added priviledges.

MichaelG.

I don't think I can even get it unless Neil remembers to tick the right box, assume he did it between your post and mine.

I get a subscribers only msg.

However I am well aware of the original design. As is this

**LINK**

A lot were also made using ball races for the "bearings". I'm not entirely sure it was just down to Crayford either but that would be hard to prove now.

John

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Should be visible to all now.

Looks like I checked the 'subcribers only' box instead of the 'publish' one when I first put it up.

Neil

I know John Wall, he has never claimed to have designed the 'Crayford' focuser from scratch but developed from existing ideas which he combined. Although others have tried to patent his ideas he never did.

Not a novel idea even in 1970. I had optical lab equipment, both commercial and locally made, using the same principle to move microscope tubes and the like dating back to 1950's at least. One, a modified travelling microscope, had a plain brass tube rather than chromed so probably rather older. Great thing in such applications is it gives you fast rough focusing by simply sliding the tube in and out.

As I recall matters, bearing in mind its 10 years or so since I last saw any of it, the common commercial version used two cones each side of a plain centre portion releived so as to clear tube to provide the drive with a similar twin cone arrangement underneath. A simple leaf spring pushing down on the plain centre portion provided drive pressure. Also seen it used on engineers microscopes.

Clive.

Edited By Clive Foster on 23/07/2016 15:13:53

I have a vague recollect I saw a very similar arrangement in an old astro book. If I remember correctly it also showed a cassegrain with 2ndry mirror movement for focusing. Seen when I was at school so can't be sure.

John

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one for the star watchers

just watched an item on the local BBC1 NW news about the Manx dark sky

see :---

http://www.bbc.co.uk/news/world-europe-isle-of-man-20005229

more about the Manx dark sky on inside out BBC 1 NW at 19:30 tonight

http://www.bbc.co.uk/programmes/b0071mrm

John

Edited By john swift 1 on 13/02/2017 19:16:20

That would be one of the Six Kingdoms you can see from the top of Snaefell.

Geoff

Yes , I have walked up to the top of snaefell a few times !

John

Luck Mark Noel

I heard today that John Wall has passed on.

Ironically the drawtube I am working on at the moment is for a Crayford Focuser.

Neil

John Wall also built a 30" refracting telescope. This may not sound particularly unusual, but it is the largest refracting telescope ever built by an individual and the equal fifth-largest refractor ever built!

www.hanwellobservatory.org.uk/telescopes/john-wall

Neil

Actually, Geoff, we always say it is seven kingdoms:
England, Ireland, Scotland, Wales,
Heaven,
Neptune's, and
Mann itself

Edited By Dave Martin on 29/01/2018 21:55:32