Crayford focusers?

[Kaptain K]

OK, I'm going to expose my ignorance here. I know that crayfords are good, but what exactly are they? What makes them so good?

[aurora]

They use friction alone, rather than a rack and pinon like most other focusers.

So the good ones move smoothly, with no slop or jerkiness. Good ones also have multiple speeds, with a fast and a slow control.

I absolutely love the one I put on my home built Dob.

[Dave Mitsky]

The Starlight Instruments dual speed Feather Touch is one of the best focusers available.

http://www.starlightinstruments.com/

MoonLite makes some very fine Crayford focusers that aren't quite as expensive.

http://www.focuser.com/storefront.php

Dave Mitsky

[Kaptain K]

Very nice Dave...but I'm not looking to buy one right now. I was just curious as to how they work!

[RickJ]

See this link for the design info.
http://www.astronomics.com/main/category.asp/catalog_name/Astronomics/category_name/GPPM30TX16PT8MEGHTP24W1JD4/Page/1

Rick

[Wakenaam]

try this if you need more detail and are thinking diy.....
http://www.atmsite.org/contrib/Sapp/Focuser/CrayFocus.htm

[torque of the town]

Highly recommended I have one on my WO scope with a 10:1 ratio on the fine focus.