Re: ATM Help: New TV BinoVue too heavy for my Crayford focuser

[David McCarter <mccarterd@claven.fanshawec.on.ca>]

>I've got a 7" Sonotube dob with a Crayford 1.25" focuser.  Just got a 2nd
>hand Televue BinoVue and now discovered that the combination of the Binovue
>along with two TV Plossl's or TV Radians is just too much for the little
>Crayford to handle.

The Crayford is just not designed to take a load. The draw tube is held by
ball bearings and a single friction rod, and it just slides with very
little force. The nice thing is it is smooth to focus, and low profile. I
wonder how often a Type 5 Nagler slips in a Crawford?

If you need a focuser that is both low profile AND will hold a ton of
weight, you need to go to a Helical Focuser. Not one of those crappy,
sloppy, hard to turn plastic ones you have probably seen. Have a look at
DAR Astro's 1.25 inch dual thread aluminum and bronze helicals. It has a
four start 5tpi for quick focus change and a 20tpi for smooth fine focus.
Nicest one out there.
Here's the URL:http://www.execulink.com/~sanjo/
or try:http://www.oneilphoto.on.ca

I know these guys really well, but I'm not in business with them.

Dave