Re: ATM which one first

[Gary Seronik <gseronik@direct.ca>]

At 09:48 PM 6/11/1998 -0400, David McCarter wrote:
>
>>1. I have looked at different kinds of focuser, Ilike the helical the
>>best. Rack and pinion are fine but just doesn't appeal to me. Is there
>>any draw backs of this type? Is there a general "best"?
>
>The helical takes forever to change focus if your eyepieces are not
>strictly parfocal. I thought I would like them too, but discovered I had
>not enough patience.

Hi Dave:

You know, I hear this a lot as a knock against helical focusers and
frankly, I just don't get it.  I mean, am I the only one with reasonably
parfocal eyepieces?  Seriously, I've got quite a mixed bag, and I think the
biggest difference between eyepieces is about 1/4" of focus travel.  This
is pretty easy to deal with, you just slide the eyepiece in until it's
close to focus and use the helical for fine-tuning.

On the other hand, one of the big advantages helicals have is the precision
with which focus can be achieved.  For f/6 and under they're a must.  At
f/4.5, accurate focus with a r&p is almost a matter of luck.

One helical of guy's opinion...

Gary Seronik