Crayford Focusers: Thanks!

John Steinberg:
A cheap but often effective fix:
http://www.petersonengineering.com/S..._focus_kit.htm

Ordered, thank you. I have been through the prescribed
take-out-the-slack regime twice with limited effect.

Dennis Woos:
You might want to look at the Borg non-rotatiing helical 1.25" focuser...

Looking and considering, thank you.

William R. Mattil:
JMI - I have them on all my Newts...

Also under consideration.

I'll confess to being confused because I was under the impression that
you had a flip mate for the ST-4 ? If that's the case it's a trvial
matter to recenter the guidestar isn't it ?

It has been said that, not only am I confused, but I am a carrier of
confusion. I'm sorry. Yes, but I removed the flip mate for some reason
that I can't remember offhand -- but I often use a solid-state voice
recorder in the zerbat'ry to help me remember critical little things,
and I'll look that up with a view toward fixing whatever I thought was
wrong. You, on the other hand, would not need such a thing. Following
your sage writings on various forums, it is apparent that you have a
prodigious memory.*

:
Though I have Crayfords (JMI and Meade on mine), I would never
do it again. The absolute best focuser is the Clement; see:
http://www.clementfocuser.com/

Holy s**t! Is that contraption OSHA approved? It looks like a threat to
life and limb! But I've tracked down a couple of users, and they say it
is awesome.

Thanks to all.

Davoud

*True story from a small division where everyone knew everyone else;
names changed slightly: "Floyd, my fitness reports say I'm doing a
great job. It's been that way for years, yet I have nearly 10 years in
grade. When am I going to get promoted!?"
"It's a coincidence that you should ask that now. I've just been
reviewing the list for the current cycle and you are at or near the top
of the list. Err, uh, what did you say your name was again?"

--
usenet *at* davidillig dawt com

Davoud wrote:


Holy s**t! Is that contraption OSHA approved? It looks like a threat to
life and limb! But I've tracked down a couple of users, and they say it
is awesome.

Guy in our club has one. It is a massive extremely
well made, and nicely machined piece of gear. The
smoothness of operation has to be felt, to be appericated
it is that good. This is on a 16" plus dob.



--
AM

http://sctuser.home.comcast.net

CentOS 4.2 KDE 3.3

John Steinberg wrote:
Come to think of it, other hobbies too have their own menu of rituals,
folklore and home brew remedies.

Anyone recall the trick with audio CDs?

As I recall it, the Golden Ear ******s would have you believe that
running
a green felt tip pen around the edge of a CD improves the sound. These
same clowns claim one needs to "break in" speaker wire. Yeah, sure.
:-)

Davoud wrote:
I have been through the prescribed take-out-the-slack regime
twice with limited effect.

John Steinberg replied:
I'm almost convinced someone started that "fix" as a joke. But you
know, in amateur astronomy, it's been my experience that the power of
suggestion and the related placebo effect is very prevalent.

I didn't see it that way at all -- are you talking about this
procedure, which comes from Meade
http://www.mapug-astronomy.net/AstroDesigns/MAPUG/FocusBkL.htm? It
seems to make sense, even if they did call the focusing knob "the
shiney aluminum focus knob," and it did remove /some/ of the backlash
from the focuser.

...

Anyway, keep us posted on what works and what doesn't. We all hate
backlash. Well, those of us who suffer from it.

I'll certainly do that, starting as soon as I install the Peterson
Engineering kit.

Did you have a look at the Clement focuser
http://www.clementfocuser.com? It looks like it ought to be on the
cover of /Analog/ .

Davoud

--
usenet *at* davidillig dawt com

John Steinberg wrote:
Davoud wrote:


I didn't see it that way at all -- are you talking about this
procedure, which comes from Meade
http://www.mapug-astronomy.net/AstroDesigns/MAPUG/FocusBkL.htm? It
seems to make sense, even if they did call the focusing knob "the
shiney aluminum focus knob," and it did remove /some/ of the backlash
from the focuser.


Perhaps the most elaborate description of the procedure ("shiney"
notwithstanding), but that's essentially the one.

Having done this on a number of SCTs (and MAKs), I have never noted any
substantive change in focus backlash but I'm just a single data point.
If it's worked for you and others, I sit corrected.



Did you have a look at the Clement focuser
http://www.clementfocuser.com? It looks like it ought to be on the
cover of /Analog/ .


Hehe. I recall Don posting here *several* years ago with tantalizing
tidbits about his new revolutionary focuser but never responding to
follow-up questions. Must admit that's the first time I've seen it.
The only thought that comes to mind is res ipsa loquitur.


Looks like it would be a problem with viewing anything overhead, as the
structure is likely to smack into the support.

On Sat, 11 Feb 2006 09:19:21 -0500, John Steinberg
wrote:

Having done this on a number of SCTs (and MAKs), I have never noted any
substantive change in focus backlash...

Agreed. The procedure can, however, dramatically reduce both focus image
shift and mirror flop. Most backlash can be eliminated by replacing the
plastic thrust bearings in the focuser assembly with roller thrust
bearings.


Hehe. I recall Don posting here *several* years ago with tantalizing
tidbits about his new revolutionary focuser but never responding to
follow-up questions. Must admit that's the first time I've seen it.
The only thought that comes to mind is res ipsa loquitur.

The engineering quality of the focuser is admirable, but the design is
far from "revolutionary". I was using a similar focuser years before
Clement "invented" it, and in the late 70's we used lab jacks to
position instruments at Big Bear Solar Observatory. Clement's patent
would fall fast to prior art claims if it were ever challenged.

I would not normally recommend using an external focuser on an SCT (at
least not for imagers), but if I did the Clement focuser would be high
on my list because of its low profile.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Chris L Peterson wrote:
The engineering quality of the focuser is admirable, but the design is
far from "revolutionary". I was using a similar focuser years before
Clement "invented" it, and in the late 70's we used lab jacks to
position instruments at Big Bear Solar Observatory. Clement's patent
would fall fast to prior art claims if it were ever challenged.

"Somewhere" in one of the Yahoo groups, a thread mentioned that some
early Celestron SCT had something similar to both hold and move the
primary mirror cell for focusing. In other words, the "jackscrew" was
internal and the primary never succumbed to mirror flop/flip/slop.

Apparently that mechanism was abandoned in a cost-cutting move
soon afterwards; 'tis a shame.