Crayford Focusers for Meade SCT?

I'm sick and tired and I'm not going to take it anymore. Backlash.
Stars jumping around while I focus -- especially in the tiny field of
my ST-4.

Thus, I'm looking for recommendations for a Crayford focuser for my 8"
Meade tube. It could be motorized --or not.

How does one use such a focuser; i.e., do they have sufficient travel
to act alone once the primary mirror has been locked in a certian
position, or does one have to use the coarse focuser to get in the
ballpark and then lock the mirror and go to the Crayford (as one does
with Meade's electric focuser?)

Feathertouch? JMI? ???

TIA

Davoud

--
usenet *at* davidillig dawt com

"Davoud" wrote in message
...
I'm sick and tired and I'm not going to take it anymore. Backlash.
Stars jumping around while I focus -- especially in the tiny field of
my ST-4.

Thus, I'm looking for recommendations for a Crayford focuser for my 8"
Meade tube. It could be motorized --or not.

How does one use such a focuser; i.e., do they have sufficient travel
to act alone once the primary mirror has been locked in a certian
position, or does one have to use the coarse focuser to get in the
ballpark and then lock the mirror and go to the Crayford (as one does
with Meade's electric focuser?)

Feathertouch? JMI? ???

TIA



RACK AND PINION IS THE WAY FOR THE LONG TERM. CRAYFORDS WEAR OUT. -END-

Davoud wrote:
I'm sick and tired and I'm not going to take it anymore. Backlash.
Stars jumping around while I focus -- especially in the tiny field of
my ST-4.

Thus, I'm looking for recommendations for a Crayford focuser for my 8"
Meade tube. It could be motorized --or not.

How does one use such a focuser; i.e., do they have sufficient travel
to act alone once the primary mirror has been locked in a certian
position, or does one have to use the coarse focuser to get in the
ballpark and then lock the mirror and go to the Crayford (as one does
with Meade's electric focuser?)

Hi:

Yes. Unless your eyepieces are nearly parfocal or you leave the camera
in place all the time, you're still going to be using the main focuser.
The Crayford will not provide enough range for large focus changes.

Also, beware of focus problems. If you have things like reducers and 2
inch diagonals in your optical train, moving everything back another
inch or two with the focuser may mean you can no longer reach focus.

Both the units you mention are very nice. I've used the William Optics
Crayford and like it.


Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
Like SCTs and MCTs?
Join the SCT User Mailing List.
http://www.groups.yahoo.com/group/sct-user
============================
See my home page at
http://skywatch.brainiac.com/astroland/index.htm
for further details!
============================
For Uncle Rod's Astro Blog See:
http://journals.aol.com/rmollise/UncleRodsAstroBlog/


Yes.

EP Guy wrote:
RACK AND PINION IS THE WAY FOR THE LONG TERM. CRAYFORDS WEAR OUT. -END-

Hi:

Who sells a rack and pinion focuser designed to screw onto an SCT rear
port? And I have never, ever had a problem with a Crayford wearing out.
At least, anyway, the one on the 12.5", a JMI, is about 8 years old and
has not worn out yet despite a good bit of use. ;-)

Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
Like SCTs and MCTs?
Join the SCT User Mailing List.
http://www.groups.yahoo.com/group/sct-user
============================
See my home page at
http://skywatch.brainiac.com/astroland/index.htm
for further details!
============================
For Uncle Rod's Astro Blog See:
http://journals.aol.com/rmollise/UncleRodsAstroBlog/

I'm sick and tired and I'm not going to take it anymore. Backlash.
Stars jumping around while I focus -- especially in the tiny field of
my ST-4.

You might want to look at the Borg non-rotatiing helical 1.25" focuser
(#7315) with the 1.25" drawtube adapter (#7316). I think this combo goes
for less than $100. This unit is very nice for fine focusing (.5" travel),
and might allow you to live with the built-in focuser for coarse focusing
only.

Dennis

Hi all

Here is a shot from last night of the Moon
Rupes Recta in particular.



http://home.comcast.net/~sctuser/wsb...D-2646553.html




It was the only one of three avi's I could get
to work. The wind got so bad, the other two, were
just non stop vibratory images.
As it was it was 32F....

All current lunar pic's are correct image oriented

I am gettin better






--
AM

http://sctuser.home.comcast.net

CentOS 4.2 KDE 3.3

Davoud wrote:
I'm sick and tired and I'm not going to take it anymore. Backlash.
Stars jumping around while I focus -- especially in the tiny field of
my ST-4.

I was wondering when you would run across this


Thus, I'm looking for recommendations for a Crayford focuser for my 8"
Meade tube. It could be motorized --or not.

JMI - I have them on all my Newts. They work well. Go for the dual speed
version. Or if money isn't much of a problem go with the Van Slyke.

You'll get so tired of focusing manually that Robo-focus and Focus Max
is inevitable. Don't fight it.


How does one use such a focuser;

Place the add on focuser at mid travel and focus the SCT using its focuser.

i.e., do they have sufficient travel
to act alone once the primary mirror has been locked in a certian
position, or does one have to use the coarse focuser to get in the
ballpark and then lock the mirror and go to the Crayford (as one does
with Meade's electric focuser?)

I have no experience with a C-8. But with a C-11 There is too much
temperature shift between Summer and winter to handle a single primary
focus position. So I use two different positions of the primary based
upon the time of year (temperature).

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 ?

Oh yes one other point..... always focus uphill. AKA mirror moving up.
focus shift is minimal when done that way.


Bill

--

William R. Mattil : http://www.celestial-images.com

Davoud wrote:
Thus, I'm looking for recommendations for a Crayford focuser
for my 8" Meade tube. It could be motorized --or not.

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/