Re: [APML] needed- an excellent sense of direction

["Mike & Dianna" <galaxy@ncweb.com>]

Hey Bobby,

Dont have an answer to which way to adjust your focuser, but, what I do for
squaring my focusers to the opposite side of the tube is replace the
secondary mirror with a lenght of 3/8 threated rod with a hole drilled in it
and placed where the center of the secondary is. I then turn on the laser
then adust the focuser till the laser goes through the hole and hits the
backside of the tube. This seems to work well for me even with offset
secondarys.
Mabey this is how your already doing it, i dont know for sure.
Just my 2 cents and hope it helps ........

Mike Leitch
galaxy@ncweb.com
Astrophotography website
http://www.ncweb.com/~galaxy/home/astropho.htm

----- Original Message -----
From: Bobby Middleton <bobm@koyote.com>
To: <astro-photo@seds.org>
Sent: Wednesday, January 09, 2002 2:36 PM
Subject: [APML] needed- an excellent sense of direction


> Here's one for the guys with a real good sense of direction. I've got an
> out-of-square focuser on my newt. I know that's the deal because every
time
> when I get the laser collimator perfectly aligned I'll get long stars on
two
> corners of my negatives. These two corners are consistant about having the
> problem, although at times it's worse than others. That means one of these
> corners is too high while the other is too low, right? The normal method
of
> squareing in a focuser is getting a hole exactly opposite of the focuser
and
> aligning the focuser with a laser right on the hole. I have a hole and I
> have it aligned with the laser, but I suspect getting that hole exactly in
> the right place is easier said than done. I suspect my alignment hole is
off
> a bit.
>
> I have not been able to detect my focuser alignment hole's mis-placement
by
> measurement. It appears to be right but obviously something's off. I want
to
> figure it out by N-S-E-W analysis of my camera composition. Here are two
> images typical of my long stars:
> http://www.koyote.com/users/bobm/alnitak.htm
> http://www.koyote.com/users/bobm/ngc281.htm
> Note the long stars at the lower left and upper right of the images.
> If I've got it figured right, these corners are the SE and NW corners.
(Both
> of these images are composed with the 35mm long axis running E-W). Can we
> match this known orientation to my focuser with a description of where my
> focuser is mounted on my tube?
>
> Picture my 12.5"newt on the east side of my AP 1200 mount (ready for past
> zenith tracking). My focuser and camera are on the west side of the tube.
> I'm pointed at NGC 281 (packman nebula) and it's 7:30-9:30 pm which means
> for this time of year NGC281 is about 1-2 hours past meridian. If I get
> directly behind my tube (from tube bottom looking towards NGC 281) the
> focuser will be right about on the 8:00 o'clock position of the tube. Your
> mission, should you decide to accept it, is to tell me which two of the 4
> corners of my JMI 2" focuser need tweeking. To get an E-W long axis
> composition, my camera must lie diagonally with respect to the 4 corners
of
> my focuser. That incomplete description now leaves two possibilities; the
> camera long axis is either horizontal or it's vertical. On my setup an E-W
> long axis composition with everything described as above has the camera
long
> axis composituion with the camera horizontal.
>
> I'm sorry for such a laborous description, but I'm in hopes that someone
can
> get the directional bearings on where my image lies on the film plane, and
I
> can get an idea of which two corners on my focuser are off. I've had this
> mis-alignment ever since I got the newt.
> Bobby Middleton
>
>
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