----- Original Message ----
> From: ulrichkorth <[EMAIL PROTECTED]>
>
> --- In [email protected], John Mahony
> wrote:
> >
> > ----- Original Message ----
> >
> > > From: ulrichkorth
> > >
> > > Hi John and Chris,
> > > I think I'v got it now. Our mount is parallactic.
> >
> > Huh?
> Parallactic - better known as polar mount?... Ulrich
Actually it's best known as an equatorial mount (but these are "polar aligned",
so in modern computerized fork mounts that can be used either way, it's common
to use the terms "alt-az mode" (when used without a wedge) vs "polar mode"
(when used with a wedge)).
> >
> > > So CdC sends RA
> > > and Dec to mount controller, which then will calculate AltAz
> > > regarding time. Mount then goes to AltAz. As this will last some
> > > time, controller has to recalculate AltAz. When target is
> reached,
> > > normal guiding in Az will start.
> >
> > If it's only moving in az, it won't track objects across the sky.
If it's an equatorial mount, it should be tracking in RA (az will be changing,
but the rate will depend on where in the sky you are). And with an equatorial
mount you really shouldn't be using alt-az coordinates at all. The mount
matches the sky's natural coordinate system, so why bother converting back and
forth to alt-az? That just gets confusing, especially with the time
relationship involved. The mount's encoders should read hour angle and dec, so
all you need is the time relationship between hour angle and RA (RA and HA look
the same, but HA is fixed relative to your location- 0 HA is the meridian- and
the numbers increase to the west, not east).
-John
