I do know that since I started using the polar scope (and taking
my time doing it) my problems with polar drift circles in my
photos have gone away - not to say my pictures are perfect, but
my limiting factors are other things now :-) You can tell polar
drift circles from other flaws because across a typical photo field
you will see a noticable difference in the streak direction, as
the error takes the form of circles around the guide star (which
is typically a bit off axis from the photo center).
I use a C11 at f6.5 typically with exposures of up to 1h45m. Haven't
used it without the focal reducer since I switched to a Lumicon
Giant Easy Guider (which I HIGHLY recomend).
Pete
>
> Yes, that makes sense.
>
> If I remember correctly, on my polar scope there is a circle in the middle
> and on that circle is a little circle that you place polaris in. It will
> then be properly offset from the dead center of the alignment scope
>
> By doing this, how close of a polar alignment would you estimate one can
> achieve?
>
> ----- Original Message -----
> From: Peter Santangeli <psantangeli@No-Spam>
> To: <sf-bay-tac@No-Spam>
> Sent: Thursday, June 29, 1999 4:48 PM
> Subject: Polar Alignment - First Light: JMI NGT-12.5
>
>
> >
> > Not sure if I am following your description but...
> >
> > Polaris isn't actually at the celestial pole. I forget how far off
> > it is, but I'm guessing that's what your circle represents - the
> > distance from the pole.
> >
> > In my Losmandy scope, there are multiple lines going from the center
> > of the reticles rotation. One of them has a "gap" into which you
> > place Polaris.
> >
> > Two of the other lines have need to be lined up with two other stars
> > (don't have charts with me, so I don't know which they
> > are - the are typically the only other bright-ish stars in the
> > field). These lines too have "gaps" for these stars to be positioned in.
> >
> > Three points give you absolute orientation. Once you have all three
> > stars centered in their respective gaps, you are assured that you
> > are aligned. The patience part come in in that you need to rotate the
> > reticle, then change your alignment, then rotate again, then change
> > again, etc, etc. Eventually you get the rotation correct, and the
> > stars just fall into place.
> >
> > The reticle also has diagrams of the dipper and Cassiopea that help
> > give you a start on the rotation.
> >
> > Does that make sense?
> >
> > Pete
> >
> >
> >
> > >
> > > Here's a polar alignment question for you... My polar axis
> scope has a
> > > little circle in the middle and a position on that circle marked where
> you
> > > are supposed to "place" polaris so that it is properly aligned.
> > > Of course
> > > since it is a circle, I would assume that as long as polaris
> in on that
> > > circle it wouldn't have to be in that spot, since all you
> have to do is
> > > rotate that actual polar axis scope inside the mount for the
> spot to be
> on
> > > polaris..
> > >
> > > Did this make any sense at all?
> > >
> > > Robert. . .
> > >
> > > ----- Original Message -----
> > > From: Peter Santangeli <psantangeli@No-Spam>
> > > To: <sf-bay-tac@No-Spam>
> > > Sent: Thursday, June 29, 1999 12:44 PM
> > > Subject: First Light: JMI NGT-12.5
> > >
> > >
> > > > >.With a focal length this long, even a
> > > > > p.a. scope will not be accurate enough. You'll need to use the
> > > > > drift method.
> > > >
> > > > Not sure I totally agree with this... I find that patience in
> > > > using the polar scope well gives me better results than patience
> > > > in drifting using a C11 at F6.5 or so. Polar scopes can be finicky
> > > > things, but once you get the hang of them you can do some pretty
> > > > decent alignments (again with patience... did I mention that
> > > > patience was required?:-).
> > > >
> > > > I've gone as long as 1hr45m (actually, last weekend) with
> > > > scope alignment with no noticable trailing.
> > > >
> > > > Probably depends on which technique you are most comfortable
> > > > and confident with.
> > > >
> > > > Pete
> > > >
> > > >
> > > >
> > >
> >
> >
>