For most scope use, CdC (and most any general charting program) isn't really involved in the alignment procedure- once you align the scope using the scope's built-in computer and keypad, CdC merely asks the scope's computer where it's aimed so it can display the position, and it can send goto commands to the scope. It doesn't get involved in how the alignment is done, so pointing accuracy will depend only on the AP mount and its own computer.
But I remember seeing something in the documentation about using CdC with systems where you have 2 encoders and a black box that sends those signals to a computer, but the scope doesn't have its own built-in computer (something like JMI's "Software Guided Telescope" systems). In that case, CdC does the alignment. This is an old feature for basic systems, so I thought it would use just a basic 2-star alignment, not the type of multi-star alignment needed to compensate for orthogonality errors. However I just looked again: <http://stargazing.net/astropc/doc/encoder.html> and it looks moderately advanced- there are settings for mount angle errors. But it's still an early feature based on an old S&T article from the very early days of computerized amateur scopes, so it looks like it doesn't calculate the mount angle errors from star positions- you have to figure them out on your own (Z1 is RA/dec axis perpendicularity error, which should be insignificant on an AP mount. Z2 appears to be optical/dec axis perpendicularity error, commonly called "cone error" by GEM owners, and this is where you get errors mounting different scopes on a GEM without shimming.) You can find cone error in an equatorial mount by aiming nominally to 90 dec and looking through the EP while rotating the scope in RA. Ideally, at 90 dec the OTA is parallel to the mount's RA axis, so the image should rotate around the center of the FOV. If not, tweak the dec to minimize the error, (this removes any error in the 90 dec setting), and what's left is cone error. And I have no idea whether this whole method of connecting to CdC will be compatible with the AP system. Syncing on a nearby star is generally pretty accurate, and easy to do with CdC since you can just click on any star and have the scope move there, and then center, and sync via CdC. For long slews, if orthogonality errors make your pointing bad, you can go across the sky in multiple smaller jumps, syncing along the way. -John ----- Original Message ---- > From: hewholooks <[EMAIL PROTECTED]> > > Patrick or anyone else in the know, > > How does CDC perform with the AP mounts - specifically the AP 900GTO? > > The goto function on the AP mounts reputedly is very dependent on > orthogonality of mount with scope and the system AP uses has no plate > solving capabilities. Since I like to image with different scopes on > my current mount (EQ-6 with EQMOD using CDC), this troubles me since each > scope will most likely be pointed differently when attached to the > mount for the evening. With EQMOD, I can plate solve each time I set > up with a different scope and have accurate gotos - maybe not with CDC > and the AP system. > > I am not a big user of the goto system, but usually will sync on a > star near the object I want to image and the goto is only a few degrees in > distance. With EQMOD, the goto is more than adequate for that > distance, but using CDC with the AP mount....? > > Any practical experience or advice considering the above circumstances? > > Hunter > > > > > Yahoo! Groups Links > > > > ____________________________________________________________________________________ Looking for last minute shopping deals? Find them fast with Yahoo! Search. http://tools.search.yahoo.com/newsearch/category.php?category=shopping
