Quite some time ago I purchased a used Ultima 8 fork arm setup here on Astromart. As it came with the Byers gears, I was looking for something a little more accurate than the Celestar setup i had. When I installed the tube in the "new" forks, I Used this method to allign the forks.
1) Set the dec to 90 degrees
2) Rotate the tube in r.a. noting the runout as measured at the corrector retaining ring using a dial indicator, especially noting variation parallel to the fork axis. As there is some play in the bolt holes that the bolts go through to attach to the base, it was possible too move the fork arms to adjust for runout. Any variation that I noted 90 degrees of the fork axis (1/4 turn around the tube from the point the fork mounted to the tube) I adjusted the dec to minimize this.
3) Using a dial indicator still, I would then measure the runout on the outside of the corrector cell to compensate for runout that would appear as eccentricity on the dial indicator when rotating the tube in r.a.
4) Continue by trial and error to adjust, attempting to minimize runout as much as possible.I got within about .05 in.
So here are my questions. Is there a more accurate way to do this (allign the forks), and if there are published numbers that specify what would be an accepted variance in alignment. I use digital setting circles (Astromaster) which are pretty accurate but not as accurate as they were when I had this setup on the Celestar mount. I am also looking into getting a better CCD camera for astrophotography (Using the old DSI now, and keep as autoguider) but dont want to put the money into the camera if its not possible to get the mount where it needs to be, or if the misalignment is going to affect the quality of the pics.Though I don't notice any issues with the DSI, I dont go beyond 30 second exposures. Any help/thoughts would be appreciated.
1) Set the dec to 90 degrees
2) Rotate the tube in r.a. noting the runout as measured at the corrector retaining ring using a dial indicator, especially noting variation parallel to the fork axis. As there is some play in the bolt holes that the bolts go through to attach to the base, it was possible too move the fork arms to adjust for runout. Any variation that I noted 90 degrees of the fork axis (1/4 turn around the tube from the point the fork mounted to the tube) I adjusted the dec to minimize this.
3) Using a dial indicator still, I would then measure the runout on the outside of the corrector cell to compensate for runout that would appear as eccentricity on the dial indicator when rotating the tube in r.a.
4) Continue by trial and error to adjust, attempting to minimize runout as much as possible.I got within about .05 in.
So here are my questions. Is there a more accurate way to do this (allign the forks), and if there are published numbers that specify what would be an accepted variance in alignment. I use digital setting circles (Astromaster) which are pretty accurate but not as accurate as they were when I had this setup on the Celestar mount. I am also looking into getting a better CCD camera for astrophotography (Using the old DSI now, and keep as autoguider) but dont want to put the money into the camera if its not possible to get the mount where it needs to be, or if the misalignment is going to affect the quality of the pics.Though I don't notice any issues with the DSI, I dont go beyond 30 second exposures. Any help/thoughts would be appreciated.
It is what it is...
