Call to manual Losmandy G11 users/experts

[cesco]

After two deluding years using SkyWatcher AZ EQ6 to handle a Meade 7” ED refractor, I got back to my previous mount, the manual Losmandy G11. I had to have maintenance performed by a specialized firm, and also to inspect the RA and Dec worms bearing screws and Oldham joints most accurately by myself. At last, after a good tweak and regreasing  I reliably got round star images in my frames, without guiding, up to 60 s exposure. I don’t care with longer exposures since I was forced to choose capture of many short shots, useful to increase the combined image S/N ratio, after my once dark sky site was ruined by light pollution.

Still, a tiny RA drift still remains, as visible after capturing a handful of frames. I use the QHYCCD Polemaster for polar alignment, and I move the mount manually when accomplishing rotations of the RA axis forward and backward. The instruction manual strongly recommends not to do this by hand as it requires clutches release, possibly generating axis unset. Since Losmandy clutches do not need to be released for manual axis motion, I disregarded this advice. As expected, the reference star of Polemaster neatly follows the green circle when I put back the scope to home position. When I align by Polemaster the mount already aligned by the drift method I find exact coincidence of the two methods, not as time consumption, of course! PHD2 evaluation of alignement precision rates 3 arcsec distance of the true NCP.

My former expectance with Polemaster was  better precision than with drift align in much less time … well, I get similar precision in much less time. Did I attain the best? Is this residual imprecision I get with Polemaster to be attributed to inherent matters of the mount? Is there any optimization for increasing the precision with Polemaster? Can poor mount leveling affect Polemaster  performance? What about imperfect RA and Dec balance?

Thank you for advice and suggestions.

Clear skies,

Cesco

[wimvb]

On 18/03/2020 at 18:11, cesco said:

PHD2 evaluation of alignement precision rates 3 arcsec distance of the true NCP.

3 arcsecs is as good as it gets, and then some. You shouldn't see any drift in dec during 60 s exposures with such a good polar alignment.