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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.
After adding several large two-inch eyepieces and an Explore Scientific illuminated finder scope, my dob was quite top heavy. To remedy this, I added two 18” bar magnets to the bottom portion of the scope. Balance now seems nearly perfect! Got this idea from another post I read a while back on SGL!
Recently I opened my AZ-EQ5 mount for adjusting and greasing.
I did not find any complete tutorial for this nor worm or bearings dimensions. I plan to replace some of those if I have the chance.
Meanwhile, I will add some pics of the disassembly process.
Open the plastic top case. Please excuse the USB hub attached, I did not remove that.
Pull out the cable connectors. Put the top case with the controller board aside.
The bolt inside the green circle can help you remembering or adjusting the belt tension. Loosen down the RA motor screws. Remove the belt. Unscrew the bolts. Remove the motor.
The bolts inside the green circles can help you remember and adjust the worm distance to the RA main gear. Remove the bolts holding the worm case.
Parts: RA main gear, worm case.
Remove the screws holding the encoder board. You get access to the nut holding the worm in place. Remove this too.
Remove the bolts inside the driving gear attached to the worm. Sorry, not the best pic.
You can now proceed to push out the worm and the bearings. No pics for this, sorry.
The bearings are 688Z, 16mm outer diameter, 8mm inner diameter, 5mm width.
Worm dimensions measured with the caliper: 69mm, 36mm.
Hope someone finds this useful.
I'd be interested if the worm is identical to the ones used in the HEQ5.