Re: 1100GTO not holding polar alignment
Mike, and Joe R.
You might be interested in having an ultra-precise bubble level resting on your mount fork base, to see if there is any rocking of your mount during “daytime slew tests”.
When I suspected the problem, I made an inexpensive level – far more precise than the highest priced ones at a machinery tools supply.
See my write up on the group’s FILES section, with photos, and sources for the part:
There are also some (attached) discussions in the RCOS group thread, about my approach, which you may also find interesting in using my DIY bubble level.
This bubble level tool is a keeper, even after its first use, for the next situation requiring a highly precise “level & motion stability” indicator. Use it resting on the mount base, in both orthogonal directions, to check all motion possibilities. Might be easier to read the already provided (cm. spaced) markings - if you really need to - by painting the pipette’s length along one side, or just sticking on some white carpet tape to it. However, I was more interested in seeing if the bubble actually drifted any amount, even gradually over perhaps several seconds, away from center – indicating a very minor, otherwise imperceptible, shift.
This indication might also not necessarily point to problems with the mount fasteners themselves – but could also point to a minor shift in the telescope’s “ground footing” – such as the tripod’s screwed on levelling feet, or the soil/patio stones, etc. it stands on, as the telescope and tripod weight shifts between extreme sky positions. Something else to consider as the cause.
Finally, you could also tape the DIY bubble level tube to the counterweight bar or mount axle body, as a permanent bubble level for quick manual levelling in the field – doing double duty, rather than storing it away in your kit drawer. Just use something like car radiator antifreeze instead of plain water, to cover winter temperature conditions.
Hope this helps.