RA Slop Tolerance?
Posted 24 November 2012 - 04:58 PM
Posted 24 November 2012 - 05:21 PM
The best measure would be to look at the RMS error when guiding. Too much slop or too tight a worm engagement would affect the RMS guiding error.
On my CGEM using a 200mm finder, the best I can get is about 0.18 pixels RMS. This amounts to a bit less than 2" of error. Yes it's not too great...
Posted 25 November 2012 - 01:38 PM
Posted 25 November 2012 - 05:47 PM
Posted 26 November 2012 - 09:43 AM
Posted 27 November 2012 - 10:27 AM
Posted 28 November 2012 - 12:54 AM
Depending on the maximum room there is between the retainer and worm you may be able to add a thrust bearing which can reduce binding:
While there might be room on one side of the worm, there is no room on the other side since the standard bearings sit right against the cap with no spare room. It would be nice if the system were designed with enough space on each side for a thrust bearing. It is precisely because of this that the bearings are almost always installed too tightly in the first place which damages the bearings and adds to PE.
Posted 28 November 2012 - 10:04 AM
Ed- I really learned a lot from the Hypertune DVDs.
Posted 28 November 2012 - 10:34 AM
Posted 28 November 2012 - 11:56 AM
In that case the standard bearings could be replaced by tapered roller bearings and then they could be set "Snug" and cure the problem.
For the most part it is still a space problem. While tapered bearings in this size are no impossible to find (they are used in some medical equipment), they are uncommon and expensive. I'm not sure if there would be sufficient benefit to switch to them. Standard bearings are OK in this application as long as they are not over tightened. Taper bearings would have the same problem to some extent in that, if they were installed with too much preload, they would still not work well. However, they night not be as easily damaged since they are designed for the axial load. Another possibility might be angular contact bearing, but again you get into more specialized bearings when you go that way.
Posted 28 November 2012 - 05:27 PM
Posted 01 December 2012 - 11:12 AM