Tuesday night I went down to the obs and had a plan to work more on NGC6357 and maybe do Omega Centauri while waiting for the former to rise.
Murphy had other plans though. It seems that separated oil from the worm gear had rolled down the back of the RA gear again and got caught in the homing sensor. This PME has tested my patience and continues to do so. To clean the homing sensor I had to disturb the polar alignment by moving the altitude to its upper most limit. I then pulled the motor off and cleaned the gear and sensor, well at least I thought so. I put it all back together and did a PA tpoint model three times to get alignment and then start a larger model for pointing only for the mount to stop again when it crossed the meridian. I then repeat the procedure of cleaning and once again do another model only for the mount to stop again. On the fourth occassion I was quietly seething. Peter who was visiting was most helpful in holding the torch and got to see first hand what the bowels of a PME looks like. In the end I got the entire gear clean again (I do wonder if this will happen again next year after our hot summers) and even got my PA better than before with Hadar falling dead center of the image and even got 3 hours of data on the Eagle Nebula.
This Ha image is a 100% crop of the central part of the image. Lots more data will be needed to complete the image as a combine of the OIII and SII is quite noisey, however for now I am glad of the mount to be working and pointing well.
Sorry to hear about your issues with the PME, glad you got it sorted at then end.
Although I am not as familiar with the inside of the PME as you Paul, I would probably say that the issues you are having may be to do with the fact that you are either using the wrong grease, or simply just too much of it. It really does not need a lot.
I have had my PME running in Arkaroola since Oct 2011, going from Spring to Summer to Autumn. Upon my last visit in March I inspected the worm gears and grease levels etc and all was good. The mount moved flawlessly and there was certainly no indication the grease was melting away etc. The temperature was in excess of 43 degrees up there on a number of occassions. I was also surprised to see very little dust on the mount.
You are also assuming that the cause of your woes is a dirty sensor due to the grease, given that you had to repeat the process three times without success makes me think there is something else at play here.
Dont discount software causes for this problem, check your software for any limits you may have invoked. Does the problem always occur in the same gear position?
Anyways, good luck and lets hope your last attempt has licked this thing in the butt.
Mark, I have not regreased the mount since shortly after purchase. I did use a liberal amount but not excessive. Well at least I thought so. I did try to follow the tutorial on regreasing on you tube, but being my first time I might have put just a bit too much. The grease I am using is the one recommended by SB that being lubriplate 105 grease. I have seen this before up at Moorook where there was grease dripping out on a warm day of at least 10 mounts.
Your mount is relatively new and you most likely have not regreased yet from factory setup, so you should not have too many dramas yet.
Each time I cleaned the sensor there was oil from the grease. It must roll down the inside face of the wheel and onto parts of the wheel that are read by the sensor, an easy enough task with these mounts I think.
Limits are not an issue, non set, only hard stop. Each time this has happened it is in a different position. However I am not discounting the fact that the homing sensor migh be at fault, that does happen and I don't really know how old this mount is. Perhaps Ken could shed some light on this?
If it happens again I will need to think about other options to solve the problem. Until then let's hope nothing else can go wrong.