|
Leon, I do not have a G11, I use an EQ6. Having said that, and admitting thereby that I have no hands on with a G11, my point is that any mount (go-to) can only know where it is if you tell it. John G implies that the Gemini can learn from your successive star aligns (I think), but if I have understood him correctly, then it is only masking out polar errors.
Here is the way the EQ6 works. When I do a 1 star alignment and subsequently park, the mount goes to what should be south based on it having been pointed at a known target. But this assumes that it is in fact polar aligned! Question: If my mount was pointing East instead of South, and I did a 1 star alignment, would park set it pointing south? Answer: No. So park depends on me setting the thing up correctly in the first place, because it will drive the Dec axis the required amount to go-to 90deg from where I have said it was, and it will rotate the RA sufficient to bring it to zero hours, again based on where I have said it was.
When I drift aligned, rather than watch a star for just 15 minutes, I used K3ccd tools and a web cam. I turned off Dec drive corrections and tweaked till the star trace oscillated +/- over the center line. There will be a little drift due to atmospherics and various mechanical abnormalities, some slight imbalance etc. I found that chasing these was a waist of time, so I reasoned that they were red herrings and any real Dec drift due to mis alignment would never come back to the zero line without correction. After watching the trace vary +/- over an hour satisfied me that statistically speaking the trace would remain the same over 48 hours ( if possible), there is no cumulative drift even if there is some sporadic drift now and then. In other words my mount is Polar aligned...period. As a result, whenever I start an observing session, I initiate a 1 star alignment. The target star is always well within the fov of the imaging chip, DSI or Toucam to start off with. Once centered, The mount will place any go-to target as near as anything to center. The biggest error I get is if I need to cross over the meridian,(cone error) but even then the target remains on chip.
Now that I am satisfied that my mount is polar aligned, if I were to do the same test as you have done, (all I would see is a %$#@ pine tree) I would need to center the OTA to the mount, not touching the mount to get the star trails centered on the sensor. I venture to predict that any go-to mount that is truly polar aligned will faithfully bulls-eye any target after a 1 star alignment. 2 and 3 star alignments are for field setups where time prevents accurate Polar alignment.
cheers,
Doug
|