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A few points about t-point.
Its best to do it in one night. I am not sure if there is a rule that it must be but I've been told that and it seems reasonable.
If you adjust your mount according to the t-point polar alignment model you need to delete the model and start again after the adjustments.
Before you do the polar alignment model you need to delete outlier points in the model as per the tutorial. Otherwise you get a less accurate evaluation of your polar alignment.
I don't know if all this is now automated with the Sky X t-point.
Read the t-point tutorial as it is quite involved.
You add terms in a certain way and each must lower certain values otherwise you are not improving the model.
You had to have a certain number of points before you start adding terms. As I recall it was 50. If you want large numbers of extra terms you need a large model like 200 points. Again as I recall from the tutorial where it is all specified.
The first terms to try out are mentioned in the tutorial. I found these worked as per the tutorial.
The result is very accurate go-tos (mine aren't dead centre of the image but close to it and the object seems to be not far from the centre of the image of a 16803 camera chip at 2958mm focal length. I am sure I could get mine more accurate.
My polar alignment is very accurate (Around 30-40 arc seconds) but again I could tweak that last tiny bit I am sure. I get round stars at 2958 with PEC. Without PEC there is some minor elongation. I probably could tweak it so there is no star elongation without PEC. But that is a guesstimate.
When you do the PEC make sure you have the east-west button autodetect otherwise your PEC curve will be upside down and worsening not improving. That took me 3 months to spot!
Greg.
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