DerPit wrote:

ChrisRowland wrote: It seems to me that because the three plate solved positions are reported as unrefracted JNow positions the pole position derived from them will also be unrefracted JNow.

Hmm are you sure about that? The coordinates you get are unrefracted, yes. But what you apply is a relative correction, based on what you <em>see</em>, and that is refracted positions. That's why I assumed aligning to the pole would give you the refracted one.

I'm not totally confident.

AIUI you are saying that because the reference star you are aligning on is refracted the pole position correction must be refracted. I'm very unconvinced about that because the refraction error of the reference star will depend on where the star is. A star that's in the South will have a refraction error that is opposite to a reference star in the North.

It's pretty good when you are getting close enough that you are worying about what pole you want to align to.

Can however well make a difference if you happen to live close to the equator. For me it's already 1.1 arc min, and I'm only at LAT 29

I think that polar aligning to a couple of arc minutes is plenty good enough for a portable set up. Getting better than that would need something like the TPoint method available with the Software Bisque mounts where a precise alignment is determined using about 100 stars, then the mount is adjusted using the high precision mount screws

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