Is PA seeing limited?

[Earl]

I spent most of last night cloud dodging and refining PA

I got my RA down to .05 and Dec down to .08 out in PHD drift aign, util both 0 pixel

However these figures did have a tendency to dance about abit which leads me to think seeing conditions?

[Scott]

I'm prepared to be corrected here but i'd imagine perfect pa is perfect pa. celestial north is a constant (relatively speaking) not effected by seeing/weather etc. on the other hand, your camera/optics ability to deal with the seeing is not a constant and this is possibly where the dancing comes into it. 

[Earl]

yeah as we are using an optical method with know issues, to give feedback on the process,

a) im not sure the equipment can measure it accuratly due to seeing

b ) is the equpipment actually capable of been fine tuned when we are taliking sub pixel out.

where do we dra the line on PA?

[Scott]

yeah as we are using an optical method with know issues, to give feedback on the process,

a) im not sure the equipment can measure it accuratly due to seeing

b ) is the equpipment actually capable of been fine tuned when we are taliking sub pixel out.

where do we dra the line on PA?

Thats a good point earl. I guess for me, I got it as good as I could and started using it. the guiding graph can vary greatly from one night to another and its on a pier. I just use it and if the stars look round then I'm happy . sorry, not really the answer you're after

[Earl]

of course after the fafing with pa cloud rolled in so i was unable to test the results with a 20 min sub.... typical .

[Earl]

another point im only doign PA with 385mm focal length, with a camera whcih resolves to 4.37"/pixel. (lodestar x2 used lodestar stats on 12dstring)

[Big Jim Slade]

another point im only doign PA with 385mm focal length, with a camera whcih resolves to 4.37"/pixel. (lodestar x2 used lodestar stats on 12dstring)

Yep a longer FL will give you more accurate results. And it will change slightly from night to night, since you are aligned to the refracted pole, and the that will change depending on the atmospheric conditions.

Then there's what type of PA you want - TPoint happily offers up 3 or 4 different alignments depending on the results you're after (better pointing, long exposures etc.)