How critical is PA when you guide...?

[chubster1302]

Was playing around lastnight using NINA and 3 point alignment and got it to 0 0 34" error margin. 

If I plan to guide with PHD2 would that be acceptable ? 

[SteveNickolls]

Not so much as you'd think. Much more explanation here.

Cheers,

Steve

[pipnina]

My anecdotal evidence would suggest that better PA usually results in better guiding. But only to a point. Sub-minute is what i aim for and often get 0.4 to 0.6 total RMS on my belt mod HEQ5 with an overweight (unbalanced) load.

I sometimes forget to polar align... And it ends up 2-3 degrees out. I might still get sorta-ok guiding but not for the 1.2s/pix scale i image at (about 1-1.2RMS common here, plus likely to see some rotation through the night)

[Elp]

That's the key, imaging pixel scale. I pay no attention to specifics and just get it near to 50 or below arc seconds RMS. Works at 135mm, works at 1000mm. You obviously want it as accurate as you can get it so the mount guiding doesn't have to work so hard (it can overcorrect as well as undercorrect).

Edited June 4, 2023 by Elp

[900SL]

Below 1' is fine for shorter focal lengths if guiding. 

Field rotation becomes an issue if significantly out of polar alignment

http://celestialwonders.com/tools/rotationMaxErrorCalc.html

 

[newbie alert]

Your image scale dictates how well you need to guide

Remember if using a separate guidescope and camera the rms figures that you see are the image scale of that, not the imaging scope/ camera..

You will never get perfect PA as we're always looking through our atmosphere, which bends and wobbles our perspective of true accuracy

There's always a conflict between softwares, so say you used Nina, then used say a polemaster and then used the drift align tool in PhD I'm pretty certain they wouldn't totally agree with each other..