Re: PHD 2 Guiding "Good Enough"


Hi John

cancel that - i calculated it at 1.14 arcsec/px

there's a lot of ways to look at this

your guiding right now is pretty exceptional, and the error results in maybe 1/5th of a pixel of error on your images according to your image scale. if you work really hard on improving it, and you get it down by 50% so it averages .15" rms. now the error is 1/7th of a pixel. would you really see that?

If your stars are tight and round (i assume they are) and you are happy with your images, i'm not sure there's much to b gained for you by obsessing on this particular aspect.

On Sat, May 2, 2020 at 8:30 AM John Thompson via <> wrote:
I know this is not a PHD 2 forum but I want to set reasonable expectations of my mount when guiding. Guiding can become an obsession and I want to know when to stop. I have a AP 1600 (no encoders) with a TEC 140 f/7 combined with a STF8300 main camera and an off-axis STi guide camera. I plan to install encoders this summer. I attached a screen shot that shows most of the relevant guiding info from PHD 2. My question is should I be happy with a .23 RMS and a +- .5 arc sec oscillation of the RA. The Dec looks stable and below .5 arc sec. The RA oscillation bothers me a little but perhaps it is "seeing" driven however this is a permanent observatory in a fairly dark site ( 21.6 SQM). I am getting reasonably round stars at 1200 second exposures. I have worked the polar alignment and drift pretty hard. Would appreciate hearing your thoughts or suggestions. I am also posting this to a PHD 2 forum.


Brian Valente

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