PHD2.6 QUESTIONS

[rober...@insightbb.com]

I used PDH2.6 for the first time last night, Been using 1.7 for years with no problems. Last night went smooth also. Observatory mounted cgem with ES127mm apo. Orion SSAG guidescope.  Just did 120sec subs. All look good' round stars. My focus was just a tad off' but it was the first night with my new ES .7X REDUCER imaging at f5.25.

 

  My question. today I looked at calbration results and some guiding no.  Would someone explain what they meen.I would be much appreciated. And thanks for looking. I am using on camera right now. ST-4 cable not ascom yet.  Bob Thanks

 

RA STEPS 13         DE steps 14

camera angle -0.9          Orthogonial error 1.8

 

RMS ERROR

 

0.37  (0.98)                   0.28  (0.74)

 

Total 1.23          RA OSC 0.51         

[Andy Galasso]

Hi Robert,

RA STEPS = number of calibration steps taken to move the guide star at least 25 pixels in Right Ascension

DEC steps = number of calibration steps taken to move at least 25 pixels in Declination

guidance:  aim for ~12 steps on each axis to ensure an accurate calibration.  Use the calibration step calculator to chooses an appropriate calibration step size.

camera angle = angle (in degrees) of the guide camera sensor's X axis relative to the mount's RA axis as determined by calibration

guidance: informational only. PHD2 will accommodate any camera angle.

orthogonality error = angle in degrees between the measured declination axis angle and the ideal angle 90 degrees from the RA axis.

guidance:  any value more than a few degrees probably indicates a questionable calibration (bad polar alignment?)

RMS ERROR = Root Mean Square error = average distance of the guide star from the lock position, measured in guide camera pixels (the first number) and arc-seconds (the seconds number in parentheses).  The error is displayed for the RA axis and the Dec axis, and the combined (total) error is also displayed.

guidance: the smaller the better :)

RA Osc = RA Oscillation measure = ratio of how often the guide star crosses the RA axis. values close to zero indicate under-correction of RA error; values close to 1.0 indicate over-correction (oscillation).

guidance: 0.4-0.6 is good. Personally I look more at RMS error and almost never pay any attention to this.

Hope that helps,

Andy

[rober...@insightbb.com]

Well thanks Andy for your info.My RMS is high if you want 0. 4 to 0.6. Have to see how to improve this.

[Bruce Waddington]

Hi Robert.  Take another look at Andy's e-mail.  He didn't say you should shoot for an RMS error of 0.4-0.6 - he said that was a reasonable target for oscillation.  What's "good enough" for RMS depends entirely on what you are trying to do with your imaging and how happy you are with the image results you're getting.  With your set-up, an RMS target of 1 arc-sec is probably a more realistic goal.

 

Good luck,

Bruce

 

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