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Re-framing after PHD calibrates

JamesF

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JamesF

JamesF

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Once PHD has calibrated itself and starts guiding I sometimes find that the view in the main camera isn't quite framed as I'd like.

Is there a way to stop PHD whilst I reframe the target and then start it guiding again without recalibrating? Will it do that if I just tell it to stop,

move the mount and then start again?

James

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JamesF

JamesF

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Excellent. Just tried that this evening and it seems to work fine. Also had to fiddle with the step time because PHD wasn't seeing enough movement in the star. That's possibly down to using a finder-guider I guess.

James

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Jannis

Jannis

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Like others have said, just push stop, reframe, then click PHD again. With force recalibration un-ticked, it will contineue to guide as before.

If you move the scope a lot it's always best to recalibrate though.

I also found that, selecting a guide star very close to the target prevents field rotation quite a bit for me at least, as it will more or less try to keep the target centered, instead of a star maybe at far the top right corner of the main cameras sensor.

As for calibration steps - as far as i understood this is irelevant for guiding performance, and is only needed to calibrate the mount movements. So setting like 3-4s or so shuold complete the calibration quite a bit faster with a finder-guider.

Personally i think i use around 2-3s on my 200mm finder and QHY5L.

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IanL

IanL

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As for calibration steps - as far as i understood this is irelevant for guiding performance, and is only needed to calibrate the mount movements. So setting like 3-4s or so shuold complete the calibration quite a bit faster with a finder-guider.

You definitely need to increase the calibration step size for shorter focal lengths (actually the pixel scale, which is a function of focal length and guide-camera pixel size). You should be aiming for the calibration to complete in roughly 15-20 steps in each direction. If it completes in 7 or 8 steps, you may have poor guiding, and if it is taking 30 or 40 steps you can almost certainly increase the step size to save time.

You also need to vary the step size with declination; the closer to the celestial pole, the bigger the step size. I use 2,000 near the equator and 2,500 nearer to the pole for a 400mm/5.2µm setup. More here:

http://stargazerslounge.com/topic/188777-phd-guiding-basic-use-and-troubleshooting/

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James

James

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Once PHD has calibrated I end up stopping and starting it no end of times with no adverse effect :) It's only when I slew to a different part of the sky that I'll make PHD recalibrate.

With my 50mm Mini Borg guider I'm calibrating in about 25 steps with a calibration step time of 2000ms :)

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