Thread: Guiding
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Old 15-09-2013, 12:14 PM
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peter_4059 (Peter)
Big Scopes are Cool

peter_4059 is offline
Join Date: Jun 2007
Location: Brisbane
Posts: 4,144

I've been experimenting with guide settings for the past two weekends having switched to phd2. Analysing the guide log has proved interesting and I thought I'd share some results. The analysis software I've been using is phd lab.

Here are 4 screen shots of phd lab output - two from last weekend where I was using the ED80 and two from this weekend where I was using the 10"newt. All other hardware was the same although my polar alignment was definately better last weekend. The blue plots are RA and the brown are DEC. X axis is time in minutes and Y axis is pixels on the guide camera. The table below the graph on the RA plots shows the peak and RMS errors for each axis. On the DEC plots the table shows the amount of frames with guiding corrections.

I've been experimenting with aggressiveness, hysteresis and dec guiding algorithm. I was surprised to see so much guide activity when the aggressiveness is set quite low (50-55%) and the hysteresis quite high (20%).

Another thing that jumps out is the PE. I've never bothered with PEC before as I thought the guiding would take care of it however I planning to try it next weekend to see if this improves things.

I also tried the Hysteresis dec guide mode this weekend instead of Resist switching (that I've normally used). This has resulted in a lot more dec guiding activity.

What it does show is I'm probably stretching the use of a 250mm guide scope with the Newt due to the difference in pixel scale of the two systems. With the ED80 I'm getting 1.36/0.36 px peak/RMS on the imaging scope however with the Newt I'm getting 2.52/0.81 px.

The overall guiding was also much better when the polar alignment was accurate as you would expect.
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