Hello.
Autoguiding during CCDAP3 works well most of the times. Sometime, recapturing the guide star between the exposures presents some difficulties because the Max Error in pixel is higher than the setted value. As soon this value is reached, exposures starts and session runs. But sometime guiding is not good and the pixel error returns to grow. So The exposure will be not nice. I think the authors could add another one or two attempts to increase the peobability the guide star will be under the setted Max error. Only one attempt could be not sufficient to assure the right guiding.

Thaks

Massimo B.

Hi Massimo,

On the Tracking & Guiding page, if you have Max. error set to your acceptable guide error, and have Max. error cycles set to a number that can be reached within your mounts "settling" time, guiding should start when both those values are satisfied. If the Max. error value is not reached in the specified number of cycles, CCDAP3 will "reacquire the guidestar" by repositioning the mount followed by a plate solve. This should put the guidestar back at the right X/Y location and the guider will start into the Max error routine again. If your guider is starting because the parameters are being met, but your mount hasn't "settled" yet, try setting the "Guide Exposure Delay Factor" on the Light Frames page to a number that represents how many additional guide cycles you want the guider to run before the guiding actually starts. This will give the mount additional time to settle and maybe eliminate your unacceptable exposures. HTH ....

Hi Frank, thanks for your reply.
I have to do a lot of practise with CCDAP and I appreciate your tips. Anyway, the problem I posted is not frequent. Using a small mount as GPDX (I have no problems with my hard GM2000 QCI)some difficulties to get a guide star (during an expsures session) under the desirable Max Error could be a problem. The error cycles in my CCDAP session were setted at 20 by default while the mount settling was 3 sec. I would get a Max Error of 1 pixel. If after 6-7 attempts tha Max Error goes under 1 pixel the exposure stars but than that error could return higher. What settings do you suggest?

Thanks again

Massimo

Hi Massimo,

Because CCDAP3 is an "executive" program, it manages your camera control program. If your guiding doesn't settle down within the CCDAP3 Max. error cycles and stay under the Max. error the majority of the exposure time, then I don't believe the issue is CCDAP3, but back at the autoguiding source. With a smaller mount, things like balance (East heavy for best gear mesh), PEC, quider exposure time, Max/Min move times, mirror drift in an SCT, etc. all play a much bigger role in effecting good guiding.

In my experience, each mount has a "sweet spot" for guide exposure time, and once you find it, until you change something major, varying the aggressiveness in the camera control program for your seeing conditions is about the only change I would make to keep the guiding inside the parameters. I might suggest that you run this particular system without CCDAP3 and turn on the guiding log and capture the data for the situation where the guiding moves below the Max error points and then back out. Change your balance, and do it again, and compare the logs looking for any improvement or degradation in guiding. Have you noticed whether this guiding anomaly happens more often at a particular altitude/azimuth location or is it just random. A random occurrence will be harder to track down of course.

There is a nice tool on the CCDWare site - Auto Guider Calculator V.4. This will give you a good starting point for setting the Max/Min moves to keep the mount from making correction when it shouldn't. The mount electronics and mechanics must work together to produce the best guiding and the electronics can make adjustments faster than the mechanics can handle, so in my experience, its best to keep the guide exposures long enough to let the mechanics make the adjustment, and settle before making the next adjustment. Longer guide exposures also keep you from chasing the seeing.

So after all of this, before I make a specific parameter setting suggestion, let me ask a question if I could. What is the plate scale of your imaging chip, and the plate scale of your guiding chip, and what guide exposure are you currently using, and what is the current settings in the Max/Min move parameters of your camera control program?