Guiding issues - seem resolved....

[adamsp123]

....until the next issue happens.

After much more fiddling - my guiding graph is running pretty darn flat over the last few runs, just a gentle "bibbling" along.

Here is what I have done.

I am using straight through finderscope with a QHY5v on board.

Flexture ... kill it dead!!! I got a 50mm finder bracket from S&S astroboot, fixed that firmly to a modded dovetail that fits across the scope rings opposite the mount dovetail. I ditched the plastic screws and I use steel ones. Scope is tight in the rings and cables to the QHY5 are strain relieved around the mount dovetail, a little tug on these will send the guiding ballistic.

Next all other cables, camera, power and dew control are also carefully managed.

Now to my PHD settings

2000ms is the step length - gives me about 20 steps in RA and 8 in DEC. 65-75 RA aggressiveness, 25 hysteresis. This is through a Vixen Starbook which also has its own settings so these will be different on other mounts.

Now I have min motion set to 0.05 pixels and the DEC step set right down to 30ms, this 30 setting seems to have stopped completly my DEC guiding "twanging" all over the show. (note I have a permanant setup and my polar alignment is pretty good if not so well aligned 30ms may not be enough)

With a RA inbalance - east heavy and 2 inbalances set on my Mak Newt in DEC - camera heavy with scope horizontal and camera/focuser/finder (not guider!) CofG offset so vertically the scope tries to move also by the front end going down (don't overdo this or PHD won't calibrate!). I did the vertical inbalnce trick to stop the bad DEC wobble I was getting when the scope was near zenith, the simple front end heavy doesn't work so well then.

In use after calibration I stop the guiding then restart (without futher calibration) this seems to settle the guiding down much quicker in my case as the DEC cal has an overshoot when it starts the guiding and it has trouble then getting the star back to the cross hairs, "this off - back on" routine fixes that.

Just thought to share this with you .....until........ - hope not!

Pete

[themos]

I wonder if a hairdryer blowing hot air in front of the aperture (not too close!) will be good at testing guider response...good stuff

[adamsp123]

With the new PHD software you can change some of the settings on the fly rather than stopping it and going through the Brain.

Guiding last night was still good but got even better when I reduced the DEC max to 20ms so only tiny changes to the DEC was possible by PHD the result was the graph went really flat at 4 sec exposure, the guidestar stayed spot on the crosshairs for hours.