PHD guiding for spectroscopy!

[Gasman]

Hi guys

I usually manually guide for taking spectra through my scope/spectroscope but thought I would have a try with PHD last night and would be grateful if any of you PHD experts could have a glance at this screen grab to see if any of those settings can be tweaked to get a better plot on the graph.  I`m using the latest PHD2 version 2.6.3 with Eqmod to guide my permanently mounted NEQ6 in my observatory with a Lodestar ccd attached to my guide module, in the screen grab view top left is through the Lodestar with the graph plot at the bottom, window top right is the spectrum taken with APT through my Atik 314 on a Espirit 120mm scope. The graph plot seems a bit dodgy to me although PHD did seem to keep the star on the spectroscope slit for 4-5mins. Full moon in the sky last night so maybe not the best conditions to experiment with. One thing I`m wondering about  is if PHD does its NSEW calibration successfully why does it still need user input for some of the variables such as Hysterisis, Calibration step, aggressiveness etc etc??. Maybe some future version will no longer need this user input!.

 

cheers

Steve

[vlaiv]

That looks like pretty good graph to me! Sometimes I wish I could have RMS error like that

One thing you might do is increase guider exposure.

Things that you are talking about, Aggressiveness, Hysteresis and MinMo are there to be tweaked depending on: 1. how your mount behaves, 2. Seeing conditions.

If your mount behaves good - no sudden jitters, smooth tracking, you can set guider exposure to longer, and that will smooth out seeing. One thing that tents to happen is "chasing the seeing". That is bad thing. If your mount is solid and does not have much weight on it and setup is well balanced, DEC line should be fairly straight, just small deviations - it should also be almost horizontal (it will have slight angle to horizontal if your polar alignment is not spot on). If you get jitters on red line like in your graph - this means seeing is bad and it's bouncing guide star around a lot (it can be much more severe, believe me). So try to increase exposure, lower aggressiveness, raise hysteresis, and increase MinMo. Ideally you want your guider to respond only to real star movement, but that is really hard to distinguish from seeing induced motion.

Mind you sometimes you can get graph like that if there is wind - that is something that you can't really help (well you can - put setup behind some kind of shielding - inside obsy). Same as with seeing you would want to minimize guider corrections for motion caused by wind.

[Gasman]

Hi vlaiv

Excellent many thanks for the advice. I've watched a few YouTube's on PHD but none of them mention the adjustments you suggest ?. Really helpful.

Thanks again

Steve