PHD settings

[pvelez]

I've now managed to get my mount, pc and DSI to talk to each other through PHD.

So my next question for the astrophotography gurus - assuming that your tracking is ordinary (as mine is), how do you set the guiding so it makes little nudges rather than big ones? I set the exposure setting at 1 second so I could get a nice and clear guide star but I suspect that the interval between nudges means that the movement needed to keep things in sync results in star trailing.

Any suggestions?

Pete

[g__day]

I'm interested in this too! By the way grab the latest PHD (beta) and set the mode to resist switching.

Polar align as well as you can, and if you log your run if your corrections aren't random I'd guess either your alignment is off or your PE is high.

I used to shoot for 3.5 - 4.0 seconds corrections on my CG5. The higher quality and better set-up your mount - the longer your autoguiding between steps could be.

My guess is the least frequent adjustments at the minimal rate needed - the better.

[ballaratdragons]

Pete,

1 second doesn't really give time to account for bad seeing.

You may get odd shaped stars because the autoguiding program is chasing what it thinks is star movement. It is actually following atmospheric disturbances.
I use 2 seconds on good seeing nights, and 3 seconds if it is below average. This gives the 'star movement' from bad seeing time to average out a bit. The autoguider is happy with these settings and gives me round stars.

I did try it on 1 second once in medium seeing conditions and I ended up with blurred stars.

Also watch the Aggresiveness levels. Too much and the mount will jerk, not enough and it is too slow to respond and keep up. I use Guidedog and keep the aggressiveness around 80. :thumbsup: I don't know what the scale is in PHD.

[garymck]

Hi,
the best way to objectively see how well your guiding is doing is to use PHD to record logs of corrections, examine them using a program called PHDanalyze - a free program at

http://tech.groups.yahoo.com/group/stark-labs-astronomy-software/files/

this creates graphs that shows how well your corrections are working. For example if your corrections are not aggressive enough, the average will be below the center line, if too aggressive above the center line.

You may also need to play around with Hysterisis settings - my mount for example tracks better with zero hysterisis, or high values above 30, at mid values tracking sucks.

Guiding rates may need to be tried also - my best rate is .75x, with low aggressiveness set to 80, you may get better results on slower settings.

Contrary to many opinions, I have found autoguiding adequately requires a long process of methodical trials to learn what works for a mount best. Change one parameter, record a log for a worm period, examine the log, change parameter, record examine etc etc. After a few nights of this you will know how your mount works and what it's limitations are. Then you can get to the real fun - taking pics...

hope this helps.....

Gary

[pvelez]

Thanks guys - this is all v useful. I like PHD because its so simple, but the Help files are a bit on the short side for humble newbies like me.

I see now that the 0.2 sec default which I had changed to 1 sec is in fact the camera exposure only and has no relationship to the period of time between guideframes. So I'll set this at 2 or 3 sec and see what happens.

I'll also give the PHDanalyze a go.

Once again, this highlights how important it is to getthe polar alignment right.

I'll report back when I get outside next - hopefully later tonight

Pete

[g__day]

New beta release of PHD - I've given Craig 14 suggestions (OMG) - great guy, looks like some will be implemented soon!

But there's a new beta release 1.5.2 available.

http://www.stark-labs.com/depot/beta/Setup_PHDGuiding_152.zip

[pvelez]

Thanks - will download when I get home this evening. I need to do my bit for the drought!

Pete