[g__day (Matthew)]

I am trying to get PHD tuned so it will allow me to take longer than 10 minute using a 127mm MAK at 750mm focal length into a Meade DSI to guide shots on a 2.3 metre focal length C9.25 into a Canon 400D. At last attempt I was seeing about 1 arc second un-corrected RA drift every minute - so I lept trying and tweaking variables.

Last night I stumbled to the fact setting my RA aggressiveness in the range 50 - 80% on 2-3 second guide intervals wasn't having much effect, so I change the setting to 90% and star trails halved! Trying again with it set to 100% produced first a 10 minute then a 15 minute shot with no star trails!

Moving targets and trying again procudes a box effect (maybe stars were binary and too close) cause I ened up with a strange yo-yo producing a 4 of everything in a tight box effect.

It was around 3:30am so I packed it in but I am definitiely going to investigate this more (hopefully not just with brute force testing).

Whilst normal I guide with settings like:

RA aggressiveness 80% (tried 60 - 80%)
RA Hystersis 10%
DEC guide auto
Min Pixel 1.20 (normally use 1.1 - 1.3)
Pulse guides 1.5 - 2.5 secs

My best results before yo-yo's came back was obtained on a faint star
with settings

RA aggressiveness 100%
RA Hystersis 10%
DEC guide auto
Min Pixel 0.20
Pulse guides 2.0 secs

I guess once flexure is minimised everywhere (the Losmandy side saddle and rings are as tight as I can get it by hand) - its seeing, polar alignment, PEC and paramter tuning for PHD - oh the fun.

So at 15 minutes I get 4 shots and hour to test settings on - slow going!
Can anyone think of a way to speed up my testing (other than vary a setting - try at 300 secs pass / fail - try at 600 - pass / fail - try at 900 pr more seconds?

Thanks Matt