[JohnH]

This is (I hope) the penultimate post on this journey. I repeated the drift test with the relased version of PHD 1.5 - and found that the staircase effect was back. To put it another way sub pixel guiding still does not work with this combination, I have shared that information with Craig Stark and he has some ideas but not time to impliment them as yet. So I still have insufficient resolution to guide accurately with PHD. To confirm this I reverted to Guidemaster and the LPI and got good results, then I added a barlow and it got better (fitting a barlow to a WO66 has a thread all of its own...).

Of course this way I am limited to very bright field stars and have a tiny fov - not good really and the reason I bought the OSS in the first place.

The good news is it worked well, encouraged I tried the LPI with PHD and that worked well too both allowing the LPI to be used in long exposure mode. Still it is not sensitive enough.

Having found and confirmed my issue as insufficient resolution in the guide system I faced a choice - new guide scope (more appature and greater FL) or a new camera (bigger chip, more pixels, mono). Having thought about it before I re-examined the Qguider and this time took the plunge and ordered one. I was very happy to see that it will be supported in Guidemaster v2.

So while I am waiting for that to arrive and the moon is close to full I reverted to the OSS on the Barlow and tried defocussing to help PHD with centroid calcs but it did not improve the situation.

I finally reverted to the Maxim EE software which does centroid well - but bins 2x2 - the barlow reverses that in effect giving me 3.43" / pixel but guiding to about 0.7" which is what I wanted in the first place. Of course I have fov issues but the cam is sensitive enough (just) in this config to give me a guidestar most places with a 2-3s exposure. The remaining problem is the horrid Maxin EE software that insists on selecting the guidestar for you - and will of oten choose a hot pixel - but the reults were most encouraging - my focus was off at bit but I did a run of 3 10 min shots with no failures and round stars at full res of the 20D with no FR in place ...did a bunch of 3 and 5 min shots too, all good. Attaached is a tottaly untouched crop of the middle of one of the 10 min shots at 100% res shot in Large/fine iso200 full moon, the bright star is Alp TrA - I got equally good results on the ecliptic too.