[jamespierce (James)]

I used TPAS on my Argo/Servocat setup for the first time last night, previous to this I've never bothered. The pointing has always been ok, good some nights, ok others - objects would nearly always fall somewhere inside a 1 degree field and either re-aligning from a near by object or using the Servocat local sync function always tightened things up to search in a region. Last night though I was out a bit earlier, already setup so I figured why not give it a try - the process I followed was thus.

1) Standard 2 star alignment process
2) Turn on sampling mode
3) Sample 4 stars and compute the basic model using only the IE element.

At this point things were better, objects were consistently falling inside a 0.5 degree FOV.

4) Sample about 9 more stars right around the sky using a mag +2 stars tour. The servo cat would drive within about 0.25 of a degree, I'd center, sample that star and move on.
5) Recompute the model with all 5 elements (not sure if I should have used them all with only 13 stars ?)

The whole process took me about 15min and it was my first time. I would say next time it's a ~10min job.

For the rest of the night I slewed all over the sky enjoying a highlights package for the last night of our 6 night observing trip, 50% of objects were dead centre, 40% within 0.1degree of being centred and the remaining 10% were within 0.2 degree. I really noticed an increase in accuracy around the zenith, typically a trouble spot for a dob + argo.

Unless I'm out for a very quick session, or only looking at a very small region of sky I can't see a reason not to do a short TPAS run - it's easy to spend far more than 10min over the course of an evening tweaking the alignment or just chasing down objects which were not found first time. You can do the whole process early in the evening before it's dark enough to view anything properly anyway. It was especially nice to work through a number of very faint galaxies in Fornax with each one dead center, no wondering if you'd found it or not !