Pentax Astrotracer & Bulb Mode


Probably Not Walter Kernow
With my recently acquired K-3, I'm keen to try the Astrotracer.

One thing is a little perplexing - it says to use Bulb mode - I can order a Remote shutter release, but I'm curious to know why it doesn't work in other exposure modes (or maybe it does?) and if you can at least combine it with a 2s delay or something to avoid fat-fingers moving the camera? Seems like a strange limitation for something which should involve the least camera-interaction to maximise stability.

Any tips? I've seen a few youtube videos of it in action and most skip over this detail.

Also, how accurate is the GPS? Does it matter if I calibrate the camera 2-3m from the tripod or once its calibrated it can automatically compensate based on live satellite telemetry (or given the built in GPS fudge-factor on consumer GPS data is there a margin of error anyway which is largely irrelevant for astro) ?