Originally posted by mgbirder I sometimes can not achieve calibration and just use the O-GPS without it (i have found that it does function, but my exposures can not be as long). I really think 5 min tracking time without star-trails is pretty much impossible. I never go over 2 minutes with my Da 14mm.
It is sometimes pretty frustrating not to be able to calibrate the unit. Is there any consensus about the correct way of calibration (speed, sequence of the different directions...)? Sometimes it calibrates very fast, in other occasions I give up after 4 or 5 tries ;-) and shoot without calibration.
Thanks for the kind comments :-)
The O-GPS is definitely one of the reasons i will keep using Pentax.
In my experience its the terrain you're on. My unit works wonderfully out in the sticks or from my apartment window, but works horribly down at the iron-laden shore of the Kennebec River by my house (not that I can use that spot anymore since the town in its wisdom plastered the riverside with streetlights).
I wound up with my best series of shots when I didn't have a tripod at all and had to get creative with rocks and bits of stray clothing to use as a camera support.
No tripod, 90 second exposure, 10mm@f/3.5 and ISO 1600
EDIT: And to show that 'longer' isn't necessarily better, same basic shot, only at 210 seconds. The tracking was spot on, dead center, but you still get insane trailing at the edges when shooting very wide (I assume the same effect would carry through at narrower focal lengths as well, only less pronounced.)
No tripod, 210 second exposure, 10mm, f/3.5, ISO 1600 (only difference from above is the exposure length and the amount of correction needed in post to correct the exposure)