Originally posted by Stone G. 
Congratulations with your first O-GPS1 shot! I am VERY happy with my O-GPS1 and regularly uses it with lenses of 200mm to 350 mm focal length. But maximum exposure times stated in the Pentax literature are a bit "optimistic" and critically dependent upon how successful the precise calibration will be from time to time - at least as soon as you go into cropping and/or pixel-peeping.
Thanks!
I did read that the exposure times were optimistic, so I reduced the exposure from what the camera suggested was possible. I calibrated the unit when I first powered it up and got a GPS lock, but when I calibrated it again at night, the calibration seemed to be too quick - it seemed to be accepting calibration even before I completed moving the camera in every axis.
Quote: Actually, with stacking software such as Deep Sky Stacker, you can INCREASE ISO and still cope with the high ISO noise. That will give you shorter exposure times and thus, even less trails. Stacking will not brighten your images but it will improve the signal-to-noise ratio and thus, all kinds of enhancements in the post-processing will be made easier.
Given how much light I got out of the nebula at 400ISO I would like to see what I can do with that speed before I push it higher. With a darker sky and some stacking, I should be able to cut the exposure to say 30 seconds and get better results.
Quote: Looking forward to seeing more results from you and your wonderfull southern skies!
Winter is coming - and the views of the galactic core are best then. However, I'm not sure how well the astrotracer deals with looking toward the pole. This image was taken with Orion almost directly overhead, and I don't think that helped with the GPS tracing. I'm hoping that the GPS will work with my mirror lens and allow some shots of smaller sky features like the jewelbox cluster. I also too a photo last night of Jupiter and it clearly showed three of the galilean satellites.
Originally posted by Bob Harris That is a cool shot Rob, very nicely done. As dark as our desert sky is, this is something I should try.
Thanks Bob! You should definitely give it a go!
Originally posted by DeadJohn My experience with the O-GPS1 calibration has been inconsistent. One shot gives pinpoint stars and then the next trails even when the camera isn't moved between shots. I've had success increasing ISO and shortening the exposure length. Noise can be dealt with during processing (and there's no objectionable noise in the sample you posted, anyway). Trailing stars are much more difficult to correct.
Interesting - I'll have to have a look at evidence of trails when I attempt to stack. I edited the curves quite a lot to eliminate the shadow data, most of which was atmospheric noise.
Originally posted by jbinpg Is this a multiple exposure? Seems that some of the stars in Orion such as Betelgeuse and Saiph are doubled. Same for some of the stars in Lepus below. I agree that the accuracy of the O-GPS1 depends greatly on just how precise the Precise Calibration is. I always do the rough calibration first followed by the precise. Naturally, if your GPS constellation is not that great, the precision will be lower.
It's a single exposure, Jack. Betelgeuse isn't in this image. The bright star in the top left corner is Rigel, and it shows some extension due to the long exposure.
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