Astro tracer, works great on exposures where you are attempting to capture a static image, example Milky Way. Here you want no movement i.e star trails as the trails will blur the shot and the Milky Way itself will blur with just a normal exposure much past 25 seconds. Astro tracer will allow much longer exposures, up to 5 minutes, brining in a lot of more light on distance astro features. On average I will expose in the 1.5 to 2.5 minute range. Note, that with a wide rectilinear lens, (like the 15-30), the edges of the image will still blur (or trail) since astro tracer can't accommodate the wider lenses. So keep the feature of your shot as centered as possible if you are using a wide lens.
Astro tracer, to me, is one of the main reasons I moved from Nikon (D810/D750) to the K1, as I can expose night shots at a much lower ISO, thus less noise and more details. Overall an excellent feature, when combined with the GPS.
Make sure you have a green signal on the GPS, and I always go ahead and re-calibrate the GPS if I move more than 15 feet. If your image is still showing movement in the center at 1 to 2 minutes then you should consider re-calibrating the GPS.
For star trails, you really don't want astro tracer, as it will defeat them.
For star trails, I would recommend you stack multiple exposures, instead of one long exposure. Stacking will allow you to pull in a lot more of the fainter stars and give you a better over image especially if you work with partial moonlight to help illuminate your foreground (something I always do).
Here is a short article I wrote several years ago, but it can give you some ideas on setup/capture and post processing on the star trail type of photography.
So far I have gotten about 1.5 hours on a single K1 battery, which is not quite long enough for a good star trails session, so I will use the grip with another K1 battery. The grip with AA NiMh, does not perform well at all. The K1 does not see the batteries with a full charge and only gives you around 30 minutes before you get a low battery warning, whereas with another K1 battery, you can easily get 3 hours.
You will need to use a intervalometer to stack. The K1 has a intervalometer, but I am not sure it if allows a timer function, (most DSLR's will only go to 30 seconds max with an internal intervalometer. There as many 3rd party ones on the market, that plug into the mic port on the K1.
09/23/14 Using Stacking for better Night Photography results @ Photos Of Arkansas
Paul Caldwell
Here is a vertical shot from late summer and you can see slight movement towards the top of the frame, again since I used a 15mm lens. Illumination done with a lantern.
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