Originally posted by schnitzer79 Thanks for the brilliant replies. A lot of useful info here.
Heres what I intend to do. Definitely use GPS and astrotracer on the K-3II. It will be the first time using it as well. We will be going to the location after 10 pm which is an abandoned village with ruins and deserted houses so will want to capture some landscape too along with the sky. The reason I was thinking mostly of the Sigma 35mm is because it is very sharp wide open and will benefit from the f1.4. Just uncertain if at f1.4 any of the foreground will be sharp since I intend of focusing at infinity. Im also not sure if I will need to do any light painting on the deserted houses and trees or if that will ruin the image. I know its a matter of trial and error, just trying to minimize the tries as much as possible, since it will be dark and changing lenses constantly in the dark is not a good idea.
Havent done any stitching before, but I only use photoshop cs6 so I know you can stack images there too if needed, but that wasnt the plan that I has in mind.
Anyone who has tried astrophotography on the k-3II, will I need to do a GPS calibration on the spot prior to shooting? Also any one know how fast the GPS drains the battery?
With the astrotracer you will need to stack foreground and background. To be honest, you should do that without astrotracer as well as the exposure requirements are very different for the 2 elements. To take advantage of astrotracer will mean the foreground is blurred by the moving sensor.
You will need to calibrate onsite, make sure you are not near any iron/steel when you do so as you are actually calibrating the compass, not the GPS! Follow the instructions and don't be afraid to recalibrate later if you keep getting small star trails on sub minute exposures.
My starting point for any sky shot with the astrotracer is 60 seconds, 1600 ISO. If the sky is washed out, I have light pollution and need to decrease the ISO (which means less stars, but that's life). If I have trails I either need to recalibrate or shorten the exposure length. Remember to experiment, especially as this is your first time. You will take lots of shots, you will bin most of them, but you will end your night with something you are happy with and a lot more knowledge then you started with! Play with different lenses and find what works for you, what gets you the sort of image you have visualised. Astrophotography can include quite a bit of personal taste!
For the landscape just take shots with different settings until you are happy. You can easily do very long exposures with low ISO and a sharp aperture in bulb mode (as long as there is no wind). Using photoshop means you can focus on getting the foreground exactly as you want it.