Use manual focus mode and focus until the stars are small and sharp then leave the focus ring untouched until all the trail shots are finished.
Note that modern lenses focus PAST infinity so don't just turn the lens all the way, you must either monitor the focus through the viewfinder (or use live view) whilst manually focusing with the AF switch on the lens turned off.
Well, if focus is the issue, focus on a very distant point during daylight before you do the star trails. You could even mark the setting on the lens. I also suggest doing a search for "star trails" on your search engine of choice. There are many primers out there to do this.
Since it is a VR lens that will be on a tripod, it will have to have the VR on the 'Off' position.
And as Spray said, auto everything needs to be turned off, too.
As Yetibuddha said, there are lots of content to search, but the key to getting good shots will likely be sturdy tripods, the field of view that you have, light contamination in that view, and your patience. Good luck!
Do remember that long exposures will tax your battery and you will probably want to turn off long exposure noise reduction - the camera is pretty aggressive.
I disagree with Mike's recommendation on Long Exposure Noise Reduction (LENR). While the High-ISO noise reduction (HINR) can be pretty aggressive, and is more of a matter of taste, the LENR is only doing a dark-frame subtraction to eliminate hot-spots and other heat-related noise artifacts. Other than the fact it doubles your exposure time (it literally takes a dark-frame with the shutter closed for the same length of time as the original exposure), it does nothing but good things for your image.
IMHO MIke is right. The OP asked about trails, not night sky shots and a 30 second shot followed by a 30 second gap doesn't make a trail, it makes Morse code!
I take my trails with everything turned off and do the NR in post.
Well, there are several different ways of getting star trails, each requires somewhat different technical approaches. I prefer numerous 25 second exposures at about F4 or so, with my 20mm lens. It may be something different with the OP's lens. Stacking the photos, I use Startrails (simple, but it works), at shorter exposures means you don't need to do the LENR. But each of us have our preferences for how we go about doing things.
Crisp cold nights are best, but most people are too lightweight to go out with four layers on and hand-warmers then stand for a couple of hours to do trails!
Comments
Note that modern lenses focus PAST infinity so don't just turn the lens all the way, you must either monitor the focus through the viewfinder (or use live view) whilst manually focusing with the AF switch on the lens turned off.
Have fun!
Since it is a VR lens that will be on a tripod, it will have to have the VR on the 'Off' position.
And as Spray said, auto everything needs to be turned off, too.
As Yetibuddha said, there are lots of content to search, but the key to getting good shots will likely be sturdy tripods, the field of view that you have, light contamination in that view, and your patience. Good luck!
Do remember that long exposures will tax your battery and you will probably want to turn off long exposure noise reduction - the camera is pretty aggressive.
My best,
Mike
I take my trails with everything turned off and do the NR in post.
I have a friend that lives in a remote area maybe I'll visit one of these warm nights.
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