In this tutorial I'm going to show you how to turn day into night and add stars to your empty night sky to any of your photos no matter what you shot them with.This tutorial is very useful if you are interested in astrophotography but you still didn't overcome the basics of your dslr.
Astrophotography is one of the more complicated branches in photography.If you wanna get a great shot of the milky way or any of the stars,you need to shoot fully manual,and worry about ISO(usually from 800-3200,sometimes even more),shutter speed(from 30 seconds to bulb).Now if you don't even know what some of these numbers mean,you should either start learning how to use your dslr,or grab your smartphone and start shooting some landscape shots in bright daylight,then come here and follow my tutorial because I will show you how to make that smartphone photo look like it was taken with a pro dslr,on a clear night sky.
To make this work,you will need only two photos.One will be the photo you want to edit,and the other photo will be the photo of the stars/galaxy,you can choose whichever you like just make sure it's in high resolution.I got mine on Unsplash
You can turn on photoshop now and open your first photo as the main background.
Now grab the magnetic lasso tool and select everything except the sky,we must eliminate the sky from our photo.
If you did that correctly,you should get something like this.
Now insert the photo with the stars,and align it so the bottom of the sky on your second photo matches the top of the mountains of your original photo.If you tried to align it right away,you probably encountered a small problem - you can't see where it should start because the second photo goes over the first.The splution to this is turning down the opacity of the stars layer,make it around 40% so you see a little bit of both layers.Now align the stars properly.
If you have some parts not looking like they belong to the sky,like I do in the right corner of the stars photo,you can solve the problem by grabbing the clone stamp tool and just eliminate the parts that bother you.You can see how I did it in the video.
The next step is turning you first photo from day to night.I did it in only one simple step.I selected my first photo,the mountains,and turned the brightness all the way down,and the contrast all the way up.You can see how it looks now below.
You may notice that the mountains are not completely dark,but they would really look like that if you were shooting them with high ISO and 30+ seconds shutter speed,maybe even lighter.(You don't have to strictly turn the brightness all the way down,every photo is lighted differently).
Now we need to select the stars layer,and create a hue and saturation layer over it.This step is highly subjective.If you ever looked online for some astro photos you've probably stumbled upon high pallete of colors,because the sky really acts that way when you shoot it with your dslr.It can be blue,pink,green etc.I decided to give this one a greenish tone.
Now I need to do the same with the background layer.Add a hue and saturation layer to it,we need to make the highlighted parts of the mountains have a similar tone as the sky,in my case selecting the blue color gives the most realistic tone.
You are done! If this is all you wanted you can stop reading the tutorial right now,but if you want your stars to move in a circular motion(very long exposure effect) then keep reading.
Make the stars layer bigger than it is right now,because the procedure we are about to do will crop that layer a bit.
After you did that,go to Filter - Blur - Radial Blur. Set the "Amount" to around 8(in my case),blur method to "Spin" ,and choose the quality on your own,I think "Good" is pleasing enough.
It should look like this when it finishes rendering.
Notice that the center of movement is kind of behind the mountains.To achieve a better effect we must press CTRL+T and push the layer up a little,it will give you a better and more realistic look.
The end results processed in Adobe Lightroom:
This is it,you had a landscape photo with a clear sky shot in daylight,and now you have a night time photo with some awesome stars.See you in the next one !