How to Make [Legit] Diffraction Spikes on Stars with a Refractor

“Legit” may be a strong word…but…let’s get real.

Learn how to easily create diffraction spikes on stars in your deep-space images without having to pull any magic tricks out of your post-processing hat. It’s dead easy.

To start with, I have to admit I am a bit of a purist when it comes to astrophotography.

I’m not a crazy purist, but I don’t like adding anything to my images that isn’t in the data in the first place. I’ll push, pull, and enhance what I shoot, but if the pixel isn’t there, I’m not comfortable adding it in. Star spikes are something that several astrophotography software packages give you an option to add in after the fact, and while they certainly look nice, to me they are too fake (because they are), too perfect…not real.

That being said, there is a very wide grey area of artistic license in the astrophotography world. At the core of it is scientifically accurate data, assuming it’s acquired properly. However, there comes a point where too much data manipulation can make the final image less scientifically accurate, and I get a little blurry eyed when it comes to that. But, I digress. That’s a discussion for an entirely different day!

What are diffraction spikes?

Shown to the left in this exposure of the bright star Antares, diffraction spikes are artifacts that show themselves on brighter stars in our images when the beams of light entering the objective end (the business end) of your lens run into an obstacle and are interfered with and bent, causing the light to spread out.

So yes — we are capturing an image of the bending of light. There’s nothing like messing with photons in the middle of the night to get your juices flowing!

In this short tutorial I’ll show you how to create this phenomena in your images if you are using a refractor telescope or a normal lens. We have the power, we can bend the light! There is no spoon!

Now, if you’re imaging with a telescope that uses a secondary mirror held in place by a spider (a metal cross piece), you already get them, like this. If you’re not, and would like to play around with it…read on.

Why would you want to do this?

You might want to create diffraction spikes on your stars because you think it’s pretty, and that’s okay.

I did it for two reasons — I thought it was pretty, but, I also knew I was going to be imaging a target that was…a little boring. It was an area around a bright star in Cygnus, Sadr, with not a lot of nebulosity but quite a few bright stars that I thought needed a little window dressing.

How to create diffraction spikes

It’s really, really easy. And, if you’ve got a deductive train of thought, you likely already know how after reading the above section about what diffraction spikes are. Regardless, keep reading to find out if you’re right!

What you need

• A thin piece of wire, approx 1 or 2mm thick. I’d recommend the A or D string from a guitar. It should be about 2.5 times the diameter of your telescope/lens objective in length.
• Some thin cardboard, like a cereal box
• Duct tape (of course)
• Wire cutting pliers
• Scissors or a sharp box knife

How you do it

1. Cut a cardboard into a strip 3cm wide and ~3cm longer than the outer circumference of your telescope’s objective end.
2. Wrap the cardboard strip around the objective end of your telescope, and use tape to secure a collar around it. (Don’t tape the scope!)
3. Cut the wire in half to create two pieces that are about 6cm longer than the diameter of your telescope objective.
4. Tape one end of a piece of wire to the collar you just made, and stretch it across the telescope objective, just tight enough so it doesn’t bend or warp. You just want it nice and straight, and secure it to the other side of the collar with more tape.
5. Stretch the other piece of wire across the objective, making sure it is perpendicular to the first piece of wire. Secure with tape to the collar.
6. Done! Shoot some stars!
7. Seriously, that’s it.

It really works!

During my testing, I took some test exposures to see how well it worked before I committed. Needless to say, I was happy with the results. Most of these images (except for Sadr) are very unprocessed, and all were taken with the exact method and setup shown here.