It doesn’t matter how long you’ve been doing astrophotography, focusing on the night sky is always the most challenging aspect of creating nightscapes. Our standard advice over the years has been using live view, zooming in on the brightest star, and manually focusing until the star becomes a sharp point of light. Sounds simple enough, right? It is simple and works well most of the time, but I have lost count of how many times I’ve been just slightly off, and a millimeter off matters a whole lot when photographing the stars, precision is of the utmost importance.
I’ve tried other focusing filters that are supposed to aid you in focusing, but I never found one that actually worked. That is until I tried the Focus on Stars filter. This is a tool that you place in front of your lens using a filter holder that comes in standard filter sizes of 100mm or 150mm. You use this ‘filter’ temporarily to help you find focus, it works by using a unique laser etching on the filter that creates a pattern in live view when looking at a bright point of light.
Below is what you see when you look at a bright star with this ‘filter’ on the lens. In the gif you can see how the pattern changes when the focus is changed on the lens. All you have to do is adjust the focus manually until the pattern is balanced so the spikes on the side are the same distance on each side of the star. It’s simple and crazy accurate.
I even tried this on my Fujifilm X-T3, if you’ve attempted night photography on a Fuji you know the struggle. Since you cannot zoom in very far on the LCD it’s very hard to see if you have perfect focus. While it was still hard to see on the Fuji, this did make it much easier. Gabor (the creator of Focus on Stars) offered some invaluable advice to pick up a loupe to help with the focusing. He recommended the Carson 10x Loupe which is one of the best additions to my bag after this focusing tool.
The only issue with this focusing filter is that you do need a filter holder system to hold it in place. Not a big deal if you have a lens with filter threads, you can use the NiSi v7 Filter Holder with a 100mm filter, or any other filter holder. The problem is, many of the best lenses for night photography have a bulbous front element which do not allow use of these screw on filter holders. NiSi also has filter holders for these lenses, they are a bit more bulky and a fair bit more expensive, but if you are serious about your night photography it is worth the investment to ensure sharp stars. Below is a list of the most common lenses with links to the corresponding filter holder.
- Nikon 14-24mm f/2.8G
- Nikon Z 14-24mm f/2.8 S
- Sigma 14-24mm f/2.8 DG
- Sigma 14mm f/1.8 DG
- Sigma 20mm f/1.4 DG
- Rokinon 14mm f/2.8
- Rokinon 14mm XP f/2.4
- Rokinon AF 14mm FE f/2.8
- Tamron 15-30mm f/2.8
If you’re serious about night photography this is a must-have piece of gear. It makes focusing so incredibly easy at night that I have no hesitation in recommending this tool.