To capture sharp stars, try the new SharpStar focusing tool from Lonely Speck
posted Monday, December 14, 2015 at 10:48 AM EST
Have you ever struggled to achieve sharp stars in your astro images, have you fumbled around in the dark trying to fine-tune your lens? Lonely Speck has a new tool to help astrophotographers achieve perfectly focused stars: the SharpStar.
The SharpStar is a mask that mounts in front of your camera lens and it acts as a Bahtinov Mask. Basically, as you also can see in the tutorial video below, the SharpStar creates diffraction spikes that provides feedback on your focus. There are actually three separate grids on the mask and they each provide angled spikes of diffraction. When the middle spike is perfectly centered between the left and right spikes, then the star is in focus. If the central spike is to the left of center, focus is too far. If the central spike is instead to the right of center, then your focus is too near.
The video below gives you a rundown on what the SharpStar is, how it works, and how to use it in the field to achieve sharp stars in your images.
The SharpStar is not compatible with all lenses, however. As you can see in the video above, Ian Norman of Lonely Speck is using a Sony A7 II and Sony FE 55mm f/1.8 lens. More popular lenses for astrophotography, such as the Rokinon 12mm f/2 APS-C lens and the Nikon 14-24mm f/2.8 lenses are not compatible with the SharpStar, although a SharpStarWide focusing tool that will be compatible with wider lenses is in the works and should be available in January 2016. Lonely Speck has created a useful chart to help you determine if your lenses are compatible.
The SharpStar is available in two sizes, 85mm ($50 USD) and 100mm ($60 USD) and is availbale for preorder now for shipping this month. The SharpStar kit also comes with a CrossStar Effect Filter which will give the brightest stars in your images a diamond shaped diffraction pattern. You can order your kit here.
Even with perfectly-focused stars in your night images, you may also encounter comatic aberration. Check out our article about how to easily remove comatic aberration from your night images.
(Seen via ISO 1200)