SharpStar by Lonely Speck

The Precision Focusing Tool for Astrophotography made in the USA.

Achieve perfect focus on the stars with SharpStar.

SharpStar is a simple tool created by Lonely Speck to help astrophotographers achieve critical focus on the stars with their camera lens and filter holder.

SharpStar2 precision focusing tool for astrophotography by Lonely Speck

Focusing a camera lens in the dark is one of the most difficult skills to master for astrophotographers. There’s always the last little bit of uncertainty about whether or not critical focus has been achieved.

SharpStar helps astrophotographers achieve perfect focus on the stars, every time.

How It Works

SharpStar is a special kind of mask that mounts in front of your camera lens.

In astronomy, it’s also known as a Bahtinov Mask. SharpStar uses the properties of optical diffraction to create a set of three fine spike lines around a bright star. These diffraction spikes will shift position as you focus your camera. Adjusting focus so the central diffraction spike sits evenly between the other two diffraction spikes will ensure perfect focus. Once you’ve verified the focus pattern on your test shot, you can simply remove the SharpStar and shoot like normal — knowing that you have perfect focus. Sharpstar is the first of its kind to work on small camera lenses. It has been replicated and copied many times but this is where it was born.

The diffraction spike pattern that SharpStar creates is a precise visual reference of focus success. If the central spike is off to the left, focus is too far, if it’s off to the right, focus is too near. If it’s in the center, it’s just right.

How do I use the SharpStar?

Check out our short video tutorial of how the SharpStar works in the field below:

You can also download a copy of our Quick Start Guide (included with every order).

SharpStar Design

Lonely Speck’s SharpStar is made in the USA. It is precision laser etched optical plastic in California. SharpStar comes in a square filter shape, made to fit into the most popular square filter systems. See below for lens compatibility and filter size recommendations.

SharpStar Lens Compatibility

SharpStar was designed to work on most DSLR and mirrorless system camera lenses. As with most wide field astrophotography, SharpStar will usually show the best results from relatively large-aperture, or “fast” lenses. The shorter the lens, the smaller the diffraction pattern and the more careful you’ll need to be to center your target star in the viewfinder. See our lens compatibility chart below:

In general, the lower the f/number and/or longer the focal length of the lens, the better. (e.g. it won’t work well on a 10mm f/3.5 but will work well on a 12mm f/2). To demonstrate why higher f/numbers aren’t as good, check out the examples below of the diffraction spikes made with the SharpStar on a 16mm lens at different f/number settings:

Example Diffraction Spikes with 16mm Lens

As the f/number increases, the size and visibility of the diffraction spike pattern diminishes. The central spike at f/5.6 is still barely visible, bit it’s a little too difficult to see for us to recommend as a focusing aid. Use the SharpStar at lower f/numbers for the best results.

Mounting SharpStar

SharpStar requires a square filter holder and the appropriately-sized system adapter ring to fit your lens (both items sold separately).

The SharpStar works with the Lee, Cokin, Formatt-Hitech and other similar filter holders that come in 85mm, 100mm and 150mm (NEW!) sizes. If you don’t already have a filter system, we personally recommend the Formatt Hitech system because of its price and its modular design that works well with wide angle lenses: