SharpStar2 Precision Focusing Tool by Lonely Speck

SharpStar2 Precision Focusing Tool for Astrophotography by Lonely Speck

SharpStar2 by Lonely Speck

Precision Focusing Tool for Astrophotography

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.

Trona Pinnacles and the Milky Way

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 Focusing Mask Demonstration

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 SharpStar2 works in the field below:

The original SharpStar is shown in the video above. SharpStar2 works the same way.

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

SharpStar2 Design

SharpStar2 precision focusing tool for astrophotography by Lonely Speck

Lonely Speck’s SharpStar2 is made of precision laser etched optical plastic and comes in a square filter shape.

SharpStar2 is currently sold in four sizes (67mm, 75mm, 85mm or 100mm) at the bottom of this page.

SharpStar2 precision focusing tool for astrophotography by Lonely Speck

SharpStar2 is made to fit into the most popular square filter systems including: Cokin P (85mm),  Cokin A, (67mm), Lee 100mm (4-inch) Lee Seven5 (75mm) and Formatt-Hitech 67mm, 85mm and 100mm filter holders (sold separately).

Please note that SharpStar2 products look slightly different from our prototypes shown here. Your SharpStar may arrive with a protective paper backing that will need to be removed before use.

SharpStar2 Lens Compatibility

SharpStar2 was designed to work on most DSLR and mirrorless system camera lenses.  As with most wide field astrophotography, SharpStar2 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 SharpStar2 on a 16mm lens at different f/number settings:

Example Diffraction Spikes with 16mm Lenssharpstar-f-number-example

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 SharpStar2 at lower f/numbers for the best results.

Mounting SharpStar2

SharpStar2 requires a square filter holder and the appropriately-sized system adapter ring to fit your lens (both items sold separately).

SharpStar2 precision focusing tool for astrophotography by Lonely Speck

67mm SharpStar2 mounted on the Cokin A filter holder (sold separately)

The SharpStar2 works with the Lee 100mm (4″), Cokin, Formatt-Hitech and other similar filter holders that come in 67mm, 75mm, 85mm or 100mm 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:

67mm (lenses up to filter diameter of 62mm):


75mm (lenses up to filter diameter of 72mm):


85mm (lenses up to filter diameter of 77mm):


100mm (lenses up to filter diameter of 105mm):


Order Your SharpStar2 Now

SharpStar2 is available in four sizes:

  • $59 for the 67mm (Formatt-Hitech 67mm, Cokin A)
  • $62 for the 75mm (Lee Seven5 75mm)
  • $64 for the 85mm (Cokin P, Formatt-Hitech 85mm)
  • $69 for the 100mm (Lee 100, 4″x4″, Formatt-Hitech 100mm, Cokin Z-Pro)

100% Product Guarantee

If you’re not satisfied with your order for any reason, contact us and we’ll make it better with a free replacement or return for refund.

Your order will include:

  • (1) SharpStar2 Precision Focusing Tool
  • Quick Start Guide with simple instructions for getting started

NOT included: filter holder and adapter ring (sold separately, see recommendations above)

85mm and 100mm: In Stock. Ships in 3-5 Business Days.


*All orders are currently processed through Celery. (This name may appear on your charge approval.) Credit cards (via Stripe) and PayPal are both accepted forms of payment.

*PureNight orders will usually ship from California, USA via USPS First Class Mail. Tracking may not be available for certain international destinations. All packages sent internationally are properly marked with their retail value and labeled as a “Glass Photographic Filter” with HS Tariff code 900220. You are responsible for any customs fees imposed by your country. 

Questions? Check out our Sharpstar FAQ