SharpStar by Lonely Speck (original design)

SharpStar2 Now Available for Pre-Order!

Our new SharpStar design is now compatible with many wide angle lenses. Order your SharpStar2 here.

Original SharpStar supporters: Get 70% off your SharpStar2 order

A great big thanks to all of our original supporters. SharpStar2 would not have been possible without your support! Just contact us to receive your unique discount code for your SharpStar2 order.

SharpStar Precision Focusing Tool by Lonely Speck

The original SharpStar design shown here is no longer available in the 85mm size. Limited quantities of the 100mm are still available. Order SharpStar2 here.

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.

SharpStar in 85mm Formatt-Hitech Aluminum Modular Filter Holder

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 the astrophotographer 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.

Read the SharpStar FAQ


SharpStar Focusing Mask

Lonely Speck’s SharpStar is made of precision laser cut plastic and comes in a square filter shape.

SharpStar kits are currently sold in either of two sizes (85mm or 100mm) at the bottom of this page.

Lonely Speck SharpStar Size Comparison 85mm and 100mm

SharpStar is made to fit into the most popular square filter systems including: Cokin P, Lee 100mm (4-inch) or Formatt-Hitech 85mm and 100mm filter holders (sold separately). Please note that final SharpStar products may look slightly different from our prototypes shown here.

Lens Compatibility

SharpStar was designed to work on DSLR and mirrorless system camera lenses. SharpStar will usually show the best results from relatively large-aperture, fast lenses with an f/number rating of f/2.8 and lower. See our lens compatibility chart below:

SharpStar Lens Compatibility-Recommendation

SharpStar (original design) is not recommended for most slow ultra wide angle lenses nor most lenses shorter than 35mm, unless the lens features a very low f/number. SharpStar2 will work on slower, ultra wide angle lenses. (View SharpStar2 here.)

Read the SharpStar FAQ

BONUS: CrossStar Effect Filter

CrossStar Effect Filter

Included with every order of Lonely Speck’s SharpStar (original design) is the CrossStar Effect Filter. Please note: Orders for SharpStar2 (new design) do not currently include the CrossStar Effect Filter. CrossStar will allow you to create cross-shaped diffraction spikes on the brightest stars for that classic star shape in your astrophotography (see sample image below).

CrossStar Example - North American Nebula

Mounting SharpStar and CrossStar

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

SharpStar in 85mm Formatt-Hitech Aluminum Modular Filter Holder

If you don’t already have a filter system, we recommend the following systems:

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


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


SharpStar and CrossStar 85mm Kit

The original SharpStar design shown on this page is no longer available in the 85mm size. Limited quantities of the 100mm are still available.

View our new design, SharpStar2, here.

For answers to common questions, please see our SharpStar FAQ.


SharpStar kits are available in two sizes:

  • $50 for the 85mm Kit
  • $60 for the 100mm Kit

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 100% refund.

Your kit will include:

  • SharpStar Precision Focusing Tool
  • BONUS: CrossStar Effect Filter (not included with SharpStar2 orders)

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