HIGH PRECISION focusing tools for Landscape and Deep Sky Astrophotography

I designed Focus On Stars to use the bright, wide-angle lenses most commonly used in Landscape Astro Photography to allow a precise focus adjustment on the live image alone, even without taking test shots. In a test with a lens that is not very bright but has a very wide-angle (2.8/14 mm), I targeted the star Rigel, which is only the seventh brightest star in the sky. Focus On Stars worked perfectly on the live image already at 10x magnification (Canon EOS 6D).
With brighter or less wide-angle lenses, Focus On Stars can be used to adjust the sharpness of the live image even in the direction of stars with lower brightness.

Focus On Stars is compatible with all standard rectangular filter holders designed for 100 x 100 mm or 150 x 150 mm filters.

Make sure the lens focus ring is rotated to the infinity signal! If your setting is significantly different, the light spots will blend into the background. You can then see at least one three-point line of spots around the star. I will provide a detailed user guide for the product, explaining how the filter may still need to be slightly moved horizontally and/or vertically so that all three line of spots required for focusing are clearly visible.

Adverse conditions may occur: In the case of a cirro-strati or moonlight, the stars are less bright, or the really bright stars may just be covered by a landmark. In this situation, you may not be able to judge the correct focus on the live image. – Make a test shot, in which the position of the light spots will be clearly visible! If the center spot is shifted to the left, the focus is closer than ideal. If it is shifted to the right, it is further away. Accordingly, with tiny shifts in the focus ring, take more test shots until you reach the center spotlight perfectly centered. This will make the image the sharpest. Then remove the Focus On Stars device from the filter holder and take your much desired shot.

The invention made public by Russian amateur astronomer Pavel Bahtinov on an internet blog is a focusing mask based on the principle of diffraction that he developed for long-range telescopes.
Adaptations of this mask to wide-angle lenses have been attempted by several people by laser etching a relatively dense Bahtinov mask into an optically clear plastic sheet. These devices really work great as long as you don’t want to use a really wide angle lens. When photographing astro landscape images with these devices and trying them with wide-angle lenses, the diffraction rays are too small, faint, and thus they are difficult to or can’t be evaluated at all. In addition, it is very complicated to position the selected brighter star perfectly in the center of the Bahtinov mask…
Like all astro landscape photographers, I had the same problems, so I experimented with the idea of Pavel Bahtinov’s mask until I found the optimal solution. I created a very complex, microscopic optical grid that fits into the appropriate filter socket, until it was able to use the much more visible light spots (diffraction maxima) with all lenses instead of the faint and hard-to-see diffraction rays to adjust the focus. A simple Bahtinov mask only works if the target star is exactly at the intersection of the mask’s three-way grid lines. This is easily accomplished when a star is targeted with a telescope. However, wide-angle lenses capture a huge sky surface with billions of stars that are very tiny in the image. Thus, with a simple mask, it is very difficult to place the brightest star selected perfectly in the center of the image and the grid at the same time.

With the complex optical grid solution used in Focus On Stars, it is enough to move the camera or the mask placed in front of the lens by just a few mm to easily get the selected star to one of the grid centers.

For films sandwiched between sheets of glass, e.g. glass slide frames, film scanners, etc., this is an undesirable but still common and natural phenomenon known as Newton’s ring. It is not a defect and does not affect the function of the filter in any way.

Compared to other manufacturers’ products, you can see a more visible, more definite diffraction pattern around the image of the star. This makes the positioning of the selected bright star also much easier.

Here is a comparison where shooting conditions are exactly the same in the following two cases:

How much will I have to pay for shipping in total?

First, at ordering you pay for advance for delivery, supplier is Deutsche Post International Logistic (DHL). Since January of 2022 for customer satisfaction the courier price has been reduced by $ -2..7.

The courier prices in 2023 are remained the following:

$22 – Austria, Croatia, Czech Republic, Germany, Romania, Slovakia, Slovenia
$24 – Other European member state (incl. tax)
$19 – Other European country (Switzerland, Norway and UK, but not Moldavia, Ukraine, Russia)
$25 – Canada, USA
$37 – Africa, Australia, Asian coutries and some Eastern European states mentioned above, including China, India, Japan, New-Zealand and all others.

Second, in some cases additional payment might occurs afterward.
Outside of EU please count addtional duty (over de min-i-mis value, depending on state low)
and/or handling fee at package arrival.

+Good news:
As we experienced, DHL average shipping time is only 4-5 day after packaging, so typically no longer than a week after successful payment.