HIGH PRECISION focusing tools for Landscape and Deep Sky Astrophotography

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Wonderful pictures of the night

Everyone is amazed by the view of a starry sky. Wouldn’t you like to capture it all in the finest detail?

The increased sensitivity of today’s digital cameras has made it possible to take pictures of the starry sky, as well as the landscape underneath it.

A taste of my astro-landscape photos © Gábor Takács (Hungary).

Best equipment = perfect focusing?

It doesn’t matter how long you’ve been doing astrophotography, whether you’re a beginner looking to get nice results as quickly as possible, or you have experienced photographer who wants to get the best out of your equipment.

It’s no use having the best equipment and the most expensive lenses - if focusing is not perfect!

Focusing accurately on the night sky is always the first and one of the biggest challenges to this day! In its absence, fine details disappear from the image, while lens aberrations (such as coma and chromatic aberration) are visibly amplified. So even the most promising picture, taken with great effort, becomes at best a vision to be shared on social media, and is useless for more serious purposes.

Why is it difficult to perfectly focus at night?

Despite rapid advances in equipment and post-processing methods, there are still many technical difficulties in producing these high-resolution, detailed images.

In the dark of night, we shoot with high sensitivity, on a tripod, but with a shutter speed of 10-20 seconds max, and an open aperture. The goal is to collect as much light as possible in the shortest possible time, so that the stars remain like dots (the movement of the sky should not be visible).

Since you are shooting with the aperture fully open due to low light conditions, you won’t be able to correct the inaccurate focus setting by narrowing down the aperture which means greater depth of field!

How to set proper infinite focusing to stars on a nightly sky?
The Focus on Stars device is mounted on the lens for a proper night landscape astrophotography.
  • Auto focus (AF) does not work because there is too little light for it. Although some of the most advanced mirrorless (MILC) cameras offer star focusing, the reliability and consistency of this method is less than the accuracy of manual focusing with a magnified live view, which also has many uncertainties.
  • The infinity mark on the lenses (if any) is only approximate! There are many reasons for this: One is manufacturing tolerance, which means that not even lenses of the same make are the same. In addition, today’s sophisticated lens systems are more sensitive to temperature changes, so the exact position of infinity also changes slightly during the day. So the sharpness preset during the day and fixed with a gaffer-tape will be inaccurate at night in the colder weather.
  • For zoom lenses, with the exception of a few parfocal lenses, infinity is elsewhere at all focal lengths. So if you switch from one focal length to another, the lens must be refocused.
  • The method that still works best and is the most common is to aim the camera at the brightest star and manually focus on the live view at maximum magnification until the star becomes the smallest sharp dot of light. It sounds simple enough and often works well, but I can’t count the number of times I’ve slipped a little, and a millimeter counts for a lot when photographing stars, i.e., accuracy is everything!

So I began to search persistently how, by what means I could effectively achieve the sharpness of my night landscapes.

Today, I can set impeccable sharpness with my proprietary tools and more and more people around the world are using them.

Don’t leave it to chance!
certainty of perfect sharpness is now possible!

Don’t leave it to chance!
reassuring certainty of
perfect sharpness is now possible!

Using the magnified live view, these filters quickly and accurately guarantee the maximum sharpness your lens is capable of! … You’ll be surprised by the results!

Focus On Stars WIDE

WIDE filter device for Landscape Astrophotography (since 2020)
for Landscape Sky Astrophotography

Focus On Stars TELE

New TELE filter device for Deep Sky Astrophotography (2023)
for Deep Sky Astrophotography
"The Focus on Stars filter works very well.
Anyone who claims that such focusing aids are not needed probably has plenty of images that are somewhat out of focus - but they don’t know it.
There is a difference between being in focus and being exactly in focus. If they are just a little out of focus, stars may look sharp, but the chromatic aberration will show up on the lenses, and the off-axis aberration will be greatly increased.
A lens that you thought was performing badly can be improved a lot just by finally focusing it properly for the first time."

How the Focus On Stars WIDE and TELE filters work

The “WIDE” version developed for wide-angle and ultra-wide-angle lenses. The “TELE” version developed for telephoto lenses. They are both adaptations and improvements of the Bahtinov mask for camera lenses, used in astronomical telescope.

They can be used in a standard square filter holder (100 mm wide or 150 mm wide) placed in front of the lens for the time of focusing. (Some can manage without a filter holder, simply by holding the filter in their hand.)

If you point your camera at a bright star, after inserting the filter, the magnified live image will show a special pattern around the star (the central spot). The GIF below shows how this pattern changes during focusing:

How to set proper focus on a star through live view (not only slow test captures)

I have good eyes and a modern camera.
Do I really need such a device?

Many people think they are focusing correctly, and yet when they see their somewhat unsharp images, they think buying a new lens is the only solution.

But with sufficiently precise sharpness adjustment, a significant improvement in quality can be achieved. Focus On Stars filters guarantee the maximum your optics can do – at a much lower price!

Let’s look at some practical examples:

Figure 1. I aimed my 2.8/14 mm lens at the star Arcturus

2.8/14 mm lens

I aimed my 2.8/14 mm lens at the star Arcturus (mobile version)
I aimed my 2.8/14 mm lens at the star Arcturus

with Focus On Stars

Figure 2. 85 mm lens and Focus On Stars TELE filter

85 mm lens

85 mm lens and Focus On Stars TELE filter (mobile version)
85 mm lens and Focus On Stars TELE filter

with Focus On Stars

In Figures 1 and 2, you can see with your own eyes how much easier and more reliable it is to accurately judge the pattern of Focus On Stars filters than to estimate the size of the stars, i.e. when they are at their smallest.
In the top row of images, in the middle three images the difference in size between the stars is barely visible. Maybe because you are young, have good eyesight and your camera has a great live view, you can still see it, but for most people it’s a big uncertainty with a lot of errors.
Don’t forget that in reality you can’t see the phases side by side like this, so you can’t directly compare the size of the stars! So you can rotate the focus ring back and forth until you hope to find the smallest star. However, this is mostly just hope, and the results are usually far from optimal, and even in the lucky case they are between “a little too close” and “a little too far”.

Focusing is a piece of cake!

So instead of vaguely estimating the size of the star, here’s a sure method to get the best sharpness:
Simply observe the position of the 3 bright spots relative to each other, that you’ve gotten with the Focus On Stars tool. If the three spots are equidistant from each other (the shape is symmetrical), then the focusing is perfect.

The most effective focus setting for the starry sky: use Focus on Stars device
So simple: if the shape is symmetrical, the sharpness is also perfect.
"I spent some time with your Focus On Stars filter and my Canon R5 on a dark night in a dark place. The R5 is amazing for night work.

The thing that surprised me is that the filter gave better focus than focusing without the filter! I knew from experiments at home that it is faster to focus with the filter than without, but I thought the results would be the same. They were not.

This surprised me because the view through the view finder with the R5 was really good. I thought I had really good focus. I tried a simple experiment. I first focused with the filter and took a shot, then purposely defocused, then focused without the filter and took a shot, defocused and repeated, alternating between using the filter and simple manual focus. Each time I would make one exposure. I later checked the results on my computer. Using the filter always gave slightly but obviously better results, no matter how careful I was without the filter. I am convinced the filter is a great thing, especially for cameras that do not have as good a view finder as the R5. It is too bad it will not work at 11mm f/4.

I will be modifying my documentation and recommending the use of Focus On Stars. I see a lot of sample images from my users that could be improved if the stars were in sharper focus and the Focus On Stars filter is a good tool for improving the focus. Great product."

Focus On Stars WIDE - for
landscape astro­photo­graphers

How was this tool born? For years, I’ve wanted to finally find a way to really get the sharpness just right.

While researching the literature I found some promising devices on the internet, which are also recommended for wide-angle lenses by their manufacturers. They are all very similar: the well-known grid lines of the Bahtinov mask were laser-carved into a plastic sheet, relatively densely. They are available in square format or as a screw-in circular filter. I have tried a few of them. Although they work really well with longer focal lengths, I was disappointed using wide-angle and ultra-wide-angle lenses used for landscape astrophotography. The pattern was too small and too faint for any of them to be useful for my 2.8/14-24 lens.

So I started developing my own product. After much experimentation, I have created a focusing device that is ideal for wide-angle lenses, and with this optimal solution, I have made the life and work of many landscape astrophotographers easier and more efficient.

See how I use it!

This optimal solution ensures an impeccable sharpness for your astrolandscapes, it will be a special helping device for you too.

Since the appearance of my new invention on the market in 2020, Focus On Stars WIDE has proven to be a real niche product. Due to its unique design, it is currently the only focusing device that actually works with a lens up to 14 mm! It can help to prevent a lot of disappointment. Not to mention the wasted time and the unrepeatable photo/weather situations.

Focus On Stars WIDE is available in sizes 100 x 100 mm and 150 x 150 mm.

Focus On Stars filter devices with bracketed Lens and DSLR camera
Focus On Stars filter devices in bracketed Lens and DSLR camera

Its ideal operating range is 14-50 mm, but with really bright planets and stars it can be a useful help up to 150 mm.

You can even use it with a high-speed (f:2.8 or faster) 12mm lens, as long as the live view image from the camera can be magnified up to at least 12x.

„If you've read my previous article on the Kase SharpStar Filters, then you know a Bahtinov Mask is a great way to focus at night! However, there's one problem - these filters don't work well with wide angle lenses (35mm and wider). The wider the focal length, the less visible the diffraction spike becomes. This is where Gábor Takács' Focus On Stars filter comes in. …

My final word is that the Focus On Stars filter works as advertised.  You can see diffractions spikes all the way to 14mm!  If you're tired of getting home and finding out that all of your photos are blurry, this might be a worthwhile investment.”

Focus On Stars TELE - NEW!

It is true for everything in the world that no tool can be equally good for all purposes – and this is also the case with focusing filters.

First, I designed the “Focus On Stars” filter specifically for wide-angle lenses. Until now this was the only product available, but with the introduction of the new (TELE) filter, it is now called WIDE for clear differentiation. Although this filter is great for focusing with even 150 mm lenses, it doesn’t work in the usual way with fast lenses above 50 mm (f: 1.4-2.0). With these fast lenses, the displacement of the central spike between the two edge spikes is difficult to detect because each diffraction spike is further divided into many parallel spikes. Focusing is perfect when they are covered again.

This is illustrated in the figure below, where I use the “WIDE” version with a 1.8 / 85 mm lens.

illustrated in the figure below, where I use the "WIDE" version with a 1.8 / 85 mm lens.
illustrated in the figure below, where I use the "WIDE" version with a 1.8 / 85 mm lens. (mobile version)

Focusing with WIDE filter on telephoto lens

As you can see, the WIDE filter can be used well with longer focal length lenses if you know that the focusing is correct when you see the thinnest possible pattern. So the aim here is no longer to eliminate asymmetry when adjusting sharpness. This will work with really bright stars.

Focusing with lenses around 50 mm and above is much more comfortable with the new TELE filter!

Focus On Stars TELE for 30-400 (up to 600) mm lenses!

Focus On Stars TELE is designed for those who alternate between using different longer lenses over 50 mm

Focus On Stars TELE is designed for those who alternate between using different longer lenses over 50 mm with a star tracking device (such as the revolutionary BENRO POLARIS).

The aforementioned plastic-plate engraved filters from other manufacturers actually work at the same focal length, but have limitations compared to my more convenient new product.

What are the benefits of Focus On Stars TELE?

Focus On Stars TELE differs from similar filters on the market in that

  • It has a much finer and more regular optical grid.
  • This will make the diffraction spikes larger and brighter, with a more defined contour.
  • This means you can focus well not only on the brightest star, but also on the faintest one, so you don’t have to rotate the camera on the tripod further away.
  • At 100 mm and above, the filter is less sensitive to positioning, so it can be simply held in your hand in front of the lens, without the need for a square filter holder!
  • Around 135 mm and above, there is no need to enlarge the EVF live view!
  • The tempered glass surface is scratch-resistant and smooth, making it easy to keep clean.
  • In addition, the filters come in a well-padded and stylish protective pouch.

The point is: you don’t have to fiddle with it as much in the dark. This makes focus adjustment much faster and more accurate.

Once you’ve experienced how easy it is to work with my Focus On Stars filters, you’ll stick to this experience.

A taste of the effectiveness of Focus On Stars TELE:

A taste of the effectiveness of Focus On Stars TELE:

A live view of an old Canon EOS 6d Mark I (DSLR) from ten years ago with a Samyang 2.0/135 mm lens.
The target star was the central star in Orion’s belt, with an apparent magnitude of only 2.1!

„Carrying around another filter in my bag, just to check my focus, seemed at first like a waste of space, time and money.

However, as I get older I've found my eyes don't see to focus as well as they used to. This problem is echoed by many of the people in my nightscape workshops. So many of my friends have missed getting the shot-of-a-lifetime because their images were slightly out of focus.

The Focus On Stars filter makes precise focusing so easy! It creates a unique pattern that is much easier to judge focus symmetry than any other Bahtinov style mask I've tried, especially when using the more difficult to focus wide angle lens we typically employ in astro-landscape photography.”

Which one should I choose?

Focus On Stars TELE (100 x 100 mm)

For 30-400 mm tele lenses with filter threads. Usable in a 100 mm square filter holder (e.g: Lee 100mm, Cokin Z, Haida 100, Nisi 100, Formatt-Hitech, Benro, etc.) or even hand-held in front of the lens.

Focus On Stars TELE (100×100 mm) precision focusing device for Deep Sky Astrophotography

JUST U.S. $110

Choose the size(s) that suit your needs – see below and above.
In addition to product charges, you only have to pay advance the shipping costs which needs for delivery given at the next page.
After payment on the next business day supplier (DHL) will pick up your package and you can follow it by tracking code given in e-mail.

Focus On Stars WIDE 100 x 100 mm

Suitable for 14-50 mm lenses with filter threads. Compatible filter holders: e.g: Lee 100mm, Cokin Z, Haida 100, Nisi 100, Format-Hitech, Benro, etc.

Focus On Stars WIDE 100×100 mm precision focusing device for Astro Landscape Photography

JUST U.S. $125

Choose the size(s) that suit your needs – see below and above.
In addition to product charges, you only have to pay advance the shipping costs which needs for delivery given at the next page.
After payment on the next business day supplier (DHL) will pick up your package and you can follow it by tracking code given in e-mail.

Focus On Stars WIDE 150 x 150 mm

Fits 14-50 mm lenses without a filter thread, with a fixed lens hood and a highly convex front lens. Examples:
Nikon 2.8/14-24, Tamron 2.8/15-30, Sigma 2.8/14-24, Sigma 1.8/14, …

Focus On Stars 150×150 mm precision focusing device for Astro Landscape Photography

JUST U.S. $165

Choose the size(s) that suit your needs – see below and above.
In addition to product charges, you only have to pay advance the shipping costs which needs for delivery given at the next page.
After payment on the next business day supplier (DHL) will pick up your package and you can follow it by tracking code given in e-mail.

SPECIAL OFFER!!!   Discount packages!

Buy a TELE filter together any WIDE filter, you will get the TELE filter with a discount -25 USD!

WIDE 100 + TELE (100) =
only U.S. $210!

or / and

WIDE 150 + TELE (100) =
only U.S. $250!

Choose both the size(s) that suit your needs – see above. Buy even 2 TELE with each size of WIDE! You may order for friends – only 1x delivery fee! 

After picking products above (with “I CHOOSE THIS” buttons, at Checkout page every pair of products will decrease the amount of payment.

Common additional features:

  • Focus On Stars is protected by scratch-free tempered Gorilla Glass.
  • I packed it in a labeled and padded case sewn to its own size, keep it in it after delivery!
  • I provide a 40-day, 100% buy-back guarantee.
40 days guarantee

A perfect solution

Use Focus On Stars in front of your lens to:

  1. focus quickly and accurately,
  2. take photos with very wide-angle optics,
  3. if you’ve tried a similar device (e.g. a mask) before, but weren’t happy with the results because it didn’t work with your wider-angle lens.

Visit special places where the starry night sky offers an inimitable wonderful sight, capture it and show it to others!
Now you can capture it as the SHARPEST picture possible. Show it to the world!

Frequently asked questions and answers

I’ve gathered the most frequently asked questions about Focus On Stars. If you can’t find the answer to any of your questions, please contact me at gabor@focusonstars.com

Gabor Takács (Hungary) inventor and member of naturArt Photographer Association

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:

Left image

A ray of light from a star under the influence of a simple Bahtinov mask etched on a plastic plate.

Right image

Focus On Stars diffraction image for a perfect focusing.


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.