Gear Review – Focus on Stars Filter

Photographers always have their eye and ear out for a gadget to help make a task easier.

It is often a quest not unlike the search for the Holy Grail.

Photography is a combination of artistic creativity with often high technical requirements. A fusion of left brain/right brain as it were. Some types of photography offer a higher challenge than others. Night photography is one.

As I lean heavily towards night photography, I have a penchant for locating and trying out gear that can help achieve better and quicker results when I am fumbling in the dark on a quest for stars. One such find is a focusing filter created by another night photographer in Hungary by the name of ,Gábor Takács. He has developed filters based on the Bahtinov mask but specifically geared toward photographic lenses. I purchased 2 of his filters, the 100mm and 150mm WIDE filters for lenses in the 14-50mm range and he included his new TELE focus filter, geared toward telephoto lenses in the 30-600mm range, requesting feedback on his newest filter. This post is specifically about the TELE filter, though the WIDE filters function the same way.

Bahtinov masks are used to help focus telescopes. I have used one for many years on my own telescopes with great success. I have also used them on my wide-angle and telephoto lenses but with marginal success and substantial frustration. Achieving a sharp focus on a star has its challenges and it is one of the hardest difficulties of astrolandscape photography and astrophotography. Gábor’s “,Focus on Stars” filters work similarly but as they are made of glass and not resin or plastic, they offer a distinct diffraction pattern that is easy to see on your LCD and subsequent test shot. This makes for a speedier focus setup. The 100mm filters can be used in any 100mm filter holder and the 150mm filters with any 150mm filter holder. The filters work perfectly with my Benro filter holder kits. ,Learn more about achieving pinpoint stars.

Tests

Below, are 3 frames shot on a Nikon Z9 and Samyang 135mm lens using the TELE Focus on Stars 100mm filter. The frame below shows the diffraction pattern on an unfocused lens. The diffraction pattern is uneven. Quite out of focus.

Second test shot (below).

Below is the 2nd shot, zoomed in via Adobe Bridge. The diffraction pattern is much improved, but there is a slight offset of the pattern which denotes there can be more improvement.

Below, is the third shot.

Below, the third shot is zoomed in via Adobe Bridge. The center diffraction pattern is evenly distributed. The lens is now in focus.

I was able to achieve focus in a very short span of time and with only three shots. Amazing!

Above, the Pleiades open star cluster, after focusing with the ,Focus on Stars TELE focus filter. Single frame, cropped in. ISO 400 f/2.0 60 seconds, tracked. I used the Benro Polaris Astro to track. ,Learn more about this amazing tripod head.

Note that this focus filter doesn’t require the use of a tracker to achieve pinpoint stars. Without using a tracker, the ,NPF rule would come into play.

Below, is a cell phone shot of the TELE Focus on Stars filter in a Benro filter holder. (The white line on the top right is a reflection, not on the filter).

,Notes

  • Select a bright star or planet to focus on, such as Rigel, Sirius, Jupiter, etc. Especially for the WIDE filter.
  • Be sure to position the selected star in the center of the frame.
  • Zoom in and adjust the focus until the diffraction pattern is evenly spaced.
  • Take a shot and look closely at the diffraction pattern.
  • Use an ,LCD loupe (like a ,Hoodman) to help see the diffraction pattern better both during focusing and the test shot.

Summary

I highly recommend these filters to any astrolandscape or deep space photographer that uses camera lenses for the task. What do I like about these filters? Here’s a brief list.

  • They are made of tempered glass.
  • They come in two sizes, 100mm and 150mm and they fit standard square, filter holders.
  • As they are square filters, these fit all of my night glass, including the mighty Nikon 14-24mm, my favorite astrolandscape lens (using the 150mm WIDE filter).
  • These filters actually work.
  • They substantially speed up the focusing process.
  • They lessen fumbling in the dark.

Ordering is fast and easy. I ordered my filters on Sunday and received them in three days. Included with the filters are soft, fabric pouches and detailed instructions for their use. This is one of those gadgets that exceed expectations. I’m really happy with them.

If you have questions about the filters, send ga***@fo**********.com" target="_blank" rel="noopener">,Gábor Takács an email. He’s very helpful and responds quickly.

,Focus On Stars Website

Disclosure: I have no affiliation with Focus on Stars. This review reflects my experience with the Focus on Stars filters.

,Gear Review: Benro Polaris Astro Tripod Head

,Gear How-To Benro Polaris Astro Tripod Head and Polaris App

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Update 3.23.2023

I have been using this filter with longer lenses, in particular local lengths of 500mm and also with an h-alpha converted camera. I will be updating this post with findings using a Takahashi refractor telescope as well as a full spectrum camera. Thus far, this filter has been consistent in refining focus using various lenses and camera bodies.

Below, the calibration pattern on the Nikon 80-400mm @400mm on an h-alpha converted Nikon Z6.

Below, the calibration pattern on the Nikon 200-500mm @500mm on a Nikon Z9.


© Silvana Della Camera

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