May 12

Bahtinov Mask 77mm

My first Bahtinov mask was for the Canon EF 200mm f/2.8L. On the EF 400mm f/5.6L, I had always problems to recognize the typical pattern in LiveView mode (10x). And in the last few months my images were sometimes a little bit out of focus…

So I decided to buy a new Bahtinov mask for the Canon EF 400mm. It’s a Gerd Neumann 77mm Bahtinov mask (77mm lens filter size) made of black coated aluminum.

I’ve to practice only removing it after focusing… If the lens hood is completely moved back, it turns together with the focus ring. So I’ve to be very careful, when I move out the lens hood back after focusing.

This Bahtinov mask has much smaller and much more slots than my first mask. I was able to made a test tonight and it works like expected… YES! 🙂

The pattern is clearly visible at 10x magnificaion in LiveView on my EOS 70Da.
By the way, it was not the brightest star on the sky 🙂

LiveView EOS 70Da

11 comments

  1. Peter Komatovic

    This one seams to work fine with the EF 400 f5.6 L. But it is not cheap. I have one from Primaluce LAB and the pattern is not enough visible. Like my live view is not bright enough. It may be becasue it was the first EOS XXD with this featurue.
    https://www.primalucelab.com/astronomy/bahtinov-masks/bahtinov-masks-focus-aid.html

    • star-watcher

      I’ve also a similar mask like yours, but also the pattern is not clear visible on the 400mm. This one really works as expected on the 400mm. I think the finer and the more slots, the better the pattern in LiveView is visible. And right, it’s one of the most expensive masks on the market. But it’s made of CNC cutted black coated aluminum. Very light and solid. Since I’m not equipped with tools to produce a mask by myself, I think it’s a good investition (And I don’t want create paper/carton masks and change them after every usage). CS

  2. Jan Schubert

    Hey,
    Das ist absolut eine lohnende Investition. Schon alleine die Gewissheit, nach einem langen Abend, das man im Focus war, ist das Geld wert!
    Fehlt nur noch klarer Himmel! ;D
    Jan

    • star-watcher

      Sehe ich auch so 🙂 Bald noch eine Heizmanschette dazu, dann nie mehr Tau… Jetzt brauchen wir nur endlich mal wieder klaren Himmel 😉 CS, Karol

  3. Peter Komatovic

    True to have the precise focus is a lot harder with the 400 then with the 200 mm. With the 200 mm it is fairly easy without a mask. I agree that a good mask is a good investment. I’m also looking to get an ASI224 camera for planets so it would also help here. But I must see which mask to use on my Samyang 650-1300 lens which has a 95 mm filter thread.
    CS Peter

    • star-watcher

      Yes, with 200mm focus was not a big issue. I don’t know if I need glasses 😉 but my last few images wasn’t perfect in focus. Hope for tonight to do a first test with the new mask. Weather’s looking good 🙂
      I think you’ll need a plastic mask for your Samyang, because I’ve not seen an aluminum mask with 95mm filter thread… Anyway, take the one with the most/finest slots. I think you’ll get the best result.
      CS, Karol

  4. Miquel

    Hi Karol,
    I got the same mask as you did and I’ve been doing some tests with it. It’s definitely a very high quality Bahtinov mask. I had a question about focusing with the 400mm. Which magnitud stars do you find easier to focus with? I noticed that if I use a big star like Vega or Arcturus, these stars seems to have a significant flares and light fluctuations which it fees like it makes the focusing a bit hard, but I guess if I get a star that is too small, then the bahtinov spikes will be too faint. How you found a good way or ideal magnitud to do the focusing with the mask? Thank you

    Miquel

    • star-watcher

      Hi Miquel
      I would say the best magnitude to focusing with the 400mm is between Mag 2 and 4. For example I used the star 62 Cyg for the North America Nebula. It has Mag 3.7. That was easy.
      For Andromeda I used the star HIP3881 (Mag 4.5) which was quite harder (very faint pattern). So everything between Mag 2 and 4 is perfect for me. Sadr worked very good too (Mag 2.2).
      Generally the best situation is, when a bright star is in the field of view around the photographed object. So I don’t have to move RA/DEC axis for focusing 🙂 Hope it helps…
      CS, Karol

  5. Miquel

    Hi Karol,

    Yes, very helpful. Thanks for the guidance. 🙂

    Miquel

    • Peter Komatovic

      Hi Miquel,
      I also use the same mask. I have two cameras EOS 40D and a EOS 70D which I bought just a week ago.
      I can tell you that the pattern also depends a lot from the camera. On the 40D the spikes were barely visible also on
      very bright stars like Sadr or even Vega with 0,3 Mag. The camera has a lower resolution LCD and live view compared to the 70D. On the 70D as you can also see above the pattern (spikes) are very well visible. But yes I normally also focus on bright stars (brighter then Mag. 3), so to often you need to move RA/DEC axis ;( if the object you shot is away from such stars.
      What camera do you use?
      CS Peter

    • Miquel Casas

      Hi Peter,
      That’s very useful information too. I use a Canon 40D modified by Hutech, so yes, I have some of the same challenges that you’re calling out.

      Best

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