Focusing Aids

Bahtinov Mask | "easy-sharp" Focusing Mask | Bahtinov Mask for the eVscope (2) | Bahtinov-Maske for the PS 72/432 | Links

Both with my Atik Infinity camera and when photographing with the projection method, I have problems with focusing the telescope reliably. I therefore bought two focusing aids on the AME2018 astronomy fair in Villingen-Schwennigen, Germany: a Bahtinov mask from Lacerta and an "Easy-sharp" focusing mask from noctutec.

Note: I cannot report any experiences here, because I never used these masks in practice and sold them together with the Explorer 150 PDS in early 2020.

However, with the eVscope that I received at the end of January 2020, I got a Bahtinov mask, which is inserted into the tube cap for storage. And in May 2021, I purchased a Bahtinov mask for my PS 72/432 refractor from TS-Optics, because I was having trouble focusing the images with the newly acquired ASI224MC camera. I will briefly introduce both masks at the end of this page.

 

Bahtinov Mask

Photo: Bahtinov mask (Lacerta, for 150 mm aperture), delivered with 3 clamps

From the product description (from Astrogarten, translated):

How to use the mask (from Astrogarten, translated):

A photo of what a correct setting looks like can be found on the product page on the Astrogarten Website (author: Nils Kloth).

At my first attempt with this mask I saw the "spikes", although not always evenly bright. The focusing with the Bahtinov mask seems to have worked to some extent. But this was just a short test on the eyepiece. The "easy-sharp" mask, which I also tested, seemed to be more "stable" and easier to adjust.

Note: I cannot report any experiences with the mask, because I never used it in practice and sold it together with the Explorer 150 PDS in early 2020.

 

"easy-sharp" Focusing Mask

Photo: "easy-sharp" mask (noctutec, for 150 mm aperture)

Description (from noctutec, translated):

Procedure (from noctutec, translated):

Photos of how to approach a correct focus can be found on the product page of the noctutec Website (provided by the Volkssternwarte Köln).

At a first attempt with this mask, I saw the above-mentioned three stars offset by 120°, and also how they superimposed. Focusing with the "easy-sharp" mask seems to have worked. But I cannot remember the 6 spikes anymore... Anyway, this was just a short test on the eyepiece. The "easy-sharp" mask seemed to be more "stable" and easier to adjust than the Bahtinov mask, which I also tested. That is what the advertising claims!

By the way, the mask was too tight to fit into the tube of my Explorer 150PDS. That is why I temporarily held it by hand. This was announced to me by the dealer when I bough the mask.

Note: I cannot report any experiences with the mask, because I never used it in practice and sold it together with the Explorer 150 PDS in early 2020.

 

Bahtinov Mask for the eVscope (2)

Below, I present some photos of the Bahtinov mask for the eVscope (2). For storage it can be inserted into the tube cap. When in use, it is inserted into the tube alone.

    

Bahtinov mask inserted in the telescope lid

 

Bahtinov mask next to the telescope lid

 

Ditto, other side

 

Bahtinov mask put on the eVscope tube

I have become accustomed to focusing the eVscope with the Bahtinov mask before observation sessions and sometimes even in the course of them. It is too easy to touch the focus control during set-up and misadjust the focus. And due to temperature changes or because hit the focus control while observing, the focus can also change during an observing session. Adjusting focus with the Bahtinov mask* takes a little time and effort, but it is too bad if all you get from a session are blurry photos!

*) To do this, move the telescope to a bright star and make the pattern created by the Bahtinov mask symmetrical. Here are examples of sharp and fuzzy settings when using the Bahtinov mask (brighter star accessed, Live View mode):

 

Blurry

 

Blurry

    

In focus

 

In foucs, enlarged (tap on the screen 2x)

Update: While I sold my eVscope in Spring 2022, I bougth an eVscope 2 with the same type of focusing aid.

 

Bahtinov-Maske for the PS 72/432

In April 2021, I first borrowed an ASI224MC camera from a starfriend and later bought it from him, which I also wanted to use at my PS 72/432 refractor. However, first tests showed that focusing a camera is even more tedious than focusing visually. I therefore was looking for an approach that provides a clear criterion for optimal focus. This is offered by the two masks described above, but since only the Bahtinov mask was available in the required size, I ordered and received a TS-Optics Bahtinov mask (mid-May 2021). First tests with the mask at the PS 72/432 looked promising!

         
         
   
         
   

 

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06.12.2022