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INDI Library v2.0.6 is Released (02 Feb 2024)

Bi-monthly release with minor bug fixes and improvements

New Bahtinov Mask Assistant Tool

  • Posts: 31
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Thanks for the replies. For the amount of effort required, not worth the reward.
As this is now, it will work best for me when I move to automated focuser.
Equipment

Sky Watcher Esprit 100ED APO
QHY5L-II Mini Guider
Pegasus PPB, DMFC
Xagyl Filter, LRGB+Ha
CGEM DX
RP4.4

William Optics RedCat 51
Star Adventurer
RP4.1
Software
KStars phd2 , Ubuntu, StarTools, Mac OS
AstroDSLR AstroGuider AstroTelescope, AstroImager, Astrometry
3 years 10 months ago #53294

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Is it posible to use the Bathinov Assistant without a motorized focuser? How? I've been able to see the assistant working on previous version occasionally, but since I've installed 3.5.2 I haven't been able to get the assistant working.
2 years 11 months ago #69923

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The Bathinov Mask Assistant is in operation!    Oh wow!   I'll have to look for it!

Right now I do this (a link to my post in this thread):  How I use the Bathinov Mask
 
2 years 11 months ago #69929

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+1 for the non-motorized focuser. Is it possible to do that? Cause I can't see how it could be done :-(
2 years 10 months ago #71102

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Hi,

It's nice to hear that the Bathinov Mask Focus Assistant Tool is used. Here a detailed description on how I use this tool without an auto-focuser.
I don't have an auto-focuser too, so it is definitly possible. The steps are as follows:
  1. Point your telescope to a bright enough star to be able to use your bathinov mask
  2. Place your bathinov mask
  3. Go to the kstars-ekos focus assistant tool
  4. Set the correct exposure time and select detection mode 'Bahtinov'
  5. Take a first shot by clicking the small camera icon next to the stop button to take a single shot
    • A shot is taken and (only the first time after starting kstars) the message window shows a message to select the star to focus on
  6. Click in the photo on the star that you want to focus on
    • After you have clicked the star to focus on a new shot is taken automatically and the bathinov pattern recognition is executed and shown as overlay on the photo
    • Increase the 'box size' so it will contain about 60-80% of the whole bahtinov diffraction pattern. If you choose it too small or too big it will have difficulty detecting the diffraction pattern lines.
    • Verify that the lines of the bahtinov pattern are overlapping the diffraction pattern in your photo, if this is not the case, increase or decrease the 'number of rows' value and take another photo (the 'number of rows' values is used to in a similar way as binning. it groups several rows of pixels in the image to get a better detection of where the diffraction lines are in the image (higher resolution images or a more bold diffraction pattern required a higher 'number of rows'.
  7. Note the two circles with a line in between in the overlay, they are an amplified graphical representation of the HFR. At the bottom of the focus tool the HFR value is shown
    Strive for the smallest HFR possible, preferably less the 1. I usually try to reach values of less then 0.5. Note that an HFR of 0 is almost impossible, that would mean perfect focus, which is hard to do when you are on earth with a thick atmosphere above you :-)
  8. Manually turn your focus knob a little to one direction
    Remember the direction, if the focus becomes worse, the next step you need to turn to the other direction
  9. Press the small camera icon to take another photo
    The bahtinov pattern recognition overlay is shown and the HFR is updated
  10. See if the HFR value has gone down and the distance between the two circles has become smaller
    If the HFR value has gone up, you need to turn the focus knob the other way and repeat the steps starting from step 7
  11. Repeat the steps starting from step 7 until you have reached the smallest HFR value
  12. If you are in focus (reached the smallest HFR), tighten your focus lock screw gentle (if you have one) to prevent your focus from slipping​​​​
  13. Take another photo to verify if the focus has not moved when tightening the focus lock screw
    1. if ok, then you are done
    2. if not ok loossen the focus lock screw a little and repeat the steps starting from step 7 to get back in focus
Note 1: Due to for instance atmospherical turbulence the value of HFR can vary from one shot to anoter. So to be more accurate you can take multiple shots to see how stable the HFR value is. I don't know (haven't tried yet) if the 'Average over number of frames' will do the same. If so, that would be a nice feature :-)

Note 2: When you are using manual focus (pressing the capture single shot button) the HFR graph won't be updated. This is also not the case for any other detection method when using the capture single shot button)
Sometime I do want to use the graph, in that case I press the start capture button (button right of the small camera button). That will take photos continuesly, so you have only a very small time to adjust the focus knob. Since I have an old camera which takes about 5 seconds to download a photo, i have about 5 seconds to turn the focus knob. Another alternative to gain extra time with an DSLR is to increase the mirror lock timeout to about 5 seconds. That will flip up the mirror in your DSLR and wait 5 seconds before taking the shot. Unfortunately that won't work for mirror-less cameras.

I hope this description is clear enough. If you have any questions, don't hasitate to ask. Also improvement suggestions are welcome.

Clear skies!
AstroRunner
The following user(s) said Thank You: Rafa Barberá, Euripides, Rafael Schlegel, AstroMuni, Chris Farrell
Last edit: 2 years 10 months ago by Patrick. Reason: Updated description with some more details.
2 years 10 months ago #71143

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Your description was more than great!

My issue now is if I've done it correctly.

I've started the tool and I've managed to have a small number. Then I took a capture with the capture module (same time, bahtinov on) and there I was way out of focus.
 

Then, I went backward. I've focused on the Capture module with my Bahtinov
 

and then I've started the assistant again. The image was again out of focus. 
 

I do not know If I am missing something
2 years 10 months ago #71180
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Hi Euripides,

There could be several things that went wrong.
First of all, I think you forgot to select the 'Detection method'. That should be Bahtinov. (I know, I forgot to write that in the description. I have just updated it, so it should be there now. See my previous post on this topic in this forum).
Second thing that could be wrong is that the lines in the overlay that the Bahtinov detection method give are not correctly overlapping the diffraction lines in your image. If that is the case, then you need to change the value of the 'number of rows' parameter in the settings. I also added more detail on this in the description.
Third thing is that you can increase the 'box size' so it will contain about 60-80% of the whole bahtinov diffraction pattern. If you choose it too small or too big it will have difficulty detecting the diffraction pattern lines.

When I focus with my bathinov mask, I strive for an HFR of less then 1, peferably as close to zero as possible.

I hope this will help you get you to get razor sharp focus again.

Kind regards,
AstroRunner
The following user(s) said Thank You: Euripides
2 years 10 months ago #71200

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No, I haven't selected anything else than your previous description.

Thank you very much, I'm gonna try again and report back!
2 years 10 months ago #71215

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Ohh yeah, it works! :-) I've rechecked it in my usual way and it is perfect!

Thank you very much for that!
The following user(s) said Thank You: Patrick
2 years 10 months ago #71432
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Great tool @Astrorunner. I do the focussing manually and what would really help is if the tool can visually tell me if I have improved or made things worse by turning the knob (perhaps with an arrow pointing UP, Down). If it was in large graphics, its even better as it would be easier to spot from a short distance as you keep moving back & forth from scope to computer screen. Its just a nice to have :-)
Last edit: 2 years 10 months ago by AstroMuni.
2 years 10 months ago #71640

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Hi AstroMuni,

Adding a graphical indicator if you are turning the focus knob the right way would be a nice feature.

The trend graph that is enabled when in automatic mode (after pressing the start capture button) has an similar function. You can see in the graph if your focus is increasing or decreasing. In the graph you can see if the focus trend is going in the right direction.

I noticed that the HFR will fluctuate around a certain value when you take multiple images without touching the focus knop. The value of the HFR can either increase or decrease slightly due to atmospheric conditions. This means that you need some more captures between each focus change to see if the turn on the focus knob improved your focus.
These variations make it difficult to show in a graphical indicator if your focus change went the correct way after just one or two captures.

That's why I use the automatic mode even when performing manual focus actions. The graph gives me a good indication if my focus is right and if I turn my focus knob the right way.

Implementing a graphical indicator based on a single measurement, might give misleading information, as it might happen that you turned the focus knob the right way, but due to atmospheric conditions, the HFR value stays the same or went the other way. Then the indicator will show that you should turn your focus knob the other way and you see in your next measurement that it got even worse.

But I will put my thinking cap on :-) and see if I can find a solution for that. I do agree that for manual focus such an indicator can be a good improvement.

Thanks for the feedback. Suggestions are always welcome.

Kind regards,
AstroRunner
The following user(s) said Thank You: AstroMuni
2 years 10 months ago #71644

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Perhaps you could compare it with whatver HFR value was showing just before the capture took place or take an average of the values (if its possible ofcourse) :-)
Another nice to have would be if there was some way to 'calibrate' it to understand if the focusser was moving in or out and then be more intelligent in suggesting what the user should do!
2 years 10 months ago #71647

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