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Procedure for using a Bahtinov Mask in BYE


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I purchased a Bahtinov Mask (BM) today and tonight went to try it out with disastrous result. I suspect I am doing something wrong hence the request for advice.

I normally use HFD so I am aware of that procedure which is fine. However, I also want to know how to use the BM in BYE.

Before fitting the mask I did use HFD to get close to focus so that I hope the BM method would go smoothly!!. When I fitted the BM and highlighted the BM button on BYE, ( the HFD button was also highlighted it could not be deselected but I ignored the numbers), the electronic BM image was all over the place. I decided to take individual snap shots which resulted on an electronic BM image in the small focus window with an accompanying reading. I repeated this without changing anything and the following images and readings were just random in effect useless. 

When using live view on the actual target (Betelgeuse), and zooming in you could make out a faint diffraction spike but its resolution was not good enough to be used practically. 

Is there some precis advice on using the BM with BYE please?

 

Paul

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No, that is not what I meant.  What I said is that the feature is there, and your millage/experience may vary if you use it compared to the other feature.  The manual already explain step by step how

Paul, if you wish to make use of your Bahtinov Mask, it is best to perform your Focusing on a Relatively Bright Star that is in the same quadrant of the sky.  If your Scope is an SCT without Mirror-Lo

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The following is taken directly from the BYE User Guide:

Let's say that you're using a Bahtinov Mask, the stars are not very bright and live view doesn't show the Bahtinov pattern very well. You decide that you need a
continual loop of two to five second exposures (depending on the star brightness) at the default ISO to allow you to manually focus and achieve evenly spaced
diffractions, based on the image shown in BackyardEOS. Here's how to accomplish that. 

  • Set the exposure settings.
  • Set the number of pause seconds.
  • Enable the loop feature by clicking the Loop button.
  • Start the loop plan by clicking Snap Image.
  • Adjust the focus until you are satisfied with the diffraction spikes.
  • If you run out of time, simply press Snap Image again and repeat the process until you are satisfied.
  • When satisfied that the best focus has been achieved, click the Imaging button
  • or another mode button (don't click Disconnect) to terminate the Frame and Focus mode.
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Bathinov masks are good, and so is HFD and FWHM.

But why use it?  You need to physically add the mask, focus, and remove the mask.

HFD and FWHM does as good of a job, and you don't have to touch your gear.  If you get good result HFD or FWHM, use them and never look back.

Just my 2 cents.

 

 

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24 minutes ago, admin said:

Bathinov masks are good, and so is HFD and FWHM.

But why use it?  You need to physically add the mask, focus, and remove the mask.

HFD and FWHM does as good of a job, and you don't have to touch your gear.  If you get good result HFD or FWHM, use them and never look back.

Just my 2 cents.

 

 

BYE has the Bahtoniv feature specifically built into the premium edition so it must have some merit otherwise why have it in the premium edition when FWHM is also in the standard version? As such it is worth using if nothing else than to compare with HFD as I have used on many occasions. So I am looking for guidance on how to reliably use this premium feature seriously lacking any detail in the BYE manual.

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No, that is not what I meant.  What I said is that the feature is there, and your millage/experience may vary if you use it compared to the other feature.  The manual already explain step by step how to use this feature.

Bottom line is that you are trying to focus, and each imaging train/setup is different.  As such each setup will have a unique 'critical focus zone' that will typically be between 20 and 200+ microns.  Which mean your focus can be off to as much as 200+ microns or so and you'll be at the best focus you can get because your setup can't resolve any further.  Here is a good calculator for CFZ.

In addition, you want to limit to near zero the number of times you touch your gear.... and using a Bahtinov mask means that you'll need to touch you gear twice.... using the FWHM/HFD you do not have to touch your gear and both will get you inside your critical focus zone.  So, the question to ask yourself, given that both FWHM/HFD will get you inside you CFZ, do your really want to touch your gear?

Regards,

 

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Paul,

I have used both the mask and FHWM.  I have found that I rarely use the mask anymore with BYE because the FHWM gets me where I want to be.  However, some folks prefer the mask because it is more "graphical" than trying to minimize a bunch of numbers.  6 of one half dozen of the other...  FWIW, the mask feature was one of the first things incorporated into BYE 10+ years ago when Bahtinov masks were just hitting the mainstream and that is why it was included in the premium edition.  Back then, FHWM and HFD were both pretty jumpy.  Now they are averaged out.

The best advice I can give for using the mask is because of the obstruction, less light gets in so you need to up your exposures (as astroman33 alludes to).  Live view just can't capture the photons so you need to use the Loop feature to make out the spikes stand out better.  It also prevents the jumpiness that you experienced which could be seeing.  I don't know where you are, but the upper level winds have been horrible all across the eastern US (can't really speak to other places) and seeing has been awful even though all the other parameters have been great.

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Paul, if you wish to make use of your Bahtinov Mask, it is best to perform your Focusing on a Relatively Bright Star that is in the same quadrant of the sky.  If your Scope is an SCT without Mirror-Locks, then try for the closest Bright Star to minimize any impact of Mirror-Flop.

Don't chose a Close Double Star as your Focus Star - unless you want to see double.  Don't use a Planet, as the Planetary Disk will bloat and invalidate the BM Pattern.  Don't use Sirius or Canopus, as they will make overly bright and fat bases to the spikes.  And don't use Betelguese as it's bloated size often shows in the base of the spikes.

Good Luck!!

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