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Celestron Focuser and SGP

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#1 watty1959

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Posted 17 March 2019 - 10:21 AM

I recently purchased the new Celestron focuser to add it onto my Edge HD 1100. I am also fairly new to SGP.  Does anyone have any experience integrating this focuser into SGP?  I am struggling with the auto focus portion. I've tried various settings in SGP and have not had much luck.  If there is anyone that has been successful at this can you please share your focuser settings that you use in SGP? Thank you.



#2 Alex McConahay

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Posted 17 March 2019 - 11:53 AM

What kind of problem are you having?

 

Can you connect to the focuser, and have its position reading register in the Focus Control module?

 

Have you run the suggested focusing procedures in the manual, the one that helps you set focus position?

 

 

Alex



#3 watty1959

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Posted 18 March 2019 - 04:34 AM

Though the connections seem quite finicky at times, I am able to make the proper connections and manually work the focuser.  I can move it in and out and set a "go to" number and it responds properly. The problem I'm having is when I run the auto focus, after getting as close to focus as I can manually using the HFR values, it never seems to settle into focus. It overshoots and then will reverse and overshoot in the other direction.

 

I have read the manual but I will do so again.  I must be missing something. My seeing the other night was not the best so I wonder if that had anything to do with it. And then I ran out of time with clouds rolling in.

 

Pat



#4 Alex McConahay

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Posted 18 March 2019 - 11:10 AM

>>>>>>  The problem I'm having is when I run the auto focus, after getting as close to focus as I can manually using the HFR values, it never seems to settle into focus. It overshoots and then will reverse and overshoot in the other direction.

 

The way you described this sounds like it is working, actually. 

 

Your graph should look something like the attached image. And you can see that the HFR's start off too large, get smaller, and then get large again. Is this what you mean by "overshoots …..overshoots the other direction? This is what it is supposed to look like. After doing so, it returns to where the focuser was at the bottom of the "V" (actually where the two lines intersect).

 

Or are you talking something else?

 

The final focused shot from the SGP process is not shown. And the last image you see in the focusing routine is the one where the image was too far inside of focus......but that is not where the focuser is any more.

 

Do your finished shots look focused? the ones you take in the camera separate from the focusing procedure.

 

ALex

 

Attached Thumbnails

  • focus run.JPG


#5 watty1959

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Posted 19 March 2019 - 02:05 PM

When I start the routine it takes the image and plots the value. Then typically the next image the value goes to zero. The following image will typically have a value between zero and the first value and ultimately when it runs through the nine steps the trend line is a downward trend and then the routine continues on a new plot. After it finishes the second routine it is still not in focus and starts a third. That is when I thought something was wrong and I stopped the auto focus. Maybe I shouldn't have?

 

I did read the manual again. I will focus with a Bahtinov mask this time and try it again. Maybe I was too far out of focus to start? My original HFR values were about 5 which seemed high but I attributed it to poor seeing. I did not manually go out of focus to determine my step size so that may also be part of the problem.

 

Thanks for your feedback Alex. Hopefully I'll have clear skies at the end of the week and try again.  I will post back my next attempt.

 

Pat



#6 Alex McConahay

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Posted 19 March 2019 - 04:45 PM

Turn off Smart focus. 

 

If you have a line that is heading downwards, but never turns up, it means that you were too far outside of focus to start with. If you are using smart focus, and you tell it to run seven samples, it will run seven, and if it has  not turned back up, it will continue to sample. If necessary it will start all over from where it is, and run even more. 

 

I do not understand how it can go from something to zero. I have never had the readings go to zero. That would mean it found no stars to focus. That does not make sense unless you have huge focuser steps. And if you did that, you would never have that third reading heading downwards. 

 

Yes, do a good manual focus first before attempting any automatic focus. 

 

Me telling you what my focuser settings are is useless. It all depends on the rig, how far your focuser moves per step, your critical focus zone. And such. 

 

Let me explain what the autofocus routine does...….

 

It starts wherever it is. In the above graph, it started at 978. Then it moved three big steps out, and each big step moves it eight little steps. So, it takes a pic at 1002, moves one big step in (8 little steps), and takes another. Etc, as it steps one big step at a time back a total of seven steps (24 little steps in each direction, plus one in the middle where it started) to wind up back at 954.

 

If it finds out in the first three steps that the HFR number is getting bigger, and SMART FOCUS  is running, it tells itself to kick the whole thing out four or five big steps and start again. 

 

In your case, it keeps going, and the number is getting smaller, and so it just keeps going. At some point, it may start a new graph. As long as the number is getting smaller, it will keep doing that. After it starts to turn up, then it can know it has reached focus and is going past. At that point, it returns to where the two slanted lines intersect, and calls that good focus. 

 

This does not explain your second number being a zero. As I said, that is real strange. 

 

So, do a hand focus with your eyeballs and a Bhat mask. And start from there. 

 

Alex



#7 watty1959

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Posted 22 March 2019 - 02:32 PM

I had much better luck last night. I used the Bahtinov mask for an initial focus.  I believe previously I was too far out of focus when I started and my step sizes were way off. Anyway, I did not end up with the perfect "V", but it was not too bad and after taking some images, the stars looked good after zooming in.

 

I appreciate your time in helping me out. That's what I love about this hobby and this forum, people don't hesitate to help one another.

 

Thanks again.

 

at




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