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Old 03-04-2019, 11:18 AM
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Bart
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Automated Focusing and SGP

Before I lose it completely and scream and shout and wave my arms and legs about, are there any SGP gurus on here?

I am once again experiencing issues with SGP and its focus routine. Recently I changed to a 2.5" flattener that I got from a member here, thank you, and focus was still very good.

Last night after a couple of weeks off, I was unable to get good focus. I was getting a dog ear for the first two stars outside of focus with a sharp drop to the bottom which was rounded then the inside of focus was all good with a nice side to the curve but the green lines were not in a good spot so the focus was out.

I've tried to fiddle with all the settings, including backlash, data points, star size, step size and even exposure and binning, yet the curve always resembles the same shape. So....mechanical issue although nothing has changed?

I know what an out of focus curve looks like but the dog ear on one side with the other side going way past is confusing me. It normally focuses well even if the focus is out a bit, and I tried to be as focused as I could before I started.

I am using an FLT132 with a Feathertouch 3.5" focuser driven by a Sharp Sky Pro motor and controller.

Any thoughts much appreciated, before I join Diego with the Voyager software, which I have threatened before.
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  #2  
Old 03-04-2019, 12:54 PM
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Atmos (Colin)
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Could it be that your step sizes are too large?

Another thing I’ve found helpful is to limit SGP to getting the HFD results from the centre 50-75% of frame as any distortions in the other field can play with the results.
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Old 03-04-2019, 01:54 PM
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Bart
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Thanks Colin, step size is 25. How do I limit the frame width?
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Old 04-04-2019, 08:26 PM
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Found it, thanks for the tip. Testing.
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Old 04-04-2019, 09:11 PM
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RobF (Rob)
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Might be good to show a couple of focus run graphs and your settings too....
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Old 05-04-2019, 10:04 AM
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Bart
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I gave it some huge backlash correction and it worked flawlessly last night. Having to add backlash is strange as nothing has changed and has worked fine without it up until the other night.

Thanks for the feedback.
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Old 05-04-2019, 10:33 AM
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that_guy (Tony)
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could you let me know what the backlash correction figure was? I'm having the same issue where the first correction leads to the v curve looking more like a square root sign
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Old 05-04-2019, 01:26 PM
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The Sharpsky Pro driver has a gear box backlash setting, so I set that to 50 steps, up from 25. Your driver may not have this setting.

In SGP I had backlash set to IN and steps at 50. I increased this to 150 steps, to give me a large enough setting to gauge if there was a difference.
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