Somewhere to ask questions about the best way to use SharpCap
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Re: Focusers

Post by nexusjeep » Sun Sep 01, 2019 8:37 am

Hi Ian,

It will be a bit tricky to match my settings as I built my own focuser rack and pinion gearing so it is a bit non standard as I needed to remove any slippage from the original 10:1 reduction. So for information my focuser moves 38,000 steps on the Sesto for a travel of 80mm as I leave 10mm dead either end, this equates to 0.0021 mm per step or near as makes no difference 2 microns per step.

For my APM LZOS 780/130 refractor with the various narrowband and LRGB filters my critical focus zone (CFZ) is between 60ish to 90ish microns depending on the filter in play. For my Autofocus setting I have SharpCap set to 20 steps per focus move so roughly 40 microns per move this will then always give me two focus points inside the CFZ so I should get a nice downward to upward curved on the graph in SharpCap in the CFZ. I take three shots at each position as shot 1 is usually not right as SharpCap currently runs in video mode so every time a frame stops another starts so every time the focuser moves this will happen in frame 1 of the three but the second 2 will be accurate as focuser movement has stopped. I do not do planetary shots so this might affect other frames if individual frame duration is shorter than the focuser move duration. I take fifteen sets of 3 shot samples but move the focuser out then in until it is just not in focus and then run the Autofocus scan in the inwards direction and stop it once the samples pass through the CFZ then tell Sharpcap to return to the best position.

I think I have read that the next major release of SharpCap will have the potential to run the camera in still mode which means that theoretically SharpCap could wait for the focuser to finish moving before initiating the next capture but Robin could confirm this, it would be quite beneficial if this is the case as with narrowband filters it is time consuming to keep losing the first shot on each focuser move but even with this I find that the routine works very well and is far easier than me trying to do it.

Hope this helps.


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Joined: Sun Aug 18, 2019 5:06 am

Re: Focusers

Post by SgtBilko » Mon Sep 02, 2019 5:18 pm

That's kind NIck
Thank you

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