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Re: How do I use the focussing assistant?
Posted: Tue May 17, 2022 6:39 pm
by StuartT
admin wrote: ↑Tue May 17, 2022 4:12 pm
Hi,
the initial use of SharpCap is designed to be started from one side of focus or the other - then tell it to scan towards best focus. It will go past, get the graph to show a peak/dip and then enable you to do best focus.
Once you have done that once, SharpCap remembers the settings used and the distance the scan needed to show a useful peak. Once that is stored, you can use the 'refocus' button which behaves in the way you describe for NINA. The difficulty with doing that first time is that you have no idea how far to move to get a meaningful defocus.
cheers,
Robin
Ok, so I think you're saying that NINA automatically works out how much to de-focus by in order to run an AF curve. Whereas in SharpCap, we have to do that step manually.
If you have time, I think it would be great to make a demo video on youtube showing how the process works.
Thanks
Re: How do I use the focussing assistant?
Posted: Sat Nov 12, 2022 7:53 pm
by StuartT
Ok I am trying autofocus with the Bhatinov mask. It says it's scanning focus but the triangles are all on a horizontal line. Shouldn't the focus be different at different focuser steps?
- Capture.JPG (526.05 KiB) Viewed 1080 times
Re: How do I use the focussing assistant?
Posted: Sun Nov 13, 2022 4:17 pm
by admin
Hi,
so it looks like all the values are basically zero, which makes me think that the bahtinov mask detection code is not picking up the spikes in the image properly or at all. See this section of the documentation which shows how SharpCap should detect and draw dotted lines along the path of the diffraction spikes :
https://docs.sharpcap.co.uk/4.0/#Using% ... nov%20Mask . Keep an eye on the image shown on screen to make sure that is happening as described - otherwise you may need to tweak camera or focus settings before trying to use the autofocus.
cheers,
Robin
Re: How do I use the focussing assistant?
Posted: Mon Nov 14, 2022 9:23 am
by StuartT
Thanks. I did discover (after posting this) that the graph display can be re-sized and this shows the actual Bhatinov star image. There appeared to be the coloured lines, but they flickered in and out and there was a brief warning in red text coming on and off. But unfortunately it was on screen too briefly to read!
I did adjust the exposure/gain to see if I could improve the image, but to no avail.
I didn't adjust the black level, so maybe that is the solution.
Re: How do I use the focussing assistant?
Posted: Mon Nov 14, 2022 1:42 pm
by admin
Hi,
if the warning was flicking on/off quickly then it sounds like you had quite a high frame rate, which means short exposures, which might be part of the problem - perhaps set the exposure to 1s or so to slow things down.
I expect the warning was either that the analysis of the image could not detect 3 lines from the spikes or that the lines that were detected were not at roughly equal angles.
cheers,
Robin
Re: How do I use the focussing assistant?
Posted: Mon Nov 14, 2022 7:24 pm
by StuartT
aha!! I never even thought of that! Yes, I was trying to Bhatinov focus on a star before doing some lunar, so my camera was running at about 100fps.
(I can't figure out how to work the contrast detection mode, so I slew slightly away from the moon to focus on a star instead)
As soon as this horrible rain stops, I'll try Bhatinov with a longer exposure time. Thanks
Re: How do I use the focussing assistant?
Posted: Tue Feb 27, 2024 5:03 pm
by woldsweather
How do you get SC Focus Assistant FWHM to plot a graph?
Re: How do I use the focussing assistant?
Posted: Wed Feb 28, 2024 10:45 am
by admin
Hi,
if you have an electronic focuser set up for use in SharpCap and connected then it will plot a graph automatically of focus score vs focuser position. If you don't have an electronic focuser, or it isn't set up or isn't connected then you get the default graph of focus score varying with time.
cheers,
Robin
Re: How do I use the focussing assistant?
Posted: Wed Feb 28, 2024 11:48 am
by woldsweather
Hi Robin
Thanks for the reply.
I have a Celestron Focuser and I am currently manually moving the focus in and out in Focus Assistant to get the lowest score.
How do I get SC to plot the graph?
Re: How do I use the focussing assistant?
Posted: Wed Feb 28, 2024 3:09 pm
by kaymann
Checkout the last couple of post in this thread
viewtopic.php?t=5508&start=10