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.
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?
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.
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.
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.
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.