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ghilios / joko.nina.plugins

NINA Plugins
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Option to use eccentricity for focus?? #13

Open JohnHawkes opened 12 months ago

JohnHawkes commented 12 months ago

Hi there

Is it possible - or would it be possible - for HOCUS FOCUS to minimise eccentricity as an option over FWHM? No matter how well I collimate my RC I always have a small amount of astigmatism which exhibits as eccentricity either side of perfect focus. At the moment using FWHM hocus focus gets me real close but a slight manual adjustment is needed to get me bang on and get perfectly round stars.

Thanks

John

ghilios commented 12 months ago

No it won't. Hocus Focus doesn't use FWHM for focusing - it uses HFR. That's because you can't fit a PSF to an out of focus star. Eccentricity also requires fitting a PSF.

Instead I recommend you use a Region of Interest (ROI) to exclude the corners where astigmatism will be the most extreme.

JohnHawkes commented 12 months ago

Thanks. I've already restricted the area of interest to the central portion of the image.

Out of interest how come a PSF can't be fitted to an out of focus star? Processes like the DynamicPSF and standard deconvolution and scripts like PSFImage and AI like BlurXterminator seem to do exactly that.

I was under the impression - possibly misguided- that a PSF is an identifying factor for any optical system in or out of focus with any combination of aberrations.

On Tue, 19 Sept 2023 at 00:47, George Hilios @.***> wrote:

No it won't. Hocus Focus doesn't use FWHM for focusing - it uses HFR. That's because you can't fit a PSF to an out of focus star. Eccentricity also requires fitting a PSF.

Instead I recommend you use a Region of Interest (ROI) to exclude the corners where astigmatism will be the most extreme.

— Reply to this email directly, view it on GitHub https://github.com/ghilios/joko.nina.plugins/issues/13#issuecomment-1724629354, or unsubscribe https://github.com/notifications/unsubscribe-auth/ARVKT3S546GHEXVZAQY4U53X3DMPTANCNFSM6AAAAAA45HGWMA . You are receiving this because you authored the thread.Message ID: @.***>

ghilios commented 12 months ago

DynamicPSF and deconvolution won't work on stars far from focus. If you stay very close to focus, FWHM can work. This is why HFR is more commonly used for focusing systems.

JohnHawkes commented 12 months ago

Hocus focus puts me almost bang on focus, any additional tweaking only needs to be done at that point,

It would be awesome if Hocus focus had a selectable extra step that minimised eccentricity - and possibly other factors - after it has arrived at its HFR derived focus.

I'm sure others would see additional benefits and appreciate such an enhancement.

Thanks for a totally awesome plugin.

On Wed, 20 Sept 2023 at 03:03, George Hilios @.***> wrote:

DynamicPSF and deconvolution won't work on stars far from focus. If you stay very close to focus, FWHM can work. This is why HFR is more commonly used for focusing systems.

— Reply to this email directly, view it on GitHub https://github.com/ghilios/joko.nina.plugins/issues/13#issuecomment-1726772651, or unsubscribe https://github.com/notifications/unsubscribe-auth/ARVKT3XHZYIWEWBXAG4ID7DX3JFH7ANCNFSM6AAAAAA45HGWMA . You are receiving this because you authored the thread.Message ID: @.***>