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han59

Autofocus for Moon, Sun and planets in CCDCiel 0.98ß

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For info:

The latest version of CCDCiel (freeware) introduces autofocus for the Moon, Sun and planets. The principle is the same as with autofocus for stars. For planets however, it measures the sharpness of the image instead of the half flux diameter of the stars.

Feedback is appreciated. icon_smile.gif

Han

ccd_ciel_focus_planet.png.b8798ce2391252b6cf6ab449d3d04a76.png

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Can't wait to have a try, the weather isn't playing nice ay the moment...…  As its just looking for 'image sharpness', would it work for terrestrial objects ??

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Yes it will work for terrestrial objects. If measures the intensity slope between dark and light areas. This slope will be less when de-focused.  It has been tested successfully on the Moon without seeing the rim, but for testing it terrestrial objects, select a target with some sudden intensity differences.

Focusing on the Sun rim worked also fine, but unfortunately Sun spots are still missing. One focus test on Venus was also successful. Testing on Jupiter or Saturn has to wait till they show up in the night sky.

Han

 

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That's interesting, just out of curiosity, would this work with a manual focuser and tell when the best focus is reached? 

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That's an interesting option we haven't consired. Note that the sharpeness is also depending on the seeing. The autofocus routine is building a curve where sharpness is a function of focuser position. The program will find the best focus position using curve fitting. The curve fitting will cope with the seeing effects. Manually finding the best focus with the sharpness value will be more difficult. You will get litte unstable sharpness values near the best focus position due to the seeing.

Nevertheless this could be an interesting option which is easy to implement. In setting tab FILES there is currently an option "Automatic HFD measurement for every sequence capture"  Something simular could be done if "Planet" autofocus is selected and without sequence. So report the sharpness in the log after each exposure.

I will propose it to Patrick.

later, proposed. See https://www.ap-i.net/mantis/view.php?id=2264

1387125757_hfdmeasurement.png.6a31abdcd2e7560312cc9c728e4ee0e9.png

Edited by han59
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Hi Han ,

Would this (Autofocus on Planets) still work with a DSLR ?  

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Yes it will work with any camera including OSC sensors as found in a DSLR.

The basic principle it pretty simple. It analyses the image on higher frequencies. How sharper the image the more higher frequencies (faster changes in grey) can be found. For practical reasons the focus curve is displayed upside down to make it compatible with a V-curve based on HFD or FWHM.  By default the algorithm groups the pixels in 2x2 so a bayer matrix as found in OSC doesn't have any influence.

Han

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Ok tried it out on last nights moon and with a slight Indi settings dslr camera problem and it seemed to work well. Thanks Parick/Han.

moon1.png

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Thanks for the feedback.

I'm just waiting for a Sun spot & clear day for further testing.

Han

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