CCDciel is free software released under the terms of the
GNU General Public License
Point your telescope somewhere high in the sky and set the Preview exposure time and binning. Click on the Loop button.
If you are way out of focus start first with a long 10-15 seconds exposure time to see some large out of focus stars disk and move the focuser to reduce the size. If you near the correct focus reduce the exposure time to 1 seconds less.
Double click on a star in somewhere the middle of the captured image. Check the recorded star intensity for saturation or have look to the star profile. The intensity value should be smaller then the sensor maximum value of typically 65535. In case of saturation select a fainter star or reduce the exposure time. Checkmark the “Manual focus aid” to magnify the star image.
Use the focuser buttons or manually adjust the focuser to make the star image as small and bright as possible. It could be beneficial to use a very short exposure time to reduce the seeing and have a quick visual feedback.
When ready uncheck “Manual focus aid”.