A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Greg Rudzinski
Date: 2017 May 24, 08:53 -0700
The image in the AH mirror should remain at infinite focus no matter the distance to the observer. What I have noticed with stars vs. planets is that there is extra fiddling with the focus of the star because of the inherent flickering of direct (vs reflected) star light through the atmosphere. When observing the Sun there should be no need to adjust focus once set using an artificial horizon. Natural horizon observations may need adjusting to find sharpness compromise between body and horizon. During twilight it is easy to unintentionally shift the star image to the edge of the field which will cause fuzzing of the image. Try installing a peep in the ocular of your scope to help keep center field viewing.
P.S. Focus is definitely not on the mirror. This can be recorded using a digital camera where horizon mirror frame is blurred yet reflected body and natural horizon are sharp in the reflection.