It is the test shot with Astro-Physics Stowaway 92mm f/6.6 + field flattener.
It operates at f/7.

Focal length measurement result with shots.

===== Astro-Physcis Stoaway f/6.65 + flattener =====
time: 2019/07/16 20:54:00
diameter: 29.00' 58.62"
degree: 0.499617 degree
radian: 0.008720 radian
pixel width: 813 pixel
pixel pitch: 6.95 micron
image width: 5.65 mm
focal length: 647.98 mm

===== Astro-Physcis Stoaway f/6.65 + flattener =====
time: 2019/07/17 04:15:55
diameter: 30.00' 0.54"
degree: 0.500150 degree
radian: 0.008729 radian
pixel width: 813 pixel
pixel pitch: 6.95 micron
image width: 5.65 mm
focal length: 647.28 mm