102 mm f/12.7 Maksutov

Entered in AstroDMx as a Skywatcher 102 / 1300 profile. Confirm the exact model and how it was acquired — this entry was written from the capture log, not from the box.

The scale was checked the right way round for once: a circle fitted to the sunlit limb of Venus gave a 155 px disc against a 158 px prediction from the ephemeris at 1300 mm and 1.4 µm pixels. Within 2%.

At 0.222"/px the Dawes limit spans 5 px, so this is comfortably over-sampled — the opposite problem to the 76 mm Newtonian. No Barlow needed; if anything a short run without the full-resolution mode would cost nothing.

Mirror-shift focusing. A 0.1 mm miss at the focuser is 1.3" of blur at f/12.7, which is about the same as the seeing on a mediocre night, so bracket on a star rather than a limb.