N.I.N.A. Meridian Flip Simulator

By Kumar Challa

Visualize how your sub-exposure duration, flip settings, and mount limits interact near the meridian.

3D Sky Visualization

Drag to orbit, scroll to zoom. German equatorial mount at a mid-northern latitude; target transits the zenith. The scenario recomputes live from the settings above. The angular scale is exaggerated for clarity.
Watch the clearance tether between the scope and the pier: if it turns red before the flip fires, your flip settings let the scope get too close. Check your Pause before meridian, Minutes after meridian, and mount limit against your own imaging train.

Angular Sky Visualization

Zenith is the Meridian (straight up). The Calculated Flip Start line shows when the flip will be initiated.
The angular scale is exaggerated for clarity.
Note: NINA itself has no mount-limit setting; it only knows Max. minutes after meridian. Set that below your mount's physical limit. The red ray marks the effective flip deadline: the lower of T2 and the mount limit, treated by this simulator as a hard deadline.

Linear Timing Visualization

Drag the grey time dot on the axis to scrub; the telescope follows in both charts. Download/dither time between subs is not shown.

How NINA decides the last sub

NINA never cuts a sub short to make the flip. The decision happens between exposures: before each new sub, NINA checks whether it can finish before the flip deadline. A sub that fits runs to completion, and a sub that does not fit is simply never started, so the flip begins right after the previous sub ends.